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Frequently Asked Questions (FAQ)

Use and Safety of Dietary Supplements

Q. How do I know if I need a dietary supplement?

A. Many products are marketed as dietary supplements, and it is important to remember that supplements include not only vitamins and minerals, but also herbs and other botanicals, probiotics, fish oil, and other substances.

Some supplements may help ensure that you get adequate amounts of essential nutrients or help promote optimal health and performance if you do not consume a variety of foods, as recommended by MyPlate and the Dietary Guidelines for Americans.

However, dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.

Do not self-diagnose any health condition. Work with your healthcare provider to determine how best to achieve optimal health. Also check with your healthcare provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

Q. Where can I find out how much of each vitamin and mineral I need?

A. To get a list of all vitamins and minerals and how much you need, check out the free online tool from the U.S. Department of Agriculture. Just input a few pieces of information about yourself including your age, height, and weight. You also can get a list of your daily calorie, protein, and other nutritional needs. Keep in mind that the amounts of vitamins and minerals you need include everything you get from food and beverages—you may or may not need a dietary supplement to achieve these amounts. Talk with your healthcare provider to help you determine which supplements, if any, might be valuable for you. For more detailed information about each vitamin and mineral, read our vitamin and mineral fact sheets.

In addition, you can get good sources of information on eating well from the Dietary Guidelines for Americans and ChooseMyPlate.

Q. How can I get more information about a particular dietary supplement such as whether it is safe and effective?

A. Scientific evidence supporting the benefits of some dietary supplements (e.g., vitamins and minerals) is well established for certain health conditions, but others need further study.

Research studies in people to prove that a dietary supplement is safe are not required before the supplement is marketed, unlike for drugs. This is due to the way dietary supplements are regulated by the U.S. Food and Drug Administration (FDA). It is the responsibility of dietary supplement manufacturers/distributors to ensure that their products are safe and that their label claims are truthful and not misleading. If the FDA finds a supplement to be unsafe once it is on the market, only then can it take action against the manufacturer and/or distributor, such as by issuing a warning or requiring the product to be removed from the marketplace.

The manufacturer does not have to prove that the supplement is effective, unlike for drugs. The manufacturer can say that the product addresses a nutrient deficiency, supports health, or reduces the risk of developing a health problem, if that is true. If the manufacturer does make a claim, it must be followed by the statement "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions. Supplements should not replace prescribed medications or the variety of foods important to a healthful diet.

Do not self-diagnose any health condition. Work with your healthcare provider to determine how best to achieve optimal health. Also, check with your healthcare provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

In addition to talking with your healthcare provider about dietary supplements, you can search on-line for information about a particular supplement. It is important to ensure that you obtain information from reliable sources such as:

For tips on evaluating sources of healthcare information on the internet, please see the following document: How to Evaluate Health Information on the Internet: Questions and Answers.

Q. Where can I find information about the use of dietary supplements for a particular health condition or disease?

A. Scientific evidence supporting the benefits of some dietary supplements (e.g., vitamins and minerals) is well established for certain health conditions, but others need further study. Whatever your choice, supplements should not replace prescribed medications or the variety of foods important to a healthy diet.

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.

Do not self-diagnose any health condition. Work with your healthcare provider to determine how best to achieve optimal health. Also, check with your healthcare provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

In addition to talking with your healthcare provider about dietary supplements for a particular health condition or disease, you can search on-line for information. It is important to ensure that you obtain information from reliable sources such as:

For tips on evaluating sources of healthcare information on the internet, please see the following document: How to Evaluate Health Information on the Internet: Questions and Answers.

Q. What does the Supplement Facts label on a dietary supplement tell me?

Sample Supplement Facts label

A. All products labeled as dietary supplements carry a Supplement Facts label that is similar to the Nutrition Facts label found on food products. It lists the active ingredients and their amounts, plus other added ingredients like fillers, binders, and flavorings. It also gives a suggested serving size, but you and your healthcare provider might decide that a different amount is more appropriate for you.

In the Supplement Facts label, the amounts of vitamins, minerals, and other nutrients like dietary fiber are listed as a percentage of the Daily Value or %DV. Each nutrient has one DV that applies to all people age 4 and older. For example, the DV for vitamin C is 90 milligrams (mg) and the DV for the B-vitamin biotin is 30 micrograms (mcg).

The %DV allows you to see how much a product contributes to your approximate daily needs for that nutrient. For example, if a supplement provides 50% of the DV for calcium, it contributes about half of your daily needs for calcium.

The U.S. Food and Drug Administration (FDA) has a webpage that describes the Nutrition Facts label and DV in more detail.

Q. What is the difference between the RDA and DV for a vitamin or mineral?

A. Many terms are used when referring to either the amount of a particular nutrient (such as calcium or vitamin D) you should get or the amount in a food or dietary supplement. The two most common are the Recommended Dietary Allowance (RDA) and the Daily Value (DV). These terms can be confusing.

RDAs are recommended daily intakes of a nutrient for healthy people. They tell you how much of that nutrient you should get on average each day. RDAs are developed by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine. They vary by age, sex, and whether a woman is pregnant or breastfeeding; so there are many different RDAs for each nutrient.

DVs, established by the U.S. Food and Drug Administration (FDA), are used on food and dietary supplement labels. For each nutrient, there is one DV for all people ages 4 years and older. Therefore, DVs aren't recommended intakes, but suggest how much of a nutrient a serving of the food or supplement provides in the context of a total daily diet. DVs often match or exceed the RDAs for most people, but not in all cases.

DVs are presented on food and supplement labels as a percentage. They help you compare one product with another. As an example, the %DV for calcium on a food label might say 20%. This means it has 260 mg (milligrams) of calcium in one serving because the DV for calcium is 1,300 mg/day. If another food has 40% of the DV for calcium, it's easy to see that it provides much more calcium.

The Dietary Supplement Label Database has a webpage that lists the DVs for all nutrients.

Q. What are the Upper Limits (ULs) for vitamins and minerals?

A. Our bodies need vitamins and minerals for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.

Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.

Which vitamins and minerals fall into which category? Here’s the breakdown:

  • Nutrients with ULs: calcium, choline, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, phosphorus, selenium, vitamin B6, vitamin C, vitamin D, and zinc

    Stay under the UL each day for these nutrients to avoid health problems unless your healthcare provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal. The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.

  • Nutrients with ULs, but only from dietary supplements and fortified foods: folate, magnesium, niacin, and vitamin E

    These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.

  • One nutrient with a UL, but only for certain forms: vitamin A

    Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.

    Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.

  • Nutrients with no ULs: biotin, chromium, pantothenic acid, riboflavin, thiamin, vitamin B12, and vitamin K

    These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your healthcare provider recommends it.

Have more questions? See our fact sheets on vitamins and minerals for details about the recommended amounts and ULs.

Q. Where can I report a complaint about a particular dietary supplement or find contact information for a supplement company?

A. To report an illness or injury associated with a dietary supplement, please talk with your healthcare provider and contact the U.S. Food and Drug Administration (FDA).

To report a complaint involving misleading advertising, fraud, or other consumer protection matters associated with a dietary supplement, please contact the Federal Trade Commission (FTC). The FTC also has a helpful webpage with tips for resolving common consumer problems that provides links to state, local and national organizations that might be able to help.

If you are having trouble finding contact information for a dietary supplement manufacturer or distributor, check our Dietary Supplement Label Database. It provides contact information for many dietary supplement companies.

Q. Where can I find free, accurate information about vitamins, minerals, herbs, and other dietary supplements?

A. Good places to start are the ODS dietary supplement fact sheets, which provide helpful information about dietary supplement ingredients including recommended amounts, health effects, safety, and medication interactions. Many of the ODS fact sheets come in three versions—the easy-to-read Consumer version in both English and Spanish, and the more detailed Health Professional version. Read them online or print a copy. In addition, Herbs at a Glance fact sheets from the National Center for Complementary and Integrative Health (NCCIH) provide basic information on specific herbs and botanicals—common names, uses, potential side effects, and resources for more information.

Q. Where can I find published scientific studies about dietary supplements?

A. You can search for medical and scientific studies on specific dietary supplement ingredients using PubMed. PubMed is a database of the National Library of Medicine that provides access to over 30 million journal citations for biomedical literature from MEDLINE, life science journals, and online books.

Vitamins and Minerals

Q. Where can I find out how much of each vitamin and mineral I need?

A. To get a list of all vitamins and minerals and how much you need, check out the free online tool from the U.S. Department of Agriculture. Just input a few pieces of information about yourself including your age, height, and weight. You also can get a list of your daily calorie, protein, and other nutritional needs. Keep in mind that the amounts of vitamins and minerals you need include everything you get from food and beverages—you may or may not need a dietary supplement to achieve these amounts. Talk with your healthcare provider to help you determine which supplements, if any, might be valuable for you. For more detailed information about each vitamin and mineral, read our vitamin and mineral fact sheets.

In addition, you can get good sources of information on eating well from the Dietary Guidelines for Americans and ChooseMyPlate.

Q. I try to eat right, but sometimes I don’t succeed. How do I know if I should take a multivitamin supplement?

A. In most cases it’s best to get nutrients from food first, if you can, before taking supplements. Multivitamin/mineral supplements (MVMs) cannot take the place of eating a variety of foods that are important to a healthy diet. But people who don’t get enough vitamins and minerals from food alone, are on low-calorie diets, have a poor appetite, or avoid certain foods (such as strict vegetarians and vegans) might consider taking an MVM. Healthcare providers might also recommend MVMs to patients with certain medical problems. In addition, certain vitamin and mineral supplements are recommended in specific circumstances as discussed below.

Our fact sheet on MVMs  discusses what types of MVMs are available and possible effects of MVMs on health, and provides guidance on which kind of MVM to choose.

