Selenium is a mineral that your body needs for replenishment of your antioxidant supply, thyroid hormone production and the formation of certain proteins. Most people get selenium from foods in their diet and have low risks for selenium-related problems. However, use of selenium supplements can potentially endanger your health in a number of ways.
Basics
Most people around the world get selenium from plant-based food sources, according to the National Institutes of Health's Office of Dietary Supplements. However, the mineral comes from the soil in which plants grow, and the specific amount of selenium contained in a plant depends on the selenium content of its soil. In the United States, people living in areas with low-selenium soil and plants typically also eat foods from selenium-rich areas, so deficiencies of the mineral rarely occur. Animal-based foods that contain selenium include eggs, tuna, beef, chicken and dairy products such as cheddar cheese and cottage cheese.
Selenium Supplementation
You run a risk of developing a selenium deficiency if you have Crohn's disease or other severe gastrointestinal problems, or have any portion of your stomach surgically removed. You can also deplete your body's selenium supply if you have a severe or widespread infection. In addition, your doctor may recommend selenium supplementation if you have a thyroid disorder called autoimmune thyroiditis, or Hashimoto's thyroiditis. Other proposed, but scientifically unverified, uses of selenium supplements include treatment of heart disease, rheumatoid arthritis, diabetes and several forms of cancer, as well as cancer prevention. Supplemental selenium is available in forms that include sodium selenate, sodium selenite and selenium-enriched yeast.
Toxic Reactions
If your blood levels of selenium rise above 100 mcg/dL, you can develop a toxic condition called selenosis, the Office of Dietary Supplements reports. Potential symptoms of selenosis include gastrointestinal distress, mild nerve damage, garlicky breath, hair loss, white blotches on your nails, irritability, fatigue and skin rashes. In order to prevent possible cases of selenosis, the National Academy of Science's Institute of Medicine has established a safe maximum daily intake of 400 mcg for adolescents and adults. Preteens have a maximum safe intake of 280 mcg per day.
Children between the ages of 4 and 8 have a maximum safe selenium intake of 150 mcg per day, while children between the ages of 1 and 3 have a maximum safe intake of 90 mcg. Between birth and six months, infants have a maximum safe intake of 45 mcg; between six months and one year, the maximum safe intake is 60 mcg.
Additonal Dangers
Use of selenium supplements can cause a variety of additional health problems, including lowered male fertility, worsening of existing cases of hyperthyroidism, increased risks for the onset of prostate cancer and prostate cancer fatality, and increased bleeding risks both during and after a surgical procedure. In addition, selenium use can interfere with or alter the effectiveness of several medications, including anticoagulants, sedatives, warfarin, niacin and the anti-cholesterol drugs called statins. Consult your doctor for more information, especially if you have medical conditions or take medications that increase your selenium-related risks.
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