What Foods Provide Selenium?
Plant foods are the major dietary sources of selenium in most countries throughout the world. The amount of selenium in soil, which varies by region, determines the amount of selenium in the plant foods that are grown in that soil. Researchers know that soils in the high plains of northern Nebraska and the Dakotas have very high levels of selenium. Thus, people living in those regions generally have the highest selenium intakes in the United States. Selenium can also be found in some meats and seafood, and certain nuts, specifically Brazilian nuts, are very good sources of selenium.
RDAs for Selenium
This table shows how much selenium the healthy population should be getting each day:
Should We Worry About Selenium Deficiency?
You probably don’t need to worry about selenium deficiency, if you eat well and/or take a multi-vitamin/mineral. However, Keshan disease, a disease that can cause poor heart function, has been observed in low-selenium areas of China, where dietary intake is less than 19 mcg per day for men and less than 13 mcg per day for women. This intake is significantly lower than the current RDA for selenium. Also, selenium deficiency may affect thyroid function, because selenium is essential for the synthesis of active thyroid hormone. Selenium deficiency is commonly associated with HIV or AIDS, and has been associated with a high risk of death from this disease. Researchers believe that selenium may be important in HIV disease because of its role in the immune system and as an antioxidant. Today, scientists are actively investigating the role of selenium in HIV or AIDS, and see a need for clinical trials that evaluate the effect of selenium supplementation on HIV disease progression. Selenium and Prostate Cancer: Researchers have found that men with low blood levels of selenium are at a greater risk for developing prostate cancer. The large-scale SELECT trial is studying selenium (and vitamin E) to see if they protect against prostate cancer, but the trial does not end until 2013. What’s more, researchers believe selenium deficiency may worsen the effects of iodine deficiency on thyroid function, and that an adequate selenium nutritional status may help protect against some of the neurological effects of iodine deficiency.
Who May Need Extra Selenium?
Folks with gastrointestinal disorders such as Crohn’s disease, or people who have had parts of their small intestines surgically removed, may have impaired selenium absorption. Speak with your physician about possibly supplementing with extra selenium. Furthermore, people looking to use selenium as an antioxidant in megadose form should consult with a health professional. Generally, megadoses are recommended at 200 micrograms and should not exceed 400 micrograms.
What Is the Health Risk of Too Much Selenium?
There is a moderate-to-high health risk of too much selenium—although selenium toxicity is rare in the United States. High blood levels of selenium can result in a condition called selenosis. Symptoms include gastrointestinal upsets, hair loss, white blotchy nails, and mild nerve damage. The Institute of Medicine has set a tolerable upper intake level for selenium at 400 micrograms per day for adults to prevent the risk of developing selenosis. “Tolerable upper intake levels” represent the maximum intake of a nutrient that is likely to pose no risk of adverse health effects in the general population.
