Some Vitamins May Increase Risk Of Prostate Cancer

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Michael White, professor and department head from the University of Connecticut School of Pharmacy, talks about a new report that says some vitamins can increase your risk of prostate cancer.

Below are some questions with answers provided by White.

What came out of this new clinical trial on mega doses of vitamins?

After several studies of poorer quality showed mega-dose vitamin E and selenium reduced the risk of prostate cancer, a definitive clinical trial called the SELECT Trial was conducted starting in 2001 and enrolled 35,533 healthy men. They were given high-dose vitamin E 400 IU and selenium 200 mcg daily for seven years. In that trial, they found no overall benefits with either vitamin E or selenium compared to placebo in development of prostate cancer.  However, those who started out with the highest levels of selenium before being supplemented had a doubled risk of developing prostate cancer and those with low selenium had a doubling risk of prostate cancer when receiving vitamin E as well. Long story short, antioxidant vitamins like selenium and vitamin E in mega-doses are not protective and may be harmful.

How much higher are the doses of vitamin E and selenium in this study than what is recommended?

The recommended daily allowance for vitamin E is 22 IU and selenium is 55 mcg daily, so between four and 10 times higher than what is recommended.

How can some studies show one thing then another seemingly disputes it? Who should we believe and who is conducting these clinical trials?

You need to understand a little bit about the different types of trials that exist and it will make sense. A large clinical trial like what we just talked about takes thousands of patients and many years to complete. People interested in participating are given an active therapy or matching placebo so they don’t know if they are getting the real thing or not. It costs millions of dollars to complete a trial of this type so only promising ideas will make it to that stage. Poorer quality studies can be done in the laboratory, in animals, or using large databases. Database studies can evaluate things quickly and inexpensively but they have a problem with bias. With antioxidant vitamins, the problem in the early studies was that people who decided to take them were healthier, more active, and more health conscious than those who decided not to. It was these factors, not the antioxidant vitamins that caused the differences. Unfortunately, when the promising results from these poorer quality trials were published in the late 1990s people jumped the gun and started using them before the definitive trials were conducted and it took a decade to find out the truth.

Given the mounting evidence that mega-dose antioxidant vitamins do not protect against cancer, is the Food and Drug Administration going to take action?

They are legislatively prohibited from doing so. In 1972, the FDA wanted to regulate any antioxidant vitamin giving more than 150 percent of the recommended amount because they believed this would result in harm. In 1976, legislation overwhelmingly passed prohibiting their ability to regulate them. So it is up to each American to be aware that there has never been definitive benefits showing mega-dose antioxidants (vitamins E, C, beta-carotene, selenium) do any good and mounting evidence showing they can be harmful. If you take multivitamins, look at the label and if they give more than 100 to 150 percent of the recommended amounts, then stop taking that brand unless you were specifically told otherwise by your doctor. Whether you need to take any multivitamin at all is not known at this time and may depend on whether or not you have a reasonable diet.

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