By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Selenium is a mineral that may help to prevent cancer and heart disease. Animals that are made deficient in selenium develop a weakness of their heart muscle, and there is a region in China where women and children develop heart failure (called Keshan disease), which can be prevented by taking selenium.

Selenium is a powerful antioxidant and may act with other antioxidants such as vitamins C and E to protect the body's cells against the ravages of free radicals (unstable chemicals which are by-products of our metabolism), which can promote the development of cancer and heart disease. Selenium may also have an aspirin-like effect that makes blood platelets less likely to stick together and lead to the formation of blood clots.

The selenium in our diets comes from a number of sources, including grains, meat, and fish. The amount varies widely according to how much selenium there was in the soil where the food was grown. The recommended daily intake is 50 micrograms. Selenium can be toxic when taken in doses of more than 750 micrograms a day; symptoms include hair loss, nausea, and fatigue.

Human studies on selenium are relatively few. A Finnish study found that people with low levels of selenium in their blood were at increased risk of heart disease, but other studies have not found this. Smokers have lower levels than non-smokers. Taking selenium supplements may help raise the HDL (good) cholesterol, but this is uncertain. The most interesting study was the Nutritional Prevention of Cancer Study, which was designed to see if taking extra selenium (in a dose of 200 micrograms a day) would prevent skin cancer. It didn't, but other types of cancer were reduced by 40%.

Doctor's comments

Selenium is a substance that could turn out to be quite important for health, particularly heart disease and cancer, but we don't yet know enough about it to make recommendations to take it routinely. There are studies now in progress which we hope will provide some answers.

Where it was published

Neve J. Selenium as a risk factor for cardiovascular diseases. Journal of Cardiovascular Risk 1996;3:42-7.