The Scoop - October 2015

The Scoop: A Newsletter for Consumers from the Office of Dietary Supplements, National Institutes of Health Department of Health and Human Services seal  Office of Dietary Supplements logo

October 2015

In the News

New NIH Research Awards

The NIH Office of Dietary Supplements (ODS), in collaboration with the NIH National Center for Complementary and Integrative Health (NCCIH), is awarding almost $35 million to five centers to study botanicals and other natural products. These centers will investigate the safety of natural products and the ways they might affect human health. These centers will also develop state-of-the-art research technologies. In a related effort, NCCIH is investing about $10 million to establish a new center to study interactions between natural products (including dietary supplements) and drugs.

FDA Warns Consumers About Pure Powdered Caffeine

FDA logo

The U.S. Food and Drug Administration (FDA) has warned consumers to avoid using pure powdered caffeineexternal link disclaimer because these products are potentially dangerous. Although caffeine in doses up to about 400 mg per day is considered safe for most adults, it’s too easy to get a potentially toxic dose when caffeine is used in powdered form. Just one teaspoon of pure powdered caffeine is equal to the amount of caffeine in about 28 cups of regular coffee. The FDA notes that teenagers and young adults, in particular, might be tempted to try powdered caffeine. In fact, in 2014 two healthy young men died after using these products. The FDA has advised consumers to notify the FDA by phone at 240-402-2405 or email at of any adverse events related to use of these products.

Value of Consuming More Calcium Questioned

According to two recent analyses published in the British Medical Journal, getting more calcium, either from food or supplements, doesn’t have a substantial impact on bone mineral density or the risk of fracturing (breaking) a bone.

In one of the analyses, researchers combined data from 72 studies that examined whether getting calcium from either food or supplements affects the fracture risk. More than 75% of the studies that looked at calcium intake from food found that people who got more calcium from food did not have a lower risk of fracturing a bone than those who got less. Studies also showed that taking calcium supplements (with or without vitamin D) decreases the risk of fracturing any bone by 11%, and the risk of fracturing a vertebrae specifically by 14%, but doesn’t affect the risk of fracturing a hip or forearm. However, the quality of the studies varied. When the researchers looked at the four “strongest” studies, the calcium supplements had no impact on the risk of any fractures.

In the second analysis, researchers combined data from 59 studies looking at calcium and bone mineral density (a measure of bone strength). They found that getting more calcium from either food or supplements increases bone mineral density by only a small amount (less than 2%), which is unlikely to affect the risk of fracturing a bone.

Calcium supplements can have possible side effects, so talk with your health care provider about the benefits and risks of calcium supplements to decide if you should take supplements. See our calcium fact sheets for more information.

Study Shows No Benefit of Omega-3 Supplements for Cognitive Decline

According to an NIH-funded study, taking omega-3 dietary supplements does not help prevent cognitive decline in older adults. This study involved approximately 4,000 people who were age 73 on average and at high risk of progressing to advanced age-related macular degeneration. During the 5-year study, some study participants received omega-3 fatty acids while others received a placebo, and all underwent cognitive function tests to assess things such as recall, attention, and memory. The results showed that taking omega-3 supplements did not benefit cognitive function—all participants experienced a similar decline due to normal aging. The study authors note, however, that even though omega-3 supplements don’t appear to help prevent cognitive decline, other studies have shown that consuming foods such as fish, which contain specific nutrients including omega-3s, seems to protect against dementia.

What’s the Scoop? Questions and Answers
About Dietary Supplements

Like many adults, you might take a dietary supplement such as a multivitamin, St. John’s wort, ginkgo, or probiotics. These products are promoted as natural ways to maintain or improve health. But it’s important to know that many of these products might have side effects and can interact with medications. Some can also cause problems during surgery. In this issue of The Scoop, we address several questions you might have about these products.

1. 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?

patient consulting with doctor

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 and information on Coumadin® and vitamin K from the National Institutes of Health (NIH) Clinical Center.

2. 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?

St. John's Wort

Even though dietary supplements from plants are considered 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 health care 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 information on St. John’s wort from the National Center for Complementary and Integrative Health (NCCIH).

3. 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?

hand reaching for supplements

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 health care 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 Understanding Drug-Supplement Interactions from NCCIH.

4. 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?

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 the NIH recognizes that more research is needed on these products. See “In the News” for some of NIH’s latest efforts in this area.

The Scoop provides information from the Office of Dietary Supplements (ODS) on vitamins, minerals, herbs, and other dietary supplement ingredients. The Scoop is not copyrighted and is in the public domain. If you copy or distribute its content, please credit the Office of Dietary Supplements, National Institutes of Health and include the publication title and date. Do not use our information in any way that suggests we endorse any commercial product or service.

We welcome your comments and suggestions for future issues of The Scoop. To contact ODS, go to the Contact Us page of the ODS website. Please note that we cannot answer specific medical questions, make referrals, or provide guidance on the use of dietary supplements. Those questions are best answered by a physician or other qualified health care provider who can tell you if dietary supplements are right for you and what effects they could have on your health.

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The Office of Dietary Supplements (ODS)external link disclaimer is part of the National Institutes of Health (NIH), the nation’s medical research agency----supporting scientific studies that turn discovery into health.

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Office of Dietary Supplements
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