Most research suggests that getting recommended intakes of vitamins and minerals from food—and dietary supplements as needed—promotes health. Our fact sheet points out that some people might benefit from taking certain nutrients found in MVMs. For example:

  • Women who could become pregnant should get 400 mcg/day of folic acid from fortified foods and/or dietary supplements to reduce the risk of birth defects of the brain and spine in their newborn babies.
  • Pregnant women should take an iron supplement as recommended by their healthcare provider.
  • Breastfed infants should receive vitamin D supplements of 400 IU/day until they are weaned. After weaning, infants should drink about 1 quart per day of vitamin D-fortified formula or whole milk.
  • In postmenopausal women, calcium and vitamin D supplements may increase bone strength and reduce the risk of fractures.
  • People over age 50 should get recommended amounts of vitamin B12 from fortified foods and/or dietary supplements because they might not absorb enough of the B12 that is naturally found in food.

Keep in mind that manufacturers add some of the vitamins and minerals found in dietary supplements to a growing number of foods, including breakfast cereals and beverages. As a result, you may be getting more of these nutrients than you think, and more might not be better. Taking more than you need is always more expensive and can increase your risk of side effects.

You may have read about some recent studies suggesting that taking an MVM—or nutrients such as folic acid, copper, and iron—is linked to an increased risk of death. For example, in one study, calcium was the only nutrient that reduced the risk of death. Because the participants in this study were almost all white postmenopausal women, the results cannot be applied to men, younger women, or to people of different ethnicities or races. In addition, the study was not a cause and effect study, so it cannot prove that taking supplements results in dying earlier. Most other studies don’t find a link between taking an MVM or other nutrient dietary supplement and increased risk of death.

To get a personalized list of your nutrient needs, you can use the interactive dietary reference intake tool from the U.S. Department of Agriculture (USDA).

Q. I know that carrots are healthy and have lots of vitamin A. But I’ve also heard that too much vitamin A can be dangerous, so do I need to limit how many carrots I eat?

A. Vitamin A can be toxic at high doses, causing liver damage and birth defects if a woman is pregnant. However, this applies only to the form of vitamin A—called preformed vitamin A or retinol—that is found in foods from animals, such as beef liver, milk, milk products, and some dietary supplements.

Plant foods, such as carrots, spinach, and red peppers, contain a form of vitamin A called beta-carotene. Consuming high amounts of beta-carotene can turn the skin yellow-orange, but this condition is harmless. Beta-carotene does not cause birth defects or the other more serious effects caused by getting too much preformed vitamin A.

So enjoy plenty of carrots and other fruits and vegetables without worrying about getting too much vitamin A. Have more questions? See our fact sheet on vitamin A.

Q. Is it common to need vitamin B12 injections?

A. Vitamin B12 is found naturally in a wide variety of animal foods, including fish, meat, poultry, eggs, and milk. It’s also added to some fortified breakfast cereals and nutritional yeasts.

Most people in the United States get enough vitamin B12 from the foods they eat. Vitamin B12 deficiency is still common, though, affecting up to 15 percent of the population. This is mainly because some people—particularly older adults and those with certain health conditions such as pernicious anemia—have trouble absorbing vitamin B12 from food.

Although many of these people can absorb the synthetic vitamin B12 added to fortified foods and dietary supplements, some can’t. So, it’s possible to have a vitamin B12 deficiency even if you’re getting the recommended amount of vitamin B12 from your diet.

Vitamin B12 deficiency is usually treated with injections, so it goes directly into your body and doesn't have to be absorbed like vitamin B12 taken orally.

Have more questions? See our fact sheet on vitamin B12.

Q. My supplement has 500 mcg of vitamin B12, and the label says that it provides 20830% of the DV. Is that correct? It seems like too much.

A. Yes, the supplement is labeled correctly. The daily value (DV) for vitamin B12 is only 2.4 micrograms (mcg), so a 500-mcg supplement provides 20,830% of the DV. Multivitamin/mineral supplements frequently provide around 100% of the DV for many nutrients, but it is common to find supplements of vitamin B12 (and other B vitamins) that provide much higher doses. Even though most people don’t need such high amounts, vitamin B12 does not have an upper limit, so taking a lot isn’t likely to cause any problems.

Most people consume enough vitamin B12 from the foods they eat, but only animal foods naturally contain vitamin B12. Therefore, vegetarians—especially vegans who eat no animal products—need to get vitamin B12 from either fortified foods, such as many breakfast cereals and nutritional yeast products, or dietary supplements. In addition, some people—especially adults over age 50—have trouble absorbing the form of vitamin B12 that is naturally found in food. For these reasons, as much as 15% of the population might have a vitamin B12 deficiency. Vitamin B12 injections (which are administered by your healthcare provider) or vitamin B12 supplements can help correct a deficiency.

Have more questions? See our fact sheet on vitamin B12.

Q. Can vitamin C prevent colds or make them shorter?

A. This is a common question and one that many scientists have tried to answer. Overall, the research shows that for most people, taking vitamin C regularly does not reduce the chances of getting the common cold. Vitamin C supplements might slightly shorten the duration of a cold and lessen its severity. However, taking vitamin C after the onset of cold symptoms doesn’t appear to help.

Taking too much vitamin C can cause diarrhea, nausea, and stomach cramps. Most adults need between 75 and 90 milligrams (mg) of vitamin C per day and shouldn't get more than 2,000 mg.

Have more questions? See our fact sheet on vitamin C.

Q. Should I take a vitamin D supplement?

A. It depends. You need vitamin D for strong, healthy bones and to help prevent osteoporosis. Researchers are also studying vitamin D to see if it affects your risk of getting diseases such as diabetes and cancer, but they still don't fully understand all of its effects in the body.

Most children and adults should get 15 micrograms (mcg) or 600 International Units (IU) a day, while those age 70 and older need 20 mcg or 800 IU.

Good sources of vitamin D include fatty fish, such as salmon and tuna, and fortified milk. Our bodies also make vitamin D when our skin is exposed to the sun. Knowing exactly how much vitamin D you’re getting can be difficult. Your healthcare provider can help you determine whether you might need a vitamin D supplement based on such factors as the foods you eat, your skin type, and the amount of sun you're exposed to. Your healthcare provider can also test your vitamin D blood levels.

Have more questions? See our fact sheet on vitamin D.

Q. What is the difference between vitamin D2 and vitamin D3?

A. Vitamin D comes in two forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms are well absorbed by the body and increase the amount of vitamin D in your blood. However, vitamin D3 might increase your blood levels of vitamin D slightly more and for longer than vitamin D2.

Have more questions? See our fact sheet on vitamin D.

Q. I am 58 and recently read that I should get 15 mcg (600 IU) per day of vitamin D, but I can’t find a vitamin D supplement that has less than 25 mcg (1,000 IU). Most have 50 mcg (2,000 IU) or even more. Is it safe to take one of these?

A. Younger adults need 15 micrograms (mcg) or 600 International Units (IU) of vitamin D per day, and those over 70 need 20 mcg (800 IU). This includes what you get from foods, beverages, and dietary supplements, and is on top of any vitamin D you may get from sun exposure. Vitamin D is present in a few foods such as fatty fish (like salmon and tuna), fortified milk, beef liver, cheese, egg yolks, and mushrooms, but it can be hard to get enough. Some people have had their vitamin D levels tested and found out they are low.

Unless you are being treated by your healthcare provider, you shouldn’t get more than 100 mcg (4,000 IU) per day of vitamin D. Intakes below this amount are considered safe, so taking a dietary supplement that has 25 mcg (1,000 IU) or even 50 mcg (2,000 IU) should be safe. But we recommend talking with your healthcare provider to determine whether you need a vitamin D dietary supplement, and if so, how much.

Have more questions? See our fact sheet on vitamin D.

Q. I have been taking a vitamin D supplement that contains 400 IU, which is 100% of the DV. I just purchased another vitamin D supplement that also contains 400 IU, but its label says it provides only 50% of the DV. How can that be?

A. There is a simple explanation—the supplement you are currently using has the old Supplement Facts label, and the one you just purchased has the new label. For many years, the DV for vitamin D was 400 IU. Therefore, a vitamin D supplement containing 400 IU would provide 100% of the DV.

However, research shows that many adults need somewhat more vitamin D than previously thought. So, the FDA increased the DV for vitamin D and also changed the units.

The new DV is 20 mcg (micrograms), which is equal to 800 IU. Because the DV has changed, a 400 IU vitamin D supplement bearing the new Supplement Facts label provides only half, or 50%, of the DV.

On the new label, manufacturers must list the amount of vitamin D in mcg, but they can also list it in IU to make the transition a little less confusing for consumers.

Have more questions? See our fact sheet on vitamin D.

Q. My cardiologist recommended a 100 IU supplement of natural vitamin E. I found a supplement that has 100 mg of vitamin E. is that the same as 100 IU?

A. No, 100 milligrams (mg) of vitamin E is not the same as 100 International Units (IU); the units make a difference.

The amount that your cardiologist recommended—100 IU of natural vitamin E—is equal to 67 mg of vitamin E. This is because 1 IU of natural vitamin E is equal to 0.67 mg of vitamin E.

As you noticed, vitamin E is labeled in mg on the new Supplement Facts label instead of IU. It now matches the units used for vitamin E's recommended intake, which is 15 mg for most adults.

Have more questions: See our fact sheet on vitamin E.

Q. I am a 60-year-old woman and have been taking calcium supplements for many years. Recently I’ve heard that they might increase the risk of heart disease. Is that true?

A. Many people, especially women, take calcium supplements. As you know, it is important to get enough calcium (and vitamin D) for good bone health. And although it is often best to get vitamins and minerals from foods and beverages, some supplements can help you get enough of certain nutrients.

Whether calcium affects the risk of cardiovascular disease is not clear. Some studies show that it might protect people from heart disease and stroke. But other studies have found that some people who consume high amounts of calcium, particularly from supplements, might have an increased risk of heart disease.

Much of your risk depends on your diet, lifestyle, current health, and medical and family history. Talk with your healthcare provider about calcium, bone health, and heart disease to figure out what is right for you.

Have more questions? See our fact sheet on calcium.

Q. What is the difference between calcium carbonate, calcium citrate, and other forms of calcium supplements?

A. The main difference between various calcium supplements is the form of calcium they contain, and one isn’t necessarily better than another for you. The two most common forms are calcium carbonate and calcium citrate. Calcium carbonate is absorbed best when taken with food. Calcium citrate is absorbed well on an empty or a full stomach. In addition, people with low levels of stomach acid (which is more common in people aged 50 and older) absorb calcium citrate more easily than calcium carbonate.

