Selenium is a nutrient that the body needs to stay healthy. Your thyroid gland needs selenium to produce hormones and function properly. Selenium is also needed for reproduction, to make DNA, to help protect cells, and to resist infection.
The amount of selenium that you need each day depends on your age. Average daily recommended amounts are listed below in micrograms (mcg).
| Life Stage | Recommended Amount |
|---|---|
| Birth to 6 months | 15 mcg |
| Infants 7–12 months | 20 mcg |
| Children 1–3 years | 20 mcg |
| Children 4–8 years | 30 mcg |
| Children 9–13 years | 40 mcg |
| Teens 14–18 years | 55 mcg |
| Adults | 55 mcg |
| Pregnant teens and women | 60 mcg |
| Breastfeeding teens and women | 70 mcg |
Selenium is found naturally in many foods, especially foods that contain protein. You can get the recommended amounts of selenium by eating a variety of foods, including:
Selenium is found in multivitamin/mineral supplements and other dietary supplements. It can be present in several different forms, including selenomethionine, selenium-enriched yeast, sodium selenite, and sodium selenate. All dietary supplements include a Supplement Facts label, which will tell you how much selenium is in that product.
Most people in the United States get enough selenium from the foods they eat. However, certain groups of people may have trouble getting enough selenium:
Selenium deficiency is very rare in the United States and Canada. Selenium deficiency can make iodine deficiency worse, increasing the risk of thyroid disease. Selenium deficiency can also cause Kashin-Beck disease (a type of arthritis that can begin in childhood) and Keshan disease (a type of heart disease that occurred mostly in the mid-20th century in China).
Scientists are studying selenium to understand how it affects health. Here are some examples of what this research has shown.
Getting enough selenium from your diet may lower your risk of some forms of cancer, including colorectal, prostate, lung, bladder, skin, esophageal, and gastric cancers.
Selenium supplements have been studied mostly in men to see if they reduce the risk of prostate cancer. These studies have found that selenium supplements do not lower the risk of prostate cancer, especially in men who get enough selenium from their diet.
More research is needed to understand the effects of selenium from food and dietary supplements on cancer risk.
Studies suggest that taking selenium supplements does not reduce the risk of heart disease, especially in people who get enough selenium from food. However, taking combination supplements that contain selenium and antioxidants, such as beta-carotene, vitamin C, or vitamin E, might lower the risk of dying of heart disease.
Some research has shown that people with low selenium levels might have higher risks of cognitive decline and Alzheimer’s disease as they age, although most studies have not found that selenium supplements reduce these risks.
Children and adults with HIV who have selenium deficiency tend to have more severe disease. However, selenium supplements have shown little if any benefit for people with HIV.
While a few studies have found that pregnant women with HIV who take selenium supplements might have a lower risk of preterm birth, no other benefits have been found.
Selenium is an important nutrient for healthy sperm, and research shows that eating a healthy diet can improve sperm quality. However, it is unclear whether selenium supplements improve sperm quality.
More research is needed to determine whether selenium supplements affect male fertility.
Selenium is an important nutrient for the thyroid gland, and selenium levels are higher in the thyroid gland than in any other organ in the body. Research suggests that women who have low levels of selenium have a higher risk of thyroid disease, although a few studies have found that selenium supplements do not provide much benefit for the thyroid.
More research is needed to understand the effects of selenium on thyroid disease.
Yes, if you get too much selenium over time. Brazil nuts, for example, contain very high amounts of selenium (68–91 mcg per nut) and can cause you to go over the upper limit if you eat too many. Getting excessive amounts of selenium from dietary supplements can also be harmful.
Getting too much selenium can cause:
Consuming very high amounts of selenium can cause severe stomach and nervous system problems, difficulty breathing, tremors, lightheadedness, flushing, muscle tenderness, kidney or heart failure, and heart attacks. In rare cases, it can cause death.
The daily upper limits for selenium include intakes from all sources—food, beverages, and supplements—and are listed below. These upper limits do not apply if you are taking selenium under the care of a doctor.
| Ages | Upper Limit |
|---|---|
| Birth to 6 months | 45 mcg |
| Infants 7–12 months | 60 mcg |
| Children 1–3 years | 90 mcg |
| Children 4–8 years | 150 mcg |
| Children 9–13 years | 280 mcg |
| Teens 14–18 years | 400 mcg |
| Adults | 400 mcg |
| Pregnant teens and women | 400 mcg |
| Breastfeeding teens and women | 400 mcg |
Some experts recommend daily upper limits for selenium that are lower than these amounts. For example, in 2023 the European Food Safety Authority set a daily upper limit for selenium of 255 mcg for all adults, with lower amounts ranging from 70 to 230 mcg for children and teens, depending on age.
Yes, selenium may interact with certain medications, and some medications may interact with selenium. For example, cisplatin, a chemotherapy drug that is used to treat cancer, can lower selenium levels, but the effect this has on the body is not clear.
Tell your doctor, pharmacist, and other health care providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if the dietary supplements might interact with your medicines or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.
People should get most of their nutrients from food and beverages, according to the federal government’s Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber, and other components that benefit health. In some cases, fortified foods and dietary supplements are useful when it is not possible to meet needs for one or more nutrients (for example, during specific life stages such as pregnancy). For more information about building a healthy dietary pattern, see the Dietary Guidelines for Americans.
This fact sheet by the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your health care providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.