Thursday, December 18, 2008

Vit. E, selenium don't cut risk of prostate cancer, big study finds

[Source: Arizona Daily Star, Evan Pellegrino] - Two natural supplements that have been promoted as possibly helping prevent prostate cancer actually have no effect, according to a national study that included University of Arizona researchers at the Arizona Cancer Center.

According to the study, vitamin E and selenium supplements do not aid in preventing prostate cancer, the most common cancer in American men other than skin cancers.

The study examined the effects of both supplements in more than 35,000 men nationally, including several hundred in Tucson. It was the largest trial ever on prostate-cancer prevention, according to officials at the Arizona Cancer Center. The study included the Southern Arizona VA Health Care System.

Called SELECT (the Selenium and Vitamin E Cancer Prevention Trial), the study was funded by the National Cancer Institute and coordinated through the Southwest Oncology Group.

"A large trial like SELECT is the only way to determine for certain the real value of supplements," said Frederick Ahmann, professor of medicine and director of the Hematology/Oncology Fellowship Program at the Arizona Cancer Center, in a news release.

"Using science to study and determine whether there is value to taking a specific substance for health or disease prevention is vital, telling us what is helpful, what is harmful and what is not useful to take."

Millions of Americans take dietary supplements such as vitamins, minerals and herbs with the thought that they can help prevent or cure illnesses and ailments.

The Food and Drug Administration considers supplements foods, not drugs, so they don't need to be approved by the FDA before going on the market.

The SELECT study on vitamin E and the trace mineral selenium was based on previous research on other cancers that suggested the supplements might reduce the risk of prostate cancer.

In 1998, a study of 29,133 male smokers in Finland who took vitamin E to prevent lung cancer showed 32 percent fewer prostate cancers. In 1996, a study of 1,312 men and women with skin cancer who took selenium showed that men who took the supplement had 52 percent fewer prostate cancers than those who did not take it, according a National Cancer Institute news release.

Based on these and other earlier findings, men age 50 and older were recruited to participate in SELECT earlier this decade. The men were randomly chosen and grouped to take one of four combinations of supplements or placebos. One group took selenium and vitamin E; one took selenium and a vitamin E placebo; one took vitamin E and a selenium placebo; and the final group received placebos of both supplements.

It was a blinded study — neither the men nor their physicians knew who was taking supplements.

Now, five years after the trial phase of SELECT began, an initial, independent analysis of the study data determined that taking vitamin E and selenium together or alone didn't prevent prostate cancer.

The study actually showed very small increases in the number of cases of prostate cancer in men taking only vitamin E as well as diabetes in men taking only selenium, but researchers dismissed the increase as statistically insignificant.

Participants in the study are being told to stop taking their supplements; however, they will continue to have their health monitored.

Researchers intend to follow the participants for about three years to determine the long-term effects of having taken the supplements.

"As we continue to monitor the health of these 35,000 men, this information may help us understand why two nutrients that showed strong initial evidence to be able to prevent prostate cancer did not do so," said Eric Klein, a study co-chair for SELECT and a physician at the Cleveland Clinic, in the national news release.

The $114 million study was funded by the National Cancer Institute, with additional support from the National Center for Complementary and Alternative Medicine.

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