What is Selenium?

Selenium is a trace mineral that our bodies use to produce glutathione peroxidase. Glutathione peroxidase is part of the body's antioxidant defense system; it works with vitamin E to protect cell membranes from damage caused by dangerous, naturally occurring substances known as free radicals.

China has very low rates of colon cancer, presumably because of the nation's low-fat diet. However, in some parts of China where the soil is depleted of selenium, the incidence of various types of cancer is much higher than in the rest of the country. This fact has given rise to a theory that selenium deficiency is a common cause of cancer, and that selenium supplements can reduce this risk.

There is some preliminary evidence that selenium supplements might provide some protection...

Preliminary studies hint that supplemental selenium may help prevent some forms of cancer ; ^{1 2 3 4 5} however, this evidence has a long way to go before it can be taken as reliable. ( See below .)

Selenium is required for a well-functioning immune system. ⁶ Based on this, selenium has been suggested as a treatment for people with HIV . Early studies showed little to no benefit. ⁷ A large trial reported in 2007 reported that use of selenium supplements reduced viral load. ⁸ However, this study suffered from numerous flaws in its statistical methods. For reasons that are not clear, another study found that selenium supplements decreased symptoms of psychological anxiety in patients undergoing highly active retroviral therapy (HAART). ⁹ One study...

Safety Issues

The US Institute of Medicine issues guidelines for the maximum total daily intake of various nutrients, based on estimations of what should be safe for virtually all healthy individuals. These tolerable upper intake levels (ULs) are, thus, conservative guidelines. For selenium, they have been set as follows: ¹⁰

• Infants

• 0-6 months: 45 mcg

• 7-12 months: 60 mcg

• Children

• 1-3 years: 90 mcg

• 4-8 years: 150 mcg

• 9-13 years: 280 mcg

• Males and Females

• 14 years and older: 400 mcg

• Pregnant or Nursing Women: 400 mcg

Note that these dosages apply to combined dietary and supplemental intake of selenium. When deciding how much selenium it’s safe to take, keep in mind that most adults already receive about...