Selenium and CancerSeveral studies have indicated that the antioxidant selenium, found naturally in foods like dairy, eggs, and fish, might help reduce the risk of both prostate and colorectal cancers. However, it’s still too early to recommend taking selenium for this purpose because the research is too preliminary, according to a review of studies published online September 2 in Molecular Nutrition and Food Research.

Considering that prostate and colorectal cancers are two of the most common cancers in this country, it’s not surprising that researchers are seeking new ways to prevent these conditions. Several studies have suggested that selenium might be an effective way to reduce both prostate and colorectal cancer risk.

How might selenium ward off these cancers? There are a few possible mechanisms. In lab studies, selenium appeared to activate genes that suppress tumor formation, as well as trigger the process of programmed cell death (apoptosis) that normally destroys cancer cells. Selenium might also help prevent DNA damage caused by highly reactive molecules known as free radicals. This damage can lead cells to turn cancerous and produce tumors. Finally, selenium appears to reduce inflammation. Chronic inflammation has been linked to the DNA and cell damage that can trigger prostate and colorectal cancers, as well as other types of cancer. The research seems to indicate that selenium is most effective in men with low levels of the antioxidant, and in those who smoke.

The main drawback of the research performed so far on selenium is that the studies have been very small (some with fewer than 50 participants), and selenium’s effects on prostate and colorectal cancer wasn’t the main outcome being studied. A major trial currently underway should shed more light on the subject, and help confirm or deny the benefit of selenium in prostate and colorectal cancer risk.

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) includes more than 35,000 men throughout the country. Study participants have been randomly assigned to receive selenium, vitamin E, selenium and vitamin E, or an inactive pill (placebo). Results are expected in 2013. A couple of smaller studies on the subject are also underway, and their results should be in sooner than SELECT.

Until then, selenium should be part of any balanced diet, but whether people should take supplements specifically for cancer protection is still unclear. “There is no recommendation at this point,” says Ulrike Peters, PhD, MPH, research assistant professor in Epidemiology at the University of Washington School of Public Health and Epidemiology, and lead author of the review. “Generally the recommended daily allowance (RDA) is only 55 micrograms per day; however, the recommendation doesn’t include the amount which is likely to be higher for cancer prevention, because the evidence for cancer prevention wasn’t sufficient when the recommendation was put together.” Most Americans currently meet the RDA for selenium, but for the purposes of cancer prevention, the selenium dose will probably need to be as high as 200 micrograms per day.

If you are interested in taking selenium over the recommended RDA, speak to your doctor or licensed healthcare professional.

Peters U, Takata Y. Selenium and the prevention of prostate and colorectal cancer. Mol Nutr Food Res. 2008;52.

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