Selenium

Selenium is an essential trace mineral that the human body cannot produce on its own, making dietary and supplemental intake critical for maintaining normal physiological function. Found naturally in soil, water, and certain foods like Brazil nuts, seafood, and organ meats, selenium is incorporated into over 25 selenoproteins that play key roles in antioxidant defense, thyroid hormone metabolism, and immune system regulation. Because soil selenium levels vary dramatically by region, many people in selenium-depleted areas turn to supplements to help close nutritional gaps. Shoppers most commonly seek selenium for its well-documented role in supporting thyroid health, as the thyroid gland contains the highest concentration of selenium per gram of any tissue in the body. It is also widely used in antioxidant formulas alongside vitamins C and E, where it contributes to the body's natural defense against oxidative stress. Additionally, selenium appears in men's health, fertility, and immune support products due to its involvement in sperm motility and immune cell activity. When comparing selenium supplements, buyers should pay close attention to the form used. Organic forms like selenomethionine and selenium yeast are generally considered more bioavailable than inorganic forms such as sodium selenite or sodium selenate. Dosage is another critical factor — the Recommended Dietary Allowance (RDA) for adults is 55 mcg/day, and the tolerable upper intake level is 400 mcg/day, meaning there is a relatively narrow window between therapeutic and potentially excessive intake. Always check whether a product's selenium content accounts for dietary intake to avoid over-supplementation.