One of the most important things to consider about calcium supplements, aside from the form of calcium, is how much to take at one time. The body absorbs calcium best in doses of 500 milligrams (mg) or less at a time. So, for example, if you take 1,000 mg of calcium from supplements per day, you might split the dose and take 500 mg at two separate times during the day.

Have more questions? See our fact sheet on calcium.

Q. Some dietary supplements contain high doses of biotin and are promoted for hair, skin, and nail health. Do they work?

A. Biotin is a B vitamin found mainly in meat, eggs, fish, nuts, and some vegetables. A biotin deficiency can cause skin rashes, hair loss, and brittle nails—hence, the belief that taking extra biotin will produce healthier skin, thick hair, and strong nails. But it’s not clear if these claims hold up.

One of the most common misconceptions about vitamins and minerals is that if a nutrient deficiency causes a particular set of symptoms, then taking more of that nutrient will not only reverse those symptoms but will actually leave you better off. The reality is, if you are already getting enough, getting more doesn’t usually help.

Biotin helps metabolize the food we eat into the energy we need. The recommended amount of biotin for adults is 30 micrograms (mcg) per day, and you can get this much by eating a wide variety of nutritious foods. For example, a meal with 3 ounces of salmon, 3/4 cup of cooked sweet potato, 1/2 cup of cooked spinach, 1/4 cup of roasted almonds, and 1 cup of 2 percent milk provides about 11 mcg of biotin.

Some dietary supplements contain between 2,500 and 5,000 mcg of biotin, which are very high doses. In a few small scientific studies, some people with thin and brittle nails who took high doses of biotin had harder nails. And in a few cases, high doses of biotin improved a rare hair disorder in children and skin rash in infants. But the results of these studies are too preliminary to recommend biotin for any of these conditions.

Biotin doesn’t have an upper intake limit because there’s no evidence that it’s toxic, even at high doses. Most vitamins and minerals, however, do have upper limits, and getting too much can be unsafe. Some can also interact with medications or lab tests. Biotin, for example, can cause false results on some lab tests, including those that measure thyroid hormone levels. For these and other reasons, we always recommend talking with your healthcare provider about vitamins, minerals, and other dietary supplements to help you determine which, if any, may be of value.

Have more questions? See our fact sheet on biotin.

Q. I know that the B vitamin folic acid helps prevent birth defects, so it’s important to take during pregnancy, but why are women supposed to take it before getting pregnant?

A. Yes, getting enough folic acid helps prevent birth defects, especially a kind called neural tube defects. These types of birth defects occur when the neural tube (where the brain and spinal cord form) doesn’t close properly in the fetus.

The neural tube closes very early in pregnancy—only 3 to 4 weeks after conception. This is right around the time most women realize they are pregnant, so waiting to take folic acid until you find out that you are pregnant might be too late.

If you are a woman or teenage girl who could become pregnant, you should get 400 micrograms (mcg) of folic acid per day from dietary supplements and/or fortified foods (such as enriched breads, cereals, pastas, and other grain products). This is in addition to the amount you get naturally from foods and beverages. The recommended amount goes up to 600 mcg per day once a woman is pregnant because folic acid has many other important functions during the remaining months of pregnancy.

Have more questions about folic acid? See our fact sheet on folate.

Q. I am taking a B-100 dietary supplement. It contains very high doses of vitamin B6, vitamin B12, and several other vitamins. Is it safe?

A. Many of the B vitamins—including vitamin B12, thiamin, and riboflavin—do not appear to be harmful at high doses. Therefore, scientists have not established safe upper limits for these nutrients. However, other B vitamins—including niacin and vitamin B6—do have upper limits and can cause problems if you get too much. This is particularly true for vitamin B6 which has an upper limit of 100 milligrams (mg) per day. Getting too much vitamin B6 can cause painful, unsightly skin patches, sensitivity to sunlight, nausea, and heartburn. If you take excessive amounts for a year or more, vitamin B6 can also cause nerve damage that can lead you to lose control of bodily movements. Unless your healthcare provider has recommended a high-dose B vitamin supplement, it’s safest to look for supplements that do not provide amounts at or above the upper limits.

Have more questions? See our fact sheet on vitamin B6 along with our other vitamin and mineral fact sheets.

Q. Can vitamin B6 reduce the symptoms of PMS?

A. Vitamin B6 may be helpful for premenstrual syndrome (PMS), but scientists aren’t sure. Some research shows that taking vitamin B6 supplements (about 80 milligrams [mg] per day) might reduce PMS symptoms including moodiness, irritability, forgetfulness, bloating, and anxiety. But more research is needed to confirm these findings. In addition, it’s important to know that taking too much vitamin B6 as a supplement—more than 100 mg per day for adults—can cause severe nerve damage and other health problems.

If you want to try vitamin B6 for PMS, talk with your healthcare provider first.

Have more questions? See our fact sheet on vitamin B6.

Q. My 17-year-old daughter has decided to follow a vegetarian diet. I’m worried that she’s not getting enough iron. Should she take an iron supplement?

A. Your daughter’s healthcare provider is the best person to help you determine whether she is getting enough iron from her diet or if she might benefit from a supplement.

The daily recommended amount of iron is 15 milligrams (mg) for a teenage girl. Although meat, poultry, and seafood are the richest sources of iron, many plant foods—including beans, nuts, and vegetables—also contain iron. Iron is also added to many fortified breads, cereals, and other grain products.

Vegetarians can get enough iron from foods. However, our bodies don’t absorb the form of iron in plant foods and fortified foods as well as the form of iron found in animal products. For this reason, vegetarians need to consume almost twice as much iron as non-vegetarians.

Our fact sheet on iron provides more details, including the recommended daily amounts of iron for various age groups.

Q. Is magnesium helpful for muscle cramps?

A. As with all vitamins and minerals, it’s important to get enough magnesium for good health. Muscle cramps are one of the signs of a magnesium deficiency, so if you are not getting enough magnesium, getting more might help. But in most cases, muscle cramps are caused by other things. We recommend talking with your healthcare provider to determine if muscle cramps, or any other symptoms you have, might be a sign of a magnesium deficiency or something else.

Have more questions? See our fact sheet on magnesium.

Q. Can magnesium help prevent migraine headaches?

A. Research shows that people who get migraine headaches tend to have lower levels of magnesium than those who don’t. This suggests—but doesn’t prove—that consuming more magnesium might decrease the chance of getting migraines.

According to a few small studies, taking magnesium supplements (about 300 milligrams [mg] twice a day) alone or in combination with medication might help prevent migraines. But this should be done only under the guidance of a healthcare provider because taking too much magnesium as a supplement can cause problems. If you want to try magnesium for migraine headaches, we recommend talking with your healthcare provider.

Have more questions? See our fact sheet on magnesium.

Q. I know bananas contain potassium. Can I get enough potassium by eating a banana every day?

A. Bananas do have a lot of potassium compared to many other foods but eating one banana a day won’t meet your potassium needs alone. A medium banana has about 420 milligrams (mg) of potassium, so you would have to eat at least 6 to 8 bananas to meet the 2,600 to 3,400 mg of potassium that adults should get each day. Obviously, that’s not the best approach. Instead, eat a nutritious variety of foods that contain potassium to ensure you get enough of this important nutrient.

Have more questions? See our fact sheet on potassium.

Q. I can’t find a potassium supplement that provides very much potassium. Why?

A. Most dietary supplements contain less than 100 milligrams (mg) of potassium, which is only about 3 to 4% of the daily recommended amount for adults. This is partly because of reports that some potassium-containing medications may damage the gastrointestinal tract. Although the U.S. Food and Drug Administration (FDA) does not limit the amount of potassium in dietary supplements, they do require warning labels on some medications that contain 100 mg of potassium or more.

Because of the small amounts of potassium in dietary supplements, you can’t rely on them to help meet your potassium needs. This underscores the importance of getting potassium by consuming a nutritious variety of foods.

Have more questions? See our fact sheet on potassium.

Q. Can potassium help lower my blood pressure?

A. Yes, it might. People with low intakes of potassium have an increased risk of high blood pressure, especially if you consume a lot of sodium (salt). Therefore, increasing your potassium intake, along with decreasing sodium intake, might help lower your blood pressure and reduce your risk of stroke. One way to do this is to follow an eating plan called DASH (Dietary Approaches to Stop Hypertension), which emphasizes potassium from fruits, vegetables, and low-fat dairy products. Also, using potassium-containing salt substitutes in place of regular salt helps lower blood pressure. But it’s not clear whether this is because of the increased potassium, reduced sodium, or both.

Have more questions? See our fact sheet on potassium.

Q. Does all salt contain iodine? What about sea salt?

A. Only salt that is labeled as "iodized" contains iodine. Specialty salts such as sea salt, kosher salt, Himalayan salt, and fleur de sel usually contain little or no iodine. For comparison, ¼ teaspoon of iodized salt contains about 75 micrograms (mcg) of iodine, whereas the same amount of non-iodized sea salt contains less than 1 mcg.

Check product labels to see if the salt is iodized or provides iodine (usually listed as "iodide"). But keep in mind that the iodine in salt decreases over time, especially if the salt is stored in a warm, humid location. Because of this, keep your iodized salt in a cool, dry location and purchase a new container occasionally, like at the start of each new year.

Processed foods such as canned soups are rarely made with iodized salt, so even if these foods contain salt, the salt likely doesn't supply any iodine. If the manufacturer does use iodized salt, the salt will be listed as iodized in the ingredient list on the food label.

For more information about iodine, including the health problems that can occur if you get too little or too much, see our iodine fact sheet and talk with your healthcare provider for specific advice.

Q. I am pregnant and follow a vegan diet. Because iodine is present mainly in animal products, how can I get enough?

A. Women who are pregnant need 220 micrograms (mcg) of iodine a day. Most fruits, vegetables, and other plant foods contain very little iodine (usually less than about 7 mcg per serving). So, if you follow a vegan diet or eat few or no dairy products, seaweed, seafood, or eggs, you might not get enough iodine. Also, if you don't use iodized salt, your iodine intake might be low.

