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Selenium is a trace element essential for the human body. There are two different forms of selenium in our diet: organic and inorganic. Organic forms of selenium are found in selenoproteins, meaning the selenium is attached to amino acids within proteins. Inorganic selenium is not bound to proteins. Both are good dietary sources. Selenium has been investigated for its role in prevention of cancer, cardiovascular disease, cognitive decline and thyroid disorders.
Selenium is necessary for DNA synthesis, reproduction and thyroid hormone metabolism. As an antioxidant it protects the body from oxidative damage and provides a cardioprotective benefit by preventing the oxidative modification of lipids and thereby reducing inflammation and preventing aggregation of platelets in the arteries.
Total selenium content of the body ranges from 13 to 30 mg, with approximately 28-46% of this stored in skeletal muscle. Plasma or serum selenium concentrations of 8 µg/dL or higher typically meets needs for selenoprotein synthesis.
Most Americans meet recommendations for selenium intake. Selenium content in the diet varies by region, mostly due to differences in the amounts of selenium found in the soil and thus the local foods available. The Dietary Guidelines for Americans and Institute of Medicine of the National Academies recommends daily allowance (RDA) and tolerable upper intake levels (UL) for different populations based on age.
Brazil nuts are the richest source of selenium in the human diet. Each nut contains about 90 µg selenium, which exceeds the recommended daily allowance. Consumption of Brazil nuts should be limited to avoid selenium toxicity.
Acute selenium toxicity can cause hair loss, muscle tenderness, facial flushing, acute respiratory distress, severe gastrointestinal and neurological issues,Acute selenium toxicity can cause hair loss, muscle tenderness, facial flushing, acute respiratory distress, severe gastrointestinal and neurological issues, myocardial infarction kidney failure and, in extreme cases, death. First signs of chronic selenium toxicity include a garlic odor and metallic taste in the mouth and eventually hair loss and brittle nails. Later symptoms include skin lesions, nausea, diarrhea, skin rashes, irritability, fatigue and nervous system abnormalities.
Selenium in supplement form comes as selenomethionine or selenium-enriched yeast or as sodium selenite. When taken as selenomethionine, the body absorbs about 90%: when taken as selenite, about 50%. Vitamins A, C and E can enhance selenium absorption.
Selenium deficiency is rare in the United States though in combination with environmental stressors, it can predispose people to certain illnesses. For example, a viral infection on top of selenium deficiency can lead to Keshan disease. Deficiency is also associated with male infertility and may exacerbate iodine deficiency, which is closely linked to thyroid problems.
We recommend using the HealthWatch 360 web tool and mobile app to get the most accurate estimate of the nutritional quality and selenium content of your diet. Selenium is only listed on the nutrition facts label when a food item is fortified with this nutrient. Therefore, selenium intake may not always be reflected in your daily report. The best way to get adequate dietary selenium is to eat foods rich in this nutrient.