Selenium is a trace mineral — a mineral your body needs in small amounts as compared to macrominerals (like iron and calcium) that your body needs in large amounts. But even a trace mineral can have a big impact on your health.
Selenium deficiency is often seen in places where concentrations of selenium in the soil are low — like China, and parts of Russia. Studies have shown that selenium deficiency may contribute to a host of health issues, including heart disease, thyroid issues, and a weakened immune system. Researchers believe that a selenium deficiency doesn’t usually cause illness by itself, but instead makes the body more susceptible to other illnesses.
Three specific diseases have been associated with selenium deficiency: Keshan disease (an enlarged heart and/or poor heart function in children), Kashin-Beck disease (a disorder of the bones and joints), and Myxedematous Endemic Cretinism (developmental delay).
There may be an important link between selenium and cancer risk. Research suggests that selenium can affect your cancer risk in two ways: as an antioxidant, it can help protect the body from damage done by free radicals. But it may also help prevent or slow tumor growth. As selenium breaks down in the body, the by-products may enhance immune system activity and suppress blood delivery to the tumor.
Some studies have observed that death from cancer is lower among people with high blood levels of selenium. In the United States, the incidence of non-melanoma skin cancers is higher in areas with low selenium content in the soil.
However, not all studies have been so encouraging. A 1982 study found that selenium levels did not seem to predict cancer risk. The SU.VI.MAX study in France and the SELECT study in the United States both found that taking selenium plus another supplement (like vitamins E and C) did not prevent or reduce the risk of prostate cancer in many cases.
There may be a relationship between selenium (and other antioxidants) and heart disease. Some surveys have indicated that there may be a link between low antioxidant intake and high rates of heart disease. Some antioxidants (and selenium is one of them) help limit the oxidation of bad LDL cholesterol — helping to curb plaque build-up in arteries. More studies are needed before we can be sure if selenium supplements would help prevent heart disease.
There may be a relationship between selenium levels in the blood and rheumatoid arthritis — a painful, chronic joint disease. Individuals with rheumatoid arthritis tend to have lower levels of selenium in the blood than those without the disease. It may be that the antioxidant powers of selenium can help control levels of free radicals that attack joint tissue. More studies are needed before we can be sure if selenium supplements would help ease symptoms of rheumatoid arthritis.
Selenium supplements may be useful for people with HIV/AIDS. Selenium deficiency has been associated with decreased immune system function — and HIV and AIDS attack the immune system. Small studies of HIV-positive adults and children have linked selenium deficiency with higher death rates and death at a younger age, which may indicate that selenium deficiency can increase disease progression. Right now, selenium supplements are not a routine part of HIV/AIDS treatment, because more research is necessary. However, selenium supplements are being prescribed by some doctors as part of a treatment plan.