Selenium is a mineral that lives in the soil and is taken up by plants. When you eat selenium-containing plants, your body absorbs some of the selenium and uses it for some essential functions. Though selenium is an important mineral for health, your body only needs a very small amount. People with certain medical conditions might benefit from selenium supplements. In addition, topical solutions containing selenium sulfide are used to treat some skin conditions.
Selenium in Diet
How much selenium you take in as part of your diet depends in part on where your food is raised. Soils in some parts of the world naturally contain more selenium and pass this on to the plants and animals raised there. In the United States, Nebraska and North and South Dakota have high levels of selenium in the soil. Elsewhere in the world, parts of Russia and China have low selenium levels in the soil. People who live in areas with low levels of selenium who eat only locally grown food can suffer from selenium deficiency, while people who eat a lot of food from areas with high levels of selenium tend to take in a lot of selenium as part of their diet.
Selenium and Cancer
A Tufts University study in 1997, reported in the July 1997 issue of "Nutrition Reviews," noted a link between low rates of cancer, including skin cancer, in people who lived in areas where the soil had a high selenium content. These people also had relatively high selenium levels in their bodies. The Tufts study gave selenium supplements to people who lived in areas with low selenium soil levels and found that, while the supplements didn't show any effect on skin cancer rates, the rates of other cancers, including lung, colon and prostate cancer, fell. A second study in 2003 that was aimed specifically at skin cancer, reported in the October 2003 issue of the "Journal of the National Cancer Institute"; concluded that selenium supplements had no effect on the incidence of recurrence of people who had previously been diagnosed with basal cell carcinoma, a form or skin cancer. In fact, taking selenium appeared to increase the risk of contracting squamous cell carcinoma, another type of nonmelanoma skin cancer.
Selenium Sulfide
Selenium sulfide is a compound of selenium and sulfur used in ointments and shampoos to treat dandruff, seborrhea and other fungal skin conditions. The solution kills the fungus and acts as a drying agent for the skin. You shouldn't use selenium sulfide on broken or burned skin. Follow package directions carefully. The solution can stain clothing, and if you get any in your eyes or on broken skin, flush the area with water.
Selenium Requirements
The Recommended Daily Allowance of selenium is 55 mcg daily for men and women age 14 and older. Seafood, Brazil nuts, some beef and vegetables are good sources of selenium. For example, 1 oz. of Brazil nuts can contain up to 544 mcg of selenium, and 3 oz. of canned tuna contain about 63 mcg. Most people get all the selenium they need from their diet. Some people with gastrointestinal diseases such as Crohn's disease might have trouble absorbing adequate amounts of selenium. You shouldn't take selenium supplements without a doctor's supervision. Too much selenium can lead to side effects such as hair loss and nerve damage.
References
- University of Maryland Medical Center: Selenium
- "Nutrition Reviews"; "Dietary Selenium Repletion May Reduce Cancer Incidence in People at High Risk Who Live in Areas with Low Soil Selenium"; J.C. Fleet; July 1997
- "Journal of the National Cancer Institute"; "Selenium Supplementation and Secondary Prevention of Nonmelanoma Skin Cancer in a Randomized Trial"; A.J. Duffield-Lillico; October 2003
- University of California San Diego: Selenium Sulfide Topical
- Office of Dietary Supplements: Selenium
