A new study of the Journal of Urology compared 52 men who had prostate cancer with 96 men of similar age without evidence of prostate disease. For each, blood samples from roughly four years prior to the study (and before development of prostate cancer) were analyzed for selenium concentration.
The men with the lowest blood levels of selenium were found to be four to five times as likely to develop prostate cancer over the next four years as were the men with the highest blood levels of selenium. The authors concluded that selenium supplementation may be beneficial for the prevention of prostate cancer.
Prostate cancer is one of the major health concerns facing aging men. Any intervention that could help prevent this disease would, therefore, be an important advance.
Selenium is an essential trace mineral found in foods. The recommended dietary allowance for selenium is 55 mcg per day. Good food sources of selenium include seafood, grains, meat, garlic, mushrooms and asparagus. The amount of selenium in plant foods is highly dependent on the selenium content of the soil in which it was grown.
Supplementation with excessive amounts of selenium can cause hair loss and nail sloughing; in rare cases, neurological problems and even death have resulted from taking too much selenium. A recent report from the National Academy of Sciences selected 400 mcg per day as the tolerable upper limit for selenium supplementation. The best form of selenium for supplementation is still open for debate, although previous cancer prevention studies have used high-selenium brewer's yeast.