Getting too little iodine could affect your baby's development. Because of this, the American Thyroid Association recommends a daily supplement containing 150 mcg of iodine for pregnant and breastfeeding women. Many standard multivitamin/mineral supplements contain iodine, but only about half of prenatal supplements contain iodine. Talk with your healthcare provider to determine what's right for you.

Our iodine fact sheet has more information the important of iodine during pregnancy and infancy.

Q. I am pregnant and my friend told me to make sure I get enough iodine. I’ve never thought about iodine before. How can I make sure I’m getting enough, but not too much?

A. Some pregnant women in the United States might not get quite enough iodine. Iodine has many important roles in the body, including proper bone and brain development. Talk with your healthcare provider about iodine as part of your prenatal care.

Iodine is found naturally in some foods, but amounts vary. Good sources include seaweed, fish and other seafood, and eggs. Iodized salt is another good source of iodine and is readily available in grocery stores. But processed foods, like canned soups, almost never contain iodized salt.

The American Thyroid Association recommends that pregnant and breastfeeding women take dietary supplements containing iodine (150 micrograms [mcg] per day). Many standard multivitamin/mineral supplements contain iodine, but only about half of prenatal supplements contain iodine. 

Keep in mind that it is possible to get too much iodine, and this can cause problems too. The safe upper limit for adults is 1,100 mcg per day, but for most people it is not a concern. For example, a 3-ounce serving of baked cod has about 160 mcg of iodine, and ¼ teaspoon of iodized salt contains about 75 mcg of iodine.

Have more questions? See our fact sheet on iodine.

Q. I have macular degeneration, and my ophthalmologist suggested taking a dietary supplement to preserve my vision as long as possible. Is there research to back this up, and if so, which supplement should I buy?

A. Many dietary supplements promoted for vision or eye health are based on formulations tested in the Age-Related Eye Disease Studies (AREDS), a series of large clinical trials sponsored by the National Institutes of Health. These studies found that among people with age-related macular degeneration (AMD) who were at high risk of developing advanced AMD, supplements containing vitamin E, vitamin C, zinc, copper, and either beta-carotene or lutein plus zeaxanthin helped slow down the rate of vision loss. Adding the omega-3 fatty acids EPA and DHA to the supplements didn’t help, but it didn’t do any harm either.

The types and amounts of ingredients in commercially available eye-health supplements vary. We recommend asking your healthcare provider to make a recommendation. You can also see the specific formulations that were tested in the AREDS studies, along with the study results, on the National Eye Institute website.

Q. I suffer from migraine headaches, and I’ve heard that riboflavin might help. Is riboflavin safe to take for migraines?

A. Riboflavin is a B vitamin that is sometimes called vitamin B2. A number of foods, including eggs, organ meats (such as kidneys and liver), lean meats, low-fat milk, and green vegetables, contain riboflavin. It’s also added to enriched cereals, bread, and grain products.

Some studies show that riboflavin supplements might help prevent migraine headaches, but other studies do not. Even though not all studies agree, several professional societies recommend trying riboflavin because it might be effective and has few side effects. The Canadian Headache Society, for example, recommends 400 milligrams (mg)/day of riboflavin, under the guidance of a healthcare provider, for preventing migraines. This is a very large daily dose, so we advise talking with your healthcare provider about riboflavin and migraines to find out what’s best for you.

Have more questions? See our fact sheet on riboflavin.

Q. Are Brazil nuts a good way to get enough selenium?

A. Yes, Brazil nuts are very high in selenium. But they contain so much selenium that it can be unsafe to eat too many of them.

Like other vitamins and minerals, selenium has a recommended intake and a safe upper limit. Adults should get at least 55 to 70 micrograms (mcg) of selenium, but not more than 400 mcg a day.

One Brazil nut has about 70 to 90 mcg of selenium. So eating one or two Brazil nuts a day is a great way to get enough selenium. But if you eat more than a small handful of Brazil nuts, you could easily go over the upper limit.

Getting too much selenium on a regular basis can cause several problems including an upset stomach, garlic breath odor, hair loss, white blotchy nails, and mild nerve damage.

Have more questions? See our fact sheet on selenium.

Q. Can zinc make your hair grow?

A. Like all vitamins and minerals, it’s important to get enough zinc for good health. In most cases, hair loss is hereditary and is not related to the amount of zinc you consume. But it is true that a zinc deficiency can cause hair loss in otherwise healthy individuals. If you have a zinc deficiency, increasing your zinc intake to correct the deficiency should help. But this doesn’t mean that taking extra zinc will make your hair thicker or longer.

Most people in the United States get enough zinc from the foods they eat, about 8 to 11 milligrams (mg) per day for adults. You can get the recommended amount by eating a variety of foods, including red meat, poultry, oysters and other seafood, beans, nuts, whole grains, and dairy products.

Getting too much zinc—more than 40 mg per day for adults—can cause problems such as nausea, vomiting, and low copper levels. So, the bottom line is, make sure you're getting enough zinc but not too much.

Have more questions? See our fact sheet on zinc.

Q. I recently heard that people can get too much zinc from using denture creams. Is that really possible?

A. Yes. Zinc is present in some denture cream adhesives. Using large amounts of zinc-containing denture creams (well beyond recommended levels) could lead to excessive zinc intake. Too much zinc can cause copper deficiency and nervous system problems, such as numbness and weakness in the arms and legs.

The safe upper limit for zinc is 40 mg per day. Many denture creams have been reformulated so that they don’t contain zinc, but check product labels to be sure.

Have more questions? See our fact sheet on zinc.

Q. What are the Upper Limits (ULs) for vitamins and minerals?

A. Our bodies need vitamins and minerals for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.

Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.

Which vitamins and minerals fall into which category? Here’s the breakdown:

  • Nutrients with ULs: calcium, choline, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, phosphorus, selenium, vitamin B6, vitamin C, vitamin D, and zinc

    Stay under the UL each day for these nutrients to avoid health problems unless your healthcare provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal. The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.

  • Nutrients with ULs, but only from dietary supplements and fortified foods: folate, magnesium, niacin, and vitamin E

    These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.

  • One nutrient with a UL, but only for certain forms: vitamin A

    Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.

    Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.

  • Nutrients with no ULs: biotin, chromium, pantothenic acid, riboflavin, thiamin, vitamin B12, and vitamin K

    These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your healthcare provider recommends it.

Have more questions? See our fact sheets on vitamins and minerals for details about the recommended amounts and ULs.

Herbs and Botanicals

Q. What are botanical supplements and how do they differ from other supplements like fish oil, probiotics, melatonin, and vitamin D?

A. The term “botanical” means “plant,” so botanical supplements contain one or more parts of plants, like the roots of black cohosh or the flowers of echinacea. Botanical supplements, which are often called herbal supplements, are all classified as dietary supplements and they are regulated by the U.S. Food and Drug Administration (FDA) differently than over-the-counter or prescription medicines. Medicines must be approved by FDA before they can be sold or marketed, but dietary supplements do not require this approval.

Have more questions? See our background fact sheet on botanical dietary supplements.

Q. What forms of botanicals are available?

A. Botanicals are sold in many forms as both fresh and dried plant materials. For example, a supermarket’s produce aisle carries fresh ginger root. Dried ginger root may be found in the spice aisle or in the dietary supplement section in capsule or tablet form, in tea bags, or as a liquid preparation. One or more natural plant constituents may also be isolated from a botanical and sold in concentrated form as a dietary supplement, usually in a tablet or capsule. For example, phytoestrogens from soy products are sold as dietary supplements.

Have more questions? See our background fact sheet on botanical dietary supplements.

Q. Do botanical supplements work and are they safe?

A. The amount of scientific evidence on the health effects of botanical supplements varies widely. Because botanical supplements do not require FDA pre-market approval, manufacturers do not have to prove to FDA that their products “work” before selling them. In addition, botanicals aren’t necessarily safe just because they are “natural.” The safety of a botanical depends on many things including its chemical makeup, how it is prepared, the amount used, and whether it is taken with other supplements.

Some botanicals, like St. John’s wort, have been well studied, so scientists know a lot about their safety and effectiveness. Others, like cat’s claw, have not. In addition, botanical supplements can interact with medications, so if you take any medications, check with your healthcare provider. See our dietary supplement fact sheets for more information about the safety and effectiveness of specific botanical supplements.

Have more questions? See our background fact sheet on botanical dietary supplements.

Q. What does the term “standardized” mean on a product label?

A. Manufacturers of botanical supplements can identify and measure specific chemical constituents in their products, often called “markers,” and adjust them to ensure consistent batches. This process is called standardization. However, the constituents responsible for the health effects of most botanicals are not known. In addition, the term “standardized” has no legal or regulatory definition in the United States. Therefore, products labeled as “standardized” aren’t necessarily more effective, safe, or of higher quality than others.

Have more questions? See our background fact sheet on botanical dietary supplements.

Q. How can I find high-quality botanical supplements?

A. Determining the quality of a botanical supplement can be difficult because quality depends on the manufacturer and the production process. Your healthcare provider might be able to recommend a specific brand.

A product’s label doesn’t necessarily indicate quality, but you can look for seals of quality assurance from several independent organizations that offer quality testing. These seals indicate that a product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants. These seals, however, do not guarantee that a product is safe or effective.

Have more questions? See our background fact sheet on botanical dietary supplements.

Q. I get colds a lot, and I’ve thought about trying echinacea. Since it’s a natural herb, it should be safe, right?

A. Not necessarily. Even though herbal products, such as echinacea, are "natural," that doesn't mean that they are always safe or good for you. The safety of an herbal supplement depends on many things, such as its chemical makeup, how it works in the body, how it's prepared, and how much you take. Many supplements contain active ingredients that can have strong effects in the body and can interact with certain prescription drugs in ways that might cause problems.

Always be alert to the possibility of unexpected side effects, especially when taking a new product. Echinacea does not usually cause serious side effects, although it sometimes causes nausea, stomach pain, diarrhea, or vomiting, and allergic reactions can occur.

Unfortunately, study results on echinacea are mixed, so it is not clear at this time whether echinacea prevents or treats upper respiratory tract infections, such as the common cold.

Have more questions? See our background fact sheet on botanical dietary supplements and a fact sheet on echinacea from the National Center for Complementary and Integrative Health.

