Selenium: An Essential Mineral

You might not know it, but your body needs selenium. Like all trace minerals, it’s essential for proper body functioning, though you need less of them than you do vitamins and minerals needed in larger quantities, such as calcium and iron. That is why it is referred to as a micronutrient.

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Cell Protection

Your body uses selenium to make enzymes called selenoproteins. There are 25 of them, and some of them — such as glutathione peroxidases — work as antioxidants, which are molecules that prevent against cell damage. They protect cells by turning chemicals such as hydrogen peroxide into harmless products like water.

Lower Cancer Risk

According to some studies, selenium deficiency can lead to a higher risk of prostate cancer. One study found that people who took in higher amounts of selenium (159 micrograms (mcg) a day) had a lower risk than those with 86 mcg.

However, while supplements might lower risk of prostate cancer in people with low selenium levels, one study by the National Cancer Institute (NCI) found that for men with already high levels of selenium, supplements only increased the odds of prostate cancer.

Other studies also link selenium levels to lung cancer. In a study of over 9,000 Finnish men and women, low selenium levels were associated with an increased risk of lung cancer. The association was strongest among smokers.

Other Diseases

Some findings suggest that selenium can help lower the risk of cardiovascular disease, but the reasons for this link remain unclear. A study of older Danish men found them to be at risk when their levels were below 79 mcg.

Selenium might also help in the treatment of HIV/AIDS. According to the Linus Pauling Institute, people suffering from the disease normally have declining levels. This is sometimes associated with increased risk of death from HIV. There is not much research on the effects of selenium supplements on people with HIV. One study found that supplements helped to greatly lower hospitalization rates among people with HIV. Another found a decrease in one biological aspect of HIV progression.  

Where to Find It

Selenium is important for good cell health, with potential benefits to people with certain conditions. Selenium deficiency is very rare in the United States and Canada.

The best sources of selenium are organ meats and seafood such as shrimp, crab, and salmon. Selenium content in plants varies and depends on the richness of selenium in the soil. Brazil nuts grown in Brazil and brown rice and noodles from the U.S. are good options.

The recommended dietary allowance (RDA) for selenium is 55 mcg daily for adults, and between 60-70 mcg daily for women who are pregnant or breastfeeding.

While selenium is a necessary mineral, high amounts are toxic. The Food and Nutritition Board (FNB) has set the upper limit of selenium found through food and supplements to 400 mcg a day in adults. As with any supplement, check with a healthcare provider for a level safe for you.