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Vitamins E, C, selenium don't reduce prostate cancer risk

    • American Cancer Society: One in six men will get prostate cancer in his lifetime
    • Studies found antioxidant properties of C, E, selenium didn't fight prostate cancer
    • Men might still get a preventive effect from eating foods high in these vitamins
  • A daily vitamin supplement is not a bad idea, but taking them in large doses for prostate cancer prevention won't help -- and just might harm you.
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Neither selenium nor vitamins C or E reduced the risk of prostate cancer in two studies.

Neither selenium nor vitamins C or E reduced the risk of prostate cancer in two studies.


Previous studies suggested that taking certain vitamins might lower the risk of getting prostate cancer. However, two new studies published in the Journal of the American Medical Association found that men taking these supplements were just as likely to develop prostate cancer as those who weren't taking them.

Questions and answers

What vitamins are we talking about?

Dr. Sanjay Gupta, CNN chief medical correspondent: Researchers looked specifically at vitamins E and C and selenium. For years, many men have been taking these supplements to reduce their risks of prostate cancer, and it made sense since cancer is a result of oxidation damaging your cells, and many vitamins have antioxidant powers.

But two large-scale studies, looking at almost 50,000 men for a total of 13 years, found that men who took these vitamins were just as likely to develop prostate cancer as men who did not take them.

One study looked at vitamin E and selenium, studying over 35,000 men who took 400 IU of vitamin E daily or 200 micrograms of selenium each day, or a combination of the two. A second study looked at 14,000 male physicians who were taking 400 IU of vitamin E every other day or 500 mg of vitamin C daily.

Why did we think these vitamins would help in the first place?

Previous studies suggested that these supplements possibly were working to reduce prostate cancer risks, but those weren't strong studies, their data were conflicting, and they weren't necessarily designed just to look at prostate cancer.

More than half of Americans take supplements, often for disease prevention. These new JAMA studies aren't suggesting that you shouldn't take a multivitamin for general good health. But in cases such as this, where it's solidly proven that specific supplements don't provide a certain health benefit, and we know they could even possibly be harmful, we should be cautious about taking large doses of these vitamins for that purpose, advises Otis Brawley, M.D., chief medical officer of the American Cancer Society.

However, here's a note of hope: We haven't yet ruled out the possibility that even though you can't get a definite benefit from the vitamin supplements, you might still get a preventive effect from eating foods high in these vitamins. So taking mother's advice and eating your broccoli -- still a good idea.

These aren't the first big studies to disprove the efficacy of vitamin supplements for specific diseases. There were two big studies in November 2008 finding no benefit from vitamins E and C against heart disease. Another recent study found vitamin D and calcium don't work against invasive breast cancer.


There's also evidence about how getting hitched helps your chances against prostate cancer, isn't there?

That's right. Another study out this week, published in the journal Cancer Epidemiology, Biomarkers & Prevention, compared single and married men (or those living with a significant other) and found that if you're single, you're 40 percent less likely to get screened for prostate cancer compared with the married guys. That's even if those single men had a family history of prostate cancer.

Beginning at age 50 for average men, and at age 45 if you are at high risk (black men or those with strong family history): Talk to your doctor about prostate cancer screening.

Here are some excerpts from CNN's conversation with the American Cancer Society's Otis Brawley, M.D., who is also CNNhealth's conditions expert doctor:

Unless there are better studies that prove otherwise, doctors should not be prescribing vitamin E or selenium or any other antioxidant supplements to their patients to reduce their risk of prostate cancer.

A good regular multivitamin is still a good thing for general health, especially since we have good evidence for specific benefits. For example, folic acid for women who might get or are pregnant: We know