Q. Is valerian a “natural” form of Valium®? And if so, how much should I take?

A. Although their names are similar, valerian and Valium® are not related to each other. Valium® is a medication available only by prescription. It is the brand name for the drug diazepam which is used to treat anxiety, panic attacks, and other conditions.

Valerian is an herb that is sold as a dietary supplement. It is found in some products promoted as mild sedatives and sleep aids, although it is not clear to what extent valerian is helpful for these conditions. Valerian, like all dietary supplements, should not be taken in place of, or in combination with, prescribed medications without your healthcare provider’s approval.

Like many herbs, scientists are not certain which components of valerian are responsible for its effects. Dietary supplements are not required to be standardized in the United States, so formulations of valerian products may vary. Therefore, it can be difficult to compare one valerian product with another and determine appropriate doses. We recommend talking with your healthcare provider for advice.

Have more questions? See our fact sheet on valerian.

Q. I have been taking a prescription antidepressant but want to try something more natural. A friend told me about St. John’s wort, but I’ve read that it can have side effects. How is this possible since it’s from a plant?

A. Even though dietary supplements from herbs and other plants are "natural," they can still have side effects. They also can interact with prescription or over-the-counter medications. St. John’s wort can cause sensitivity to sunlight and other side effects including dry mouth, dizziness, and headache. It also interacts with a lot of medications including antidepressants, birth control pills, digoxin (a heart medication), indinavir (used to treat HIV/AIDS), and anticoagulants such as warfarin. St. John’s wort usually causes the body to process the medication faster than normal, leading to medication levels that are too low. And taking St. John’s wort with certain antidepressants can lead to a potentially life-threatening increase in serotonin, a naturally occurring substance in the body that helps regulate brain function. Always tell your healthcare providers (including doctors, pharmacists, and dietitians) which dietary supplements you’re taking so that you can discuss what’s best for your overall health.

Have more questions? See a fact sheet on St. John’s wort from the National Center for Complementary and Integrative Health.

Q. My doctor has told me to avoid dietary supplements—especially herbal products—because they haven’t been tested to see if they’re safe and effective. Many people take them or want to try them, so why hasn’t there been more research?

A. Dietary supplements are intended to "supplement the diet;" they're not intended to treat or prevent diseases. Unlike drugs, dietary supplements don't have to undergo premarket review or approval by the U.S. Food and Drug Administration (FDA)—a step that requires a great deal of research—before they become available to the public.

Nevertheless, many dietary supplements can have strong effects in the body, and we recognize that more research is needed on these products. That's one of the reasons we have initiated programs like the Consortium for Advancing Research on Botanical and Other Natural Products (CARBON) program in partnership with the National Center for Complementary and Integrative Health. The CARBON program promotes collaborative, transdisciplinary research on the safety, effectiveness and mechanisms of action of botanical dietary supplements and also supports the development of methods and resources that will enhance the progress of this research.

Have more questions about the CARBON program and our other dietary supplement research initiatives? See our resources for researchers webpage.

Fish Oil and Omega-3s

Q. I’m confused by all of the different terms such as ALA, EPA, and DHA that are used when referring to omega-3s from fish oil, flaxseed, or other sources. What are the differences?

A. There are two main types of omega-3 fatty acids—“short chain” and “long chain,” named for their somewhat different chemical structures. ALA is one of the most common short-chain omega-3s, while EPA and DHA are the most common long-chain omega-3s.

Plant foods such as flaxseed, soybean, and canola oils, as well as chia seeds and black walnuts, contain ALA. Fish and other seafood—especially cold-water fatty fish such as salmon, mackerel, and tuna—contain EPA and DHA.

Most omega-3 supplements, including fish oil, krill oil, cod liver oil, and vegetarian products made from algal oil, contain EPA and DHA. Flaxseed oil supplements contain ALA. Some foods, including certain brands of eggs, yogurt, milk, and soy beverages, contain added omega-3s. You can check product labels to determine which ones.

Most research on the potential health benefits of omega-3s involves EPA and DHA. Our bodies can convert ALA into EPA and DHA, but not very well. So if you want to increase the amount of EPA and DHA you consume, you need to get them from either foods or dietary supplements. If you eat about 8 ounces per week of a variety of seafood, you are getting about 250 mg of EPA and DHA each day. A typical fish oil supplement provides about 300 mg of EPA and DHA, but doses vary widely.

Have more questions? See our fact sheet on omega-3 fatty acids.

Q. Are fish oil supplements recommended for cardiovascular disease? What does the latest research show?

A. Fish oil supplements help lower triglyceride levels, but their other effects on cardiovascular disease are less clear. Studies conducted 10 to 20 years ago found that fish oil reduced the risk of some heart problems such as sudden death and stroke, especially among people with heart disease. But many recent studies have not found the same thing. Some researchers believe that changes in people's lifestyles, such as increased use of statins and higher consumption of fish over the last 10 to 20 years, might overshadow the potential benefits of fish oil. Research clearly shows that eating fish and other seafood as part of a healthy eating pattern reduces the risk of cardiovascular disease. Therefore, experts recommend consuming 8 or more ounces per week of fish and other seafood, including some varieties that have higher amounts of EPA and DHA (such as salmon, mackerel, and tuna).

Have more questions? See our fact sheet on omega-3 fatty acids.

Q. I am pregnant and have heard that it's important to get DHA in addition to prenatal vitamins. Should I take a supplement, eat more fish, or both?

A. During pregnancy, experts recommend eating 8 to 12 ounces of a variety of seafood per week, choosing from varieties that are lower in methyl mercury. These include salmon, herring, sardines, light tuna, and trout. Pregnant women should not consume certain types of fish—such as king mackerel, shark, swordfish, and tilefish—that are high in methyl mercury.

Some studies show that taking DHA or other omega-3 dietary supplements during pregnancy might slightly increase a baby's weight at birth and the length of time the baby is in the womb, both of which might be beneficial. However, it is not clear whether taking these supplements during pregnancy affects a baby’s health or development. We recommend talking with your healthcare provider for advice.

Have more questions? See our fact sheet on omega-3 fatty acids.

Dietary Supplements for Exercise and Athletic Performance

Q. My son plays high school football, and many of his teammates drink energy drinks. Are they safe for teenagers?

A. The main thing to watch out for with energy drinks is the amount of caffeine they contain. Caffeine can cause nervousness, jitteriness, and difficulty sleeping, and at very high doses, it can cause heart problems and can even be fatal.

Caffeine might enhance performance in athletes when taken at moderate amounts before competition (about 200–400 milligrams [mg], depending upon body weight). Many energy drinks contain around 100 mg of caffeine per serving, but some may have more. Most adults can safely consume up to 400 or 500 mg of caffeine (about 4–5 8 oz. cups of coffee) in a day. For adolescents, however, the American Medical Association recommends no more than 100 mg of caffeine a day, and the American Academy of Pediatrics says that children and adolescents should not consume caffeine-containing energy drinks at all.

Have more questions? See the section on caffeine in our fact sheet on dietary supplements for exercise and athletic performance.

Q. I'm training for a marathon and wonder if taking a creatine supplement would be helpful.

A. Creatine is a compound that is stored in your muscles and supplies them with energy. Your body produces some creatine, and you also get some creatine from eating animal foods such as beef and salmon. Creatine supplements provide much larger amounts of creatine (usually in the form of creatine monohydrate) than you can get from your diet.

Creatine supplements can increase strength, power, and the ability to contract muscles for maximum effort. But creatine is helpful only for repeated short bursts of intense, intermittent activity such as sprinting and weight lifting. For endurance activities like distance running, it appears to have little value. Creatine can cause weight gain because it tends to cause water retention, but otherwise, it is considered safe for healthy adults.

Have more questions? See the section on creatine in our fact sheet on dietary supplements for exercise and athletic performance.

Q. I am a 22-year-old male who is trying to build muscle by working out at the gym 4 to 5 days a week. I eat healthy foods, but I wonder if I should take protein powder to make sure I'm getting enough protein.

A. It depends on how much protein you're already getting from the foods you eat. Athletes need about 0.5 to 0.9 grams of protein per pound of body weight a day. This works out to about 90 to 160 grams for someone weighing 175 pounds. This is more protein than less active adults need, but it is still possible to get this amount from protein-containing foods. These include meats, seafood, and poultry (a 3-ounce chicken breast has 27 grams of protein), eggs (one egg has 6 grams of protein), dairy products (1 cup of milk has 8 grams of protein), beans (1/2 cup of black beans has 7 grams of protein), and nuts (1 ounce of peanuts has 7 grams of protein). If needed, protein supplements and protein-fortified food and beverage products can help you get enough protein.

The other thing to consider is the "quality" of protein. Protein is made from amino acids. Your body makes some amino acids but needs to get others (known as essential amino acids or EAAs) from food. Animal foods contain all of the EAAs, but plant foods don't. So if you consume mostly or only plant foods, eat a variety of them to make sure you're getting all EAAs. Most protein powders and drinks contain whey, a protein in milk that provides all of the EAAs.

Have more questions? See the section on protein in our fact sheet on dietary supplements for exercise and athletic performance.

Interactions between Dietary Supplements and Medications

Q. I am taking medications (the blood thinner Coumadin® and an antidepressant) and several supplements (green tea extract, CoQ10, and St. John's wort). Is it OK to take all of these together?

A. No, probably not. Some dietary supplements can cause problems if you take them with prescription or over-the-counter drugs. For example, St. John's wort might interact with certain antidepressants leading to potentially life-threatening seizures, altered heart rate, and unstable blood pressure. Also, St. John's wort, CoQ10, and green tea extract might make blood thinners such as Coumadin® (warfarin) less effective.

These are a few examples of interactions that can occur. If you take medications and also plan to take dietary supplements, talk to your healthcare provider first and be on the lookout for any side effects or problems.

We have a Dietary Supplement and Medicine Record that you can use to keep track of the dietary supplements and medicines you take so you can share this information with your healthcare provider.

Q. My doctor recently put me on the blood thinner Coumadin® and told me to avoid foods like spinach and kale that have a lot of vitamin K. Can you explain why this is necessary and how careful I have to be?

