TUESDAY, Feb. 28 (HealthDay News) -- While getting the right amount of selenium in your diet can boost your immune function and lower your risk of death, you can get too much of a good thing. Higher-than-normal levels of selenium may contribute to the development of type 2 diabetes, hair loss and certain cancers, a new review of evidence finds.
"There is a U-shaped relationship between selenium intake and health. As selenium intake goes up from a low value, health improves until the bottom of the U-shaped curve is reached, but then adverse -- or even toxic -- effects begin to be seen," said Margaret Rayman, the author of the review of selenium research, and a professor of nutritional medicine at the University of Surrey, in England.
Selenium is a mineral found in a variety of foods. The amount of selenium in foods depends largely on where you live, as the selenium content in the soil varies. Selenium enters the food chain through plants, Rayman said. And, when animals consume the plants, they also consume selenium. Common sources of selenium include Brazil nuts, fish, poultry and wheat. Selenium is also available in supplement form.
Intake of selenium is high in Venezuela, Canada, the United States and Japan, according to background information in Rayman's review, while it's lower in Europe and some areas of China.
The average daily intake recommendations for selenium are 60 micrograms per day for men and 53 micrograms per day for women, according to the research.
For the study, Rayman searched medical literature to find previously completed studies on selenium. The results of that review appear online Feb. 29 in The Lancet.
Rayman found that daily intake of selenium varied from as little as 7 micrograms per day to as much as 4,990 micrograms per day. In Europe, the average intake was 40 micrograms per day, and in the United States, the average d
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