Selenium Requirements and Dietary Sources

Fish is an excellent source of selenium.
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Selenium is a trace mineral, which means that your body only needs a small amount. Selenium and proteins combine to form antioxidants called selenoproteins that help protect the cells in your body from free radical damage. Selenium is also essential for normal thyroid function, reproduction, and DNA synthesis.

Selenium is found in many plant-based foods, such as whole grains and nuts, as well as most animal-based foods.

Seafood and organ meats are the richest sources, followed by meats, cereal, and dairy. Eggs, fish, and poultry, contribute a significant amount to the average diet as well.

The National Academies of Sciences, Engineering and Medicine, Health and Medicine Division sets the Dietary Reference Intakes (DRIs) for vitamins and minerals. The DRIs for selenium are based on age -- plus women who are pregnant or breastfeeding need a little more. 

These DRIs reflect the amount of selenium needed by a person in good health -- if you have any medical conditions, you might want to speak to your health care provider about your dietary needs, including selenium.

Dietary Reference Intakes

1 to 3 years: 20 micrograms per day
4 to 8 years: 30 micrograms per day
9 to 13 years: 40 micrograms per day
14+ years: 55 micrograms per day
Women who are pregnant: 60 micrograms per day
Women who are breastfeeding: 70 micrograms per day

Selenium deficiency is rare in developed countries because it's easily obtained from foods. People with some kidney diseases that require hemodialysis and AIDs may be at a higher risk for deficiency. 

Benefits and Side Effects of Taking Selenium Supplements

Some research indicates there may be a lower risk of some forms of cancer and heart disease among people who consume large amounts of selenium in their diets.

But much more research is needed to determine if taking selenium supplements, sometimes marketed as antioxidants, are beneficial. One research study with 100 micrograms selenium indicated taking antioxidant supplements doesn't seem to offer any health benefits.

Selenosis (having too much selenium in your body) results in gastrointestinal symptoms, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage. The National Academy of Sciences set a tolerable upper dietary intake level for selenium at 400 micrograms per day for adults.

Selenium toxicity usually occurs from industrial exposure to selenium and not by taking dietary supplements, but it is possible to ingest too much selenium if you regularly take large doses.

Speak with your doctor before taking large doses of any dietary supplement, including selenium, and follow the directions on the product label.

Sources:

Briançon S, Boini S, Bertrais S, Guillemin F, Galan P, Hercberg S. "Long-term antioxidant supplementation has no effect on health-related quality of life: the randomized, double-blind, placebo-controlled, primary prevention SU.VI.MAX trial." Int J Epidemiol. 2011 Dec;40(6):1605-16. Accessed March 25, 2016. http://ije.oxfordjournals.org/content/40/6/1605.long.

Office of Dietary Supplements - National Institutes of Health. "Dietary Supplement Fact Sheet: Selenium." Accessed March 25, 2016. http://ods.od.nih.gov/factsheets/selenium/.

The National Academies of Sciences, Engineering and Medicine, Health and Medicine Division. "Dietary Reference Intakes Tables and Application." Accessed March 25, 2016. http://www.nationalacademies.org/hmd/Activities/Nutrition/SummaryDRIs/DRI-Tables.aspx.

The United States Food and Drug Administration. "Settlement Reached for Qualified Health Claims Relating Selenium to Reduced Risk of Prostate, Colon, Rectal, Bladder, and Thyroid Cancers," Accessed March 25, 2016. http://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm256940.htm.

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