A. Vitamin K has several functions in the body, one of which is to help blood clot normally. Coumadin® (also called warfarin) is a medication that thins the blood, that is, it helps prevent harmful blood clots from forming. It does this by decreasing the activity of vitamin K. Your dose of this medication must be just right so that your blood is not too thin and not too thick. Once your dose is set, the amount of vitamin K you consume will affect how much the medication thins your blood. Your doctor will measure this as your clotting time or "prothrombin time." If you suddenly eat more vitamin K, your blood will thicken; if you suddenly eat less, your blood will get thinner. Both of these situations could be dangerous. So if you take Coumadin® it's important to keep the amount of vitamin K you consume consistent.

Small changes in vitamin K intakes from day to day are inevitable, but larger swings will cause problems. Vegetables, especially leafy green vegetables, such as spinach, kale, turnip greens, collards, and broccoli are particularly high in vitamin K. If you have a spinach salad every day that should be OK, but only if you have it every day. Being that consistent might be hard to do, so doctors sometimes recommend avoiding foods high in vitamin K to be on the safe side. The same is true for any dietary supplements containing vitamin K, including multivitamins If you take one every day, that should be fine, but if you're inconsistent, it could cause problems.

Have more questions or want to see lists of foods that contain vitamin K? See our fact sheet on vitamin K.

Q. I'm scheduled to have surgery in a few weeks, and my surgeon told me to stop taking my dietary supplements. Why is this necessary?

A. Dietary supplements can cause problems during surgery. This can happen in several ways. Some dietary supplements, like garlic, ginkgo, and vitamin E, tend to thin the blood, which can increase how much you bleed during surgery. Some might react with anesthetics, and others might affect blood pressure. All of these can cause unexpected problems during surgery. If you're planning to have surgery, tell your surgeon and other healthcare providers about the dietary supplements you take, and follow their guidance.

Have more questions? See our brochure, Dietary Supplements: What You Need to Know, and Know the Science: How Medications and Supplements Can Interact from the National Center for Complementary and Integrative Health (NCCIH).

Dietary Supplements for Specific Health Conditions

Q. Where can I find information about the use of dietary supplements for a particular health condition or disease?

A. Scientific evidence supporting the benefits of some dietary supplements (e.g., vitamins and minerals) is well established for certain health conditions, but others need further study. Whatever your choice, supplements should not replace prescribed medications or the variety of foods important to a healthy diet.

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.

Do not self-diagnose any health condition. Work with your healthcare provider to determine how best to achieve optimal health. Also, check with your healthcare provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.

In addition to talking with your healthcare provider about dietary supplements for a particular health condition or disease, you can search on-line for information. It is important to ensure that you obtain information from reliable sources such as:

For tips on evaluating sources of healthcare information on the internet, please see the following document: How to Evaluate Health Information on the Internet: Questions and Answers.

Q. Should I take a dietary supplement during the COVID-19 pandemic?

A. Like many people, you might wonder if you should take a dietary supplement to increase your immunity or improve your overall health in these unprecedented times. Some of you have asked us, for example, whether to take zinc or vitamin C, or if copper kills the COVID-19 virus.

There is no scientific evidence that any vitamin, mineral, or other dietary supplement can prevent or cure COVID-19. In fact, the U.S. Food and Drug Administration has issued warning letters to many companies for selling products that claim to prevent, treat, or cure this infection.

Your healthcare provider and the Centers for Disease Control and Prevention (CDC) are the best sources of information on how to protect yourself and others from COVID-19. For zinc, vitamin C, and other nutrients, here's what you need to know:

  • Everyone needs vitamins and minerals for good health. The amounts you need, which are based mainly on your age and sex, include what you get from the foods and beverages you consume, as well as any supplements you take. So, whether you need a vitamin or mineral supplement largely depends on how much you already get from the foods and beverages you consume.
  • Vitamins and minerals have unique roles in the body. Calcium, for example, helps keep your bones strong. Iron is needed to make hemoglobin, which carries oxygen from your lungs to the rest of your body.
  • Our bodies need some nutrients for a healthy immune system. Certain nutrients, including zincvitamin Cvitamin D, and vitamin E help keep your immune system strong. Therefore, if you have a deficiency, your immunity will be lower, and you might be more likely to get sick. But unless you have a deficiency, taking more vitamins and minerals won't increase your immunity. It's like baking bread that needs one packet of yeast. Adding more yeast won't do any good.
  • High doses of some vitamins and minerals can cause health problems. Many vitamins and minerals have "upper limits" because they are unsafe at high doses. Getting too much zinc, for example, can cause nausea and vomiting, and high amounts of copper can cause liver damage. In addition, many nutrients, like vitamin E, can interact or interfere with certain medications.
  • Focus on eating a nutritious variety of foods for good health and a strong immune system. Following a healthy eating pattern that includes fruits, vegetables, whole grains, and protein can help you get the nutrients your body needs.
  • Take a supplement if your healthcare provider recommends it. Talk with your healthcare provider for advice because dietary supplements may be recommended in some circumstances. For example, people who smoke need more vitamin C than nonsmokers; older adults and people with dark skin might not get enough vitamin D; and some vegetarians might not get enough zinc or vitamin B12.

If you decide to take a dietary supplement, check out our fact sheets:

Q. My son has ADHD and I want to avoid using medications. Are there any dietary supplements that might help?

A. Many parents wonder if dietary supplements can help their children with attention deficit hyperactivity disorder (ADHD). Unfortunately, most supplements have not been proven to help people with ADHD and some could be dangerous—so it's important to be careful. If you're considering natural therapies such as dietary supplements for your son, look for information from reliable sources and talk with his healthcare provider.

Vitamins and minerals are some of the most common supplements promoted for ADHD. If your son has a vitamin or mineral deficiency, his healthcare provider might recommend changes to his diet or specific dietary supplements. But beyond that, taking extra vitamins and minerals won't necessarily help. And keep in mind that high doses of some vitamins and minerals can be harmful.

Scientists are studying other dietary supplements, such as fish oil, to see if they hold promise for ADHD. But this research is still in its early stages, so we don't know if these products are effective.

Have more questions? See our dietary supplement fact sheets and information from MedlinePlus on ADHD.

Q. I get colds a lot, and I’ve thought about trying echinacea. Since it’s a natural herb, it should be safe, right?

A. Not necessarily. Even though herbal products, such as echinacea, are "natural," that doesn't mean that they are always safe or good for you. The safety of an herbal supplement depends on many things, such as its chemical makeup, how it works in the body, how it's prepared, and how much you take. Many supplements contain active ingredients that can have strong effects in the body and can interact with certain prescription drugs in ways that might cause problems.

Always be alert to the possibility of unexpected side effects, especially when taking a new product. Echinacea does not usually cause serious side effects, although it sometimes causes nausea, stomach pain, diarrhea, or vomiting, and allergic reactions can occur.

Unfortunately, study results on echinacea are mixed, so it is not clear at this time whether echinacea prevents or treats upper respiratory tract infections, such as the common cold.

Have more questions? See our background fact sheet on botanical dietary supplements and a fact sheet on echinacea from the National Center for Complementary and Integrative Health.

Q. Can vitamin C prevent colds or make them shorter?

A. This is a common question and one that many scientists have tried to answer. Overall, the research shows that for most people, taking vitamin C regularly does not reduce the chances of getting the common cold. Vitamin C supplements might slightly shorten the duration of a cold and lessen its severity. However, taking vitamin C after the onset of cold symptoms doesn’t appear to help.

Taking too much vitamin C can cause diarrhea, nausea, and stomach cramps. Most adults need between 75 and 90 milligrams (mg) of vitamin C per day and shouldn't get more than 2,000 mg.

Have more questions? See our fact sheet on vitamin C.

Q. Some dietary supplements contain high doses of biotin and are promoted for hair, skin, and nail health. Do they work?

A. Biotin is a B vitamin found mainly in meat, eggs, fish, nuts, and some vegetables. A biotin deficiency can cause skin rashes, hair loss, and brittle nails—hence, the belief that taking extra biotin will produce healthier skin, thick hair, and strong nails. But it’s not clear if these claims hold up.

One of the most common misconceptions about vitamins and minerals is that if a nutrient deficiency causes a particular set of symptoms, then taking more of that nutrient will not only reverse those symptoms but will actually leave you better off. The reality is, if you are already getting enough, getting more doesn’t usually help.

Biotin helps metabolize the food we eat into the energy we need. The recommended amount of biotin for adults is 30 micrograms (mcg) per day, and you can get this much by eating a wide variety of nutritious foods. For example, a meal with 3 ounces of salmon, 3/4 cup of cooked sweet potato, 1/2 cup of cooked spinach, 1/4 cup of roasted almonds, and 1 cup of 2 percent milk provides about 11 mcg of biotin.

Some dietary supplements contain between 2,500 and 5,000 mcg of biotin, which are very high doses. In a few small scientific studies, some people with thin and brittle nails who took high doses of biotin had harder nails. And in a few cases, high doses of biotin improved a rare hair disorder in children and skin rash in infants. But the results of these studies are too preliminary to recommend biotin for any of these conditions.

Biotin doesn’t have an upper intake limit because there’s no evidence that it’s toxic, even at high doses. Most vitamins and minerals, however, do have upper limits, and getting too much can be unsafe. Some can also interact with medications or lab tests. Biotin, for example, can cause false results on some lab tests, including those that measure thyroid hormone levels. For these and other reasons, we always recommend talking with your healthcare provider about vitamins, minerals, and other dietary supplements to help you determine which, if any, may be of value.

Have more questions? See our fact sheet on biotin.

Q. I know that the B vitamin folic acid helps prevent birth defects, so it’s important to take during pregnancy, but why are women supposed to take it before getting pregnant?

A. Yes, getting enough folic acid helps prevent birth defects, especially a kind called neural tube defects. These types of birth defects occur when the neural tube (where the brain and spinal cord form) doesn’t close properly in the fetus.

The neural tube closes very early in pregnancy—only 3 to 4 weeks after conception. This is right around the time most women realize they are pregnant, so waiting to take folic acid until you find out that you are pregnant might be too late.

