If you are taking vitamin E or selenium in the hopes of preventing cancer, you may want to reconsider. A major study has found that supplementation with vitamin E or selenium, alone or in combination, is not associated with a lower risk of prostate cancer or other cancers. This study is published in the January 7 issue of the Journal of the American Medical Association.
According to Statistics Canada, prostate cancer is the leading type of cancer in Canadian men, with an estimated 24,700 newly diagnosed cases and, next to lung cancer and colorectal cancer, prostate cancer is the third leading cause of cancer deaths. An effective prevention strategy for prostate cancer would have substantial public health benefits. Previous studies have suggested a potential role for selenium and vitamin E for the prevention prostate cancer.
Drs. Joseph Chin and Eric Winquist of Lawson Health Research Institute in London, Ontario, along with lead investigators at the University of Texas and other colleagues, conducted the Selenium and Vitamin E Cancer Prevention Trial (SELECT) to examine the long-term effects of selenium and vitamin E, alone or in combination, on the risk of prostate cancer and other health outcomes in men.
The study included 35,533 men, age 50 years or older for African-American men and age 55 years or older for other men at the start of the study, from the U.S., Canada, and Puerto Rico.
Men who participated in this study were randomly assigned to one of four treatment groups receiving two capsules a day between August 2001 and June 2004 for a planned follow up of seven years. One group took 200 micrograms of selenium daily plus an inactive capsule, or placebo, that looked like vitamin E. Another group took 400 milligrams of vitamin E daily along with a placebo that looked like selenium. A third group took both selenium and vitamin E. A final group was given two placebos. Neither the participants, nor the researchers knew who was receiving the selenium and vitamin E, or the placebos.
On September 15, 2008, the independent data and safety monitoring committee recommended the trial be halted early due to the supplements’ inability to prevent prostate cancer. On October 23, 2008, at a median follow-up, participating study sites were informed of the decision and the supplements were discontinued.
The researchers found that there were no statistically significant differences in the number of prostate cancer diagnoses between the four groups.
London, Ontario was one of 12 Canadian SELECT study sites, and one of the seven sites in Ontario. There was strong interest and support for the study by men in the southwest Ontario region and, with just over 1000 participants, the London site was the number three centre for recruitment in North America and the leading site in Canada. London Health Sciences Centre, the London Regional Cancer Program’s Prostate Cancer Centre, and Lawson Health Research Institute were all involved in the study.
"While the overall results of the study have shown that selenium, vitamin E, or selenium plus vitamin E did not prevent prostate cancer, the data underscore a need for discretion when considering the use of natural products such as vitamins for the prevention or control of cancer. These products should undergo the same rigorous investigation as conventional medical treatments,” said Dr. Winquist. “We also need to continue to search for new, effective agents for prostate cancer prevention.”
Although very little is known about why prostate cancer develops, numerous research studies have provided insight into several factors that may play a role. There is a definite link to age: the disease tends to affect men over the age of 50, with 80 per cent of prostate cancers diagnosed in men over age 65. Strong risk factors also include a family history of prostate cancer and a high-fat, low-fiber diet. Men of African descent are also at an increased risk due to genetics.
If prostate cancer is detected early and treated, men have an excellent chance of recovery. Since often there are no symptoms of prostate cancer during very early stages of the disease, it is recommended that every male over age 40 see a physician for regular exams and to discuss screening.
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