Vitamins And Minerals

Vitamins and minerals have attracted much attention as possible preventive factors for prostate cancer, with many websites featuring them prominently. But anecdotes heavily outweigh facts. The vitamins and minerals that have been most studied in relation to the prevention of prostate cancer are selenium, vitamin E, vitamin A, beta-carotene, and vitamin D.

• Selenium. Selenium is a trace metal and a necessary component of several enzymes, especially one (glutathione peroxidase) thought to prevent free-radical damage to cell structures. Selenium is thought to work closely with vitamin E and is theorized to have antioxidant properties, enhance immune function, and decrease testosterone. A longitudinal study of aging men in Baltimore reported that men with lower levels of blood selenium were more likely than others to develop prostate cancer. In contradiction, however, the area of the world where men are most likely to be selenium deficient is China, where the incidence of prostate cancer is very low. A large study (SELECT: the Selenium and Vitamin E Cancer Prevention Trial) is under way to assess selenium and vitamin E as preventive factors for prostate cancer, but the results will not be known until 2013.

• Vitamin E. The main component of vitamin E is alpha-tocopherol, which is believed to be an antioxidant that works in conjunction with selenium. Vitamin E was previously thought to help prevent heart attacks, but this property is now in question; one study even concluded that high doses of vitamin E may increase heart attacks. A study in Finland in which men who were smokers were given alpha-tocopherol to see if it would prevent lung cancer found no effect on lung cancer but a 32 percent reduction in prostate cancer. Other studies of vitamin E and prostate cancer have yielded highly conflicting results.8 Fifteen thousand physicians are being studied in the United States to assess the effects of vitamins E and C and beta-carotene on the incidence of prostate cancer, but the results will not be available until 2012.

• Vitamin A and beta-carotene. Vitamin A is essential for cells in the eye having to do with vision. A precursor of vitamin A, beta-carotene is metabolized to a compound that functions as vitamin A. Beta-carotene is closely related to lycopene, the ingredient in tomatoes thought to be responsible for their prostate-cancer preventive effect. Studies linking vitamin A and beta-carotene with prostate cancer have been contradictory, with some reporting a preventive effect and others claiming an increase in the incidence of prostate cancer. A trial of beta-carotene to prevent lung cancer resulted in an increase in lung cancer; in recent years interest in these compounds as cancer preventive agents has markedly decreased.9

• Vitamin D. Formed in the skin by exposure to sunlight, vitamin D is essential for bone formation. Interest in vitamin D and prostate cancer arises from epidemiological observations that prostate cancer is, with some exceptions, more prevalent in northern-latitude nations that get less sunlight and among persons with dark skin that absorbs less sunlight. One study reported that high-dose calcitriol, a form of vitamin D, decreased PSA levels in patients with advanced prostate cancer.10 Additional trials are in progress.

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