If you are a woman or teenage girl who could become pregnant, you should get 400 micrograms (mcg) of folic acid per day from dietary supplements and/or fortified foods (such as enriched breads, cereals, pastas, and other grain products). This is in addition to the amount you get naturally from foods and beverages. The recommended amount goes up to 600 mcg per day once a woman is pregnant because folic acid has many other important functions during the remaining months of pregnancy.

Have more questions about folic acid? See our fact sheet on folate.

Q. Can vitamin B6 reduce the symptoms of PMS?

A. Vitamin B6 may be helpful for premenstrual syndrome (PMS), but scientists aren’t sure. Some research shows that taking vitamin B6 supplements (about 80 milligrams [mg] per day) might reduce PMS symptoms including moodiness, irritability, forgetfulness, bloating, and anxiety. But more research is needed to confirm these findings. In addition, it’s important to know that taking too much vitamin B6 as a supplement—more than 100 mg per day for adults—can cause severe nerve damage and other health problems.

If you want to try vitamin B6 for PMS, talk with your healthcare provider first.

Have more questions? See our fact sheet on vitamin B6.

Q. Is magnesium helpful for muscle cramps?

A. As with all vitamins and minerals, it’s important to get enough magnesium for good health. Muscle cramps are one of the signs of a magnesium deficiency, so if you are not getting enough magnesium, getting more might help. But in most cases, muscle cramps are caused by other things. We recommend talking with your healthcare provider to determine if muscle cramps, or any other symptoms you have, might be a sign of a magnesium deficiency or something else.

Have more questions? See our fact sheet on magnesium.

Q. Can magnesium help prevent migraine headaches?

A. Research shows that people who get migraine headaches tend to have lower levels of magnesium than those who don’t. This suggests—but doesn’t prove—that consuming more magnesium might decrease the chance of getting migraines.

According to a few small studies, taking magnesium supplements (about 300 milligrams [mg] twice a day) alone or in combination with medication might help prevent migraines. But this should be done only under the guidance of a healthcare provider because taking too much magnesium as a supplement can cause problems. If you want to try magnesium for migraine headaches, we recommend talking with your healthcare provider.

Have more questions? See our fact sheet on magnesium.

Q. Can potassium help lower my blood pressure?

A. Yes, it might. People with low intakes of potassium have an increased risk of high blood pressure, especially if you consume a lot of sodium (salt). Therefore, increasing your potassium intake, along with decreasing sodium intake, might help lower your blood pressure and reduce your risk of stroke. One way to do this is to follow an eating plan called DASH (Dietary Approaches to Stop Hypertension), which emphasizes potassium from fruits, vegetables, and low-fat dairy products. Also, using potassium-containing salt substitutes in place of regular salt helps lower blood pressure. But it’s not clear whether this is because of the increased potassium, reduced sodium, or both.

Have more questions? See our fact sheet on potassium.

Q. Are fish oil supplements recommended for cardiovascular disease? What does the latest research show?

A. Fish oil supplements help lower triglyceride levels, but their other effects on cardiovascular disease are less clear. Studies conducted 10 to 20 years ago found that fish oil reduced the risk of some heart problems such as sudden death and stroke, especially among people with heart disease. But many recent studies have not found the same thing. Some researchers believe that changes in people's lifestyles, such as increased use of statins and higher consumption of fish over the last 10 to 20 years, might overshadow the potential benefits of fish oil. Research clearly shows that eating fish and other seafood as part of a healthy eating pattern reduces the risk of cardiovascular disease. Therefore, experts recommend consuming 8 or more ounces per week of fish and other seafood, including some varieties that have higher amounts of EPA and DHA (such as salmon, mackerel, and tuna).

Have more questions? See our fact sheet on omega-3 fatty acids.

Q. I have macular degeneration, and my ophthalmologist suggested taking a dietary supplement to preserve my vision as long as possible. Is there research to back this up, and if so, which supplement should I buy?

A. Many dietary supplements promoted for vision or eye health are based on formulations tested in the Age-Related Eye Disease Studies (AREDS), a series of large clinical trials sponsored by the National Institutes of Health. These studies found that among people with age-related macular degeneration (AMD) who were at high risk of developing advanced AMD, supplements containing vitamin E, vitamin C, zinc, copper, and either beta-carotene or lutein plus zeaxanthin helped slow down the rate of vision loss. Adding the omega-3 fatty acids EPA and DHA to the supplements didn’t help, but it didn’t do any harm either.

The types and amounts of ingredients in commercially available eye-health supplements vary. We recommend asking your healthcare provider to make a recommendation. You can also see the specific formulations that were tested in the AREDS studies, along with the study results, on the National Eye Institute website.

Q. I suffer from migraine headaches, and I’ve heard that riboflavin might help. Is riboflavin safe to take for migraines?

A. Riboflavin is a B vitamin that is sometimes called vitamin B2. A number of foods, including eggs, organ meats (such as kidneys and liver), lean meats, low-fat milk, and green vegetables, contain riboflavin. It’s also added to enriched cereals, bread, and grain products.

Some studies show that riboflavin supplements might help prevent migraine headaches, but other studies do not. Even though not all studies agree, several professional societies recommend trying riboflavin because it might be effective and has few side effects. The Canadian Headache Society, for example, recommends 400 milligrams (mg)/day of riboflavin, under the guidance of a healthcare provider, for preventing migraines. This is a very large daily dose, so we advise talking with your healthcare provider about riboflavin and migraines to find out what’s best for you.

Have more questions? See our fact sheet on riboflavin.

Q. Can zinc make your hair grow?

A. Like all vitamins and minerals, it’s important to get enough zinc for good health. In most cases, hair loss is hereditary and is not related to the amount of zinc you consume. But it is true that a zinc deficiency can cause hair loss in otherwise healthy individuals. If you have a zinc deficiency, increasing your zinc intake to correct the deficiency should help. But this doesn’t mean that taking extra zinc will make your hair thicker or longer.

Most people in the United States get enough zinc from the foods they eat, about 8 to 11 milligrams (mg) per day for adults. You can get the recommended amount by eating a variety of foods, including red meat, poultry, oysters and other seafood, beans, nuts, whole grains, and dairy products.

Getting too much zinc—more than 40 mg per day for adults—can cause problems such as nausea, vomiting, and low copper levels. So, the bottom line is, make sure you're getting enough zinc but not too much.

Have more questions? See our fact sheet on zinc.

Dietary Supplement Labels

Q. What does the Supplement Facts label on a dietary supplement tell me?

Sample Supplement Facts label

A. All products labeled as dietary supplements carry a Supplement Facts label that is similar to the Nutrition Facts label found on food products. It lists the active ingredients and their amounts, plus other added ingredients like fillers, binders, and flavorings. It also gives a suggested serving size, but you and your healthcare provider might decide that a different amount is more appropriate for you.

In the Supplement Facts label, the amounts of vitamins, minerals, and other nutrients like dietary fiber are listed as a percentage of the Daily Value or %DV. Each nutrient has one DV that applies to all people age 4 and older. For example, the DV for vitamin C is 90 milligrams (mg) and the DV for the B-vitamin biotin is 30 micrograms (mcg).

The %DV allows you to see how much a product contributes to your approximate daily needs for that nutrient. For example, if a supplement provides 50% of the DV for calcium, it contributes about half of your daily needs for calcium.

The U.S. Food and Drug Administration (FDA) has a webpage that describes the Nutrition Facts label and DV in more detail.

Q. When did the new Supplement Facts labels come out and how do they differ from the old labels?

A. Some manufacturers have been using the new labels for a few years, but others didn’t start using them until 2021. This means that you will see both labels on the market for a little while. Here is a look at the new Supplement Facts label for a multivitamin supplement:

Sample Supplement Facts label

Key changes include:

  • Listing vitamin D in mcg (micrograms) instead of international units (IU), although manufacturers can also list IU in parentheses. The units for other nutrients, including vitamin E, vitamin A, and folate, have also changed.
  • New or updated DVs for many nutrients, including 30 mcg for biotin, 90 mg (milligrams) for vitamin C (instead of 60 mg), and 2.4 mcg for vitamin B12 (instead of 6.0 mcg).

Q. I have been taking a vitamin D supplement that contains 400 IU, which is 100% of the DV. I just purchased another vitamin D supplement that also contains 400 IU, but its label says it provides only 50% of the DV. How can that be?

A. There is a simple explanation—the supplement you are currently using has the old Supplement Facts label, and the one you just purchased has the new label. For many years, the DV for vitamin D was 400 IU. Therefore, a vitamin D supplement containing 400 IU would provide 100% of the DV.

However, research shows that many adults need somewhat more vitamin D than previously thought. So, the FDA increased the DV for vitamin D and also changed the units.

The new DV is 20 mcg (micrograms), which is equal to 800 IU. Because the DV has changed, a 400 IU vitamin D supplement bearing the new Supplement Facts label provides only half, or 50%, of the DV.

On the new label, manufacturers must list the amount of vitamin D in mcg, but they can also list it in IU to make the transition a little less confusing for consumers.

Have more questions? See our fact sheet on vitamin D.

Q. My cardiologist recommended a 100 IU supplement of natural vitamin E. I found a supplement that has 100 mg of vitamin E. is that the same as 100 IU?

A. No, 100 milligrams (mg) of vitamin E is not the same as 100 International Units (IU); the units make a difference.

The amount that your cardiologist recommended—100 IU of natural vitamin E—is equal to 67 mg of vitamin E. This is because 1 IU of natural vitamin E is equal to 0.67 mg of vitamin E.

As you noticed, vitamin E is labeled in mg on the new Supplement Facts label instead of IU. It now matches the units used for vitamin E's recommended intake, which is 15 mg for most adults.

Have more questions: See our fact sheet on vitamin E.

Purchasing Dietary Supplements

Q. Where can I purchase dietary supplements?

A. Dietary supplements are available without a prescription through many retail outlets including grocery stores, drug stores, general merchandise retailers, natural food stores, and specialty health and nutrition stores. Many dietary supplements can also be purchased online through the internet.

Q. Which brand(s) of dietary supplements should I purchase?

A. There are a number of factors including price, quality, and availability that may influence your buying decision. The Office of Dietary Supplements (ODS) does not test, analyze, or rate dietary supplements, nor can we recommend certain brands. You may wish to ask your healthcare provider to make a recommendation.

