Selenium's Support for a Healthy Prostate
Though few studies have offered much insight into what causes prostate cancer, a number of researchers have found evidence suggesting that dietary selenium helps support a healthy prostate.
A trace mineral, selenium is found in seafood, meat (especially organ meats such as kidney and liver), plant foods like rice and wheat, and Brazil nuts. It is an antioxidant that has been shown in scientific studies to enhance many aspects of immune function, help protect against a number of chronic disease and control cell damage that can lead to cancer.
One of the first studies making the link between selenium and prostate cancer prevention was the Nutritional Prevention of Cancer Trial, published in 1996 in the Journal of the American Medical Association. The study included 1,312 men and women who had skin cancer. Men who took selenium to prevent nonmelanoma skin cancer received no benefit from selenium in preventing skin cancer; however, men who had taken selenium for six-and-a-half years had approximately 60 percent fewer new cases of prostate cancer than men who took a placebo. This discovery is one of the reasons selenium is being studied in the ongoing Selenium and Vitamin E Cancer Prevention Trial, commonly referred to as SELECT.
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Another study published in the International Journal of Cancer found that among 445 American men, high blood concentrations of selenium appeared to reduce by 30 percent the risk that a man would develop prostate cancer.
As a powerful antioxidant, selenium has the ability to suppress biologically damaging reactions triggered within the body by naturally produced chemicals called oxidants. Because oxidant damage has been linked with many cancers, scientists suspect that any anticancer benefit from selenium could be traced to its antioxidant characteristics and its ability to protect cells from DNA damage or repair cells already damaged.
In 2003, David J. Waters of Purdue University and his colleagues reported a link between selenium and prostate cancer prevention by studying the prostate health in beagles (a species that, like men, appears to develop prostate cancer at rates that increase with age). The scientists supplemented the diets of 38 male dogs, physiologically equivalent to 65-year-old men, with either selenomethionine or high-selenium yeast. Another 10 dogs were put on the same diet, but with no selenium supplements.
After seven months, the researchers sampled blood from each of the animals and examined their prostate glands. The results, published in the Journal of the National Cancer Institute, showed far less DNA damage in the white blood cells and the prostate tissue of dogs treated with selenium than in the untreated group. In fact, 79.1 percent of the prostate cells examined from untreated dogs had "extensive DNA damage" compared with 57.2 percent of such cells from dogs getting supplemental selenium.
Waters' team believes selenium goes beyond its antioxidant effect and actually has more to do with helping cancer cells die. Normal cells develop, grow old and then die, explains Waters. Cancer cells, however, don't die naturally and continue to produce endless offspring. Consequently, cancer cells would pose far less of a problem if the 'suicide switch' that is within normal cells could be turned on in cancer cells. This self-destructive cell death is called apoptosis.
In Waters' study, researchers found roughly twice the level of apoptosis occurring within the prostate tissue of selenium-supplemented dogs as in the untreated ones. Specifically, areas of high apoptosis appeared in 16 of the 38 dogs on a selenium-enhanced diet (42 percent) but in just one of the 10 dogs in the control group. "The idea here is that the cells that are most DNA damaged - and presumably have the highest propensity to turn cancerous - may be selectively purged in the presence of [supplemental] selenium," says Waters.