If you have questions about a specific brand of dietary supplements, you can contact the manufacturer for more information. Ask to speak to someone who can address your questions, some of which may include:

  1. What information does the firm have to substantiate the claims made for the product? Be aware that sometimes firms supply so-called "proof" of their claims by citing undocumented reports from satisfied consumers, or graphs and charts that could be mistaken for well conducted scientific research.
  2. Does the firm have information to share about tests it has conducted on the safety or efficacy of the ingredients in the product?
  3. Does the firm follow good manufacturing practices and have a quality control system in place to determine if the product actually contains what is stated on the label and is free of contaminants?
  4. Has the firm received any adverse events reports from consumers using their products?

In addition, several independent organizations offer quality testing and allow products that pass these tests to display a seal of quality assurance that indicates the product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants. These seals do not guarantee that a product is safe or effective.

Organizations that offer quality testing include:*

* Any mention of a specific company, organization, or service does not represent an endorsement by ODS.

ConsumerLab.com, NSF, and USP take different approaches in their testing of dietary supplements and publishing of the results, which are explained on each organization's website. NSF and USP also inspect production facilities to evaluate compliance with The U.S. Food and Drug Administration's (FDA) good manufacturing practices (GMPs) for dietary supplements.

Q. How do I know if the supplement that I purchased contains the ingredients that it claims on the label or if it is contaminated?

A. You should be aware that the U.S. Food and Drug Administration (FDA) does not analyze the content of dietary supplements. However, FDA has issued Good Manufacturing Practices (GMPs) for dietary supplements, a set of requirements and expectations by which supplements must be manufactured, prepared, and stored to ensure quality. Manufacturers are expected to guarantee the identity, purity, strength, and composition of their supplements. For example, the GMPs aim to prevent the inclusion of the wrong ingredients, the addition of too much or too little of a dietary ingredient, the possibility of contamination (by pesticides, heavy metals such as lead, bacteria, etc.), and the improper packaging and labeling of a product.

Some manufacturers use the term "standardized" to describe efforts to make their products consistent. However, U.S. law does not define standardization. Therefore, the use of this term does not guarantee product quality or consistency.

If you have questions about a specific brand of dietary supplements, you can contact the manufacturer for more information. Ask to speak to someone who can address your questions, some of which may include:

  1. What information does the firm have to substantiate the claims made for the product? Be aware that sometimes firms supply so-called "proof" of their claims by citing undocumented reports from satisfied consumers, or graphs and charts that could be mistaken for well conducted scientific research.
  2. Does the firm have information to share about tests it has conducted on the safety or efficacy of the ingredients in the product?
  3. Does the firm follow good manufacturing practices and have a quality control system in place to determine if the product actually contains what is stated on the label and is free of contaminants?
  4. Has the firm received any adverse events reports from consumers using their products?

In addition, several independent organizations offer quality testing and allow products that pass these tests to display a seal of quality assurance that indicates the product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants. These seals do not guarantee that a product is safe or effective.

Organizations that offer quality testing include:*

* Any mention of a specific company, organization, or service does not represent an endorsement by ODS.

ConsumerLab.com, NSF, and USP take different approaches in their testing of dietary supplements and publishing of the results, which are explained on each organization's website. NSF and USP also inspect production facilities to evaluate compliance with The U.S. Food and Drug Administration's (FDA) good manufacturing practices (GMPs) for dietary supplements.

Q. With so many dietary supplements to choose from, how can I compare the ingredients and doses in one product with those in another?

A. The Dietary Supplement Label Database (DSLD) contains label information from thousands of dietary supplement products available in the U.S. marketplace. It can be used to search, for example, for a specific ingredient in a product, a particular supplement manufacturer, text on a label, and a specific health-related claim.

Regulatory Information

Q. Who is responsible for overseeing the regulation of dietary supplements in the United States?

A. In the United States, the U.S. Food and Drug Administration (FDA) has regulatory responsibility for dietary supplements. FDA regulates dietary supplements under a different set of regulations than those covering "conventional" foods and drug products (prescription and over-the-counter). Under the Dietary Supplement Health and Education Act of 1994, the dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. FDA is responsible for taking action against any unsafe dietary supplement product after it reaches the market.

Manufacturers must make sure that product label information is truthful and not misleading. FDA's post-marketing responsibilities include monitoring safety, e.g. dietary supplement adverse event reporting, and product information, such as labeling, claims, package inserts, and accompanying literature.

For more information, contact the FDA Office of Dietary Supplement Programs by email at ODSP@fda.hhs.gov. The physical address of the office is 5001 Campus Drive, College Park, MD 20740.

The Federal Trade Commission (FTC) regulates advertising of dietary supplements in national or regional newspapers and magazines; in radio and TV commercials, including infomercials; through direct mail to consumers; or on the internet. The FTC requires that all information about supplements be truthful and not misleading.

For more information, please contact the FTC via their website.

Q. How do I produce, market, import, distribute or sell a dietary supplement in the United States?

A. The U.S. Food and Drug Administration Office of Dietary Supplement Programs handles all regulatory matters for dietary supplements. Contact them by email at ODSP@fda.hhs.gov or by mail at 5001 Campus Drive, College Park, MD 20740.

Q. When did the new Supplement Facts labels come out and how do they differ from the old labels?

A. Some manufacturers have been using the new labels for a few years, but others didn’t start using them until 2021. This means that you will see both labels on the market for a little while. Here is a look at the new Supplement Facts label for a multivitamin supplement:

Sample Supplement Facts label

Key changes include:

  • Listing vitamin D in mcg (micrograms) instead of international units (IU), although manufacturers can also list IU in parentheses. The units for other nutrients, including vitamin E, vitamin A, and folate, have also changed.
  • New or updated DVs for many nutrients, including 30 mcg for biotin, 90 mg (milligrams) for vitamin C (instead of 60 mg), and 2.4 mcg for vitamin B12 (instead of 6.0 mcg).

Dietary Supplement Sales and Market Data

Q. Where can I locate information or data on dietary supplement sales and usage?

A. The ODS Population Studies Program evaluates the use of dietary supplements by the U.S. population and specific population subgroups and the contributions that dietary supplements make to nutritional status. However, the Office of Dietary Supplements (ODS) does not track dietary supplement sales. You can search for publications on this topic through databases of the scientific literature, including PubMed.

In addition to searching scientific publications, you may wish to contact market research companies that provide sales and marketing data for the nutrition industry.

ODS Website Materials and Link Requests

Q. Can I reproduce fact sheets and other materials found on the Office of Dietary Supplements website?

A. Most of the information available from the Office of Dietary Supplements (ODS) website is within the public domain and, unless stated otherwise, may be freely downloaded and reproduced, provided the content has not been changed or modified. You may also link to individual pages within the ODS website, provided that attribution is made to the ODS and any descriptive notes accurately reflect the content of the page being linked to.

At times the ODS website may contain documents or links to documents, such as full-text journal articles that may be copyright protected. Permission to reproduce copyrighted documents may be required.

Q. Can I add a link to the Office of Dietary Supplements website from my website?

A. The ODS encourages linking to its public web resources. If you wish to link to the ODS website, please direct your link to https://ods.od.nih.gov. If you intend to provide a description with your link, the ODS would prefer the wording:

"The Office of Dietary Supplements, a part of the National Institutes of Health, works to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public about the efficacy and safety of dietary supplements in order to foster an enhanced quality of life and health for the U.S. population."

The abbreviated description "https://ods.od.nih.gov: The website of the Office of Dietary Supplements" is also acceptable.

You may also link to individual pages within this site, provided that attribution is made to the ODS and any descriptive notes accurately reflect the content of the page being linked to.

Q. How can I nominate my website for a link from the Office of Dietary Supplements website?

A. ODS provides links to government-sponsored or government-supported websites that meet the following criteria:

  • Relates to the mission of the ODS;
  • Complements and enhances the information on the ODS website;
  • Provides credible, accurate, current, science-based information;
  • Is subject to adequate procedures for the review and updating of material;
  • Primarily focuses on information or educational content, rather than the promotion of a product or service;
  • Adheres to adequate policies regarding external links and privacy of user data.

These criteria may change to reflect new web policies at the ODS.

If your website meets the above criteria, you may nominate your website for a link from the ODS website by contacting us.

All submissions will be reviewed by ODS staff or external reviewers with expertise in the topic. Currently linked sites undergo periodic re-review. You will receive a decision via email in approximately 1 week.

To provide information from non-government-sponsored or -supported websites to our website visitors, ODS links to the National Library of Medicine website MedlinePlus. MedlinePlus provides good health information for health professionals and consumers from the National Institutes of Health and other trusted sources on over 700 diseases and conditions. If your website provides reliable, science-based information on dietary supplements, we suggest that you contact MedlinePlus to inquire about establishing a link from their website.

Q. How do I know if the information I find on the internet is reliable?

A. The internet has a vast number of websites that provide information about dietary supplements. Much of the information on the internet is useful; however, the internet also allows rapid and widespread distribution of false and misleading information. When evaluating a website, consider the credibility of the source of the information, the purpose of the site, and whether the information is up to date. ODS has a fact sheet to help you decide if the information on a website or in an email is reliable. It is called, How to Evaluate Health Information on the Internet: Questions and Answers.

You can also read a fact sheet on dietary supplements from the Federal Trade Commission (FTC) that includes tips for recognizing fraudulent advertising claims—especially those that claim to cure diseases. Under federal law, dietary supplements cannot be promoted for the prevention or treatment of a disease. To report a health product you believe is falsely advertised, contact the FTC at 1-877-FTC-HELP (1-877-382-4357) or online at https://reportfraud.ftc.gov/.

Media Inquiries

Q. I am with the media and would like to talk with someone from the Office of Dietary Supplements about my dietary supplement questions. How should I proceed?

A. If you need information you haven’t found on our website, or if you wish to request an interview, please send an e-mail to ODSMedia@mail.nih.gov (for media inquiries only). In the body of the e-mail, include your questions, affiliation and deadline. This allows us to research your questions and have the appropriate staff member contact you. We will make every effort to meet your deadline. Please see our Media Contacts webpage for more details or to contact other Federal Government media offices.

Reviewed: June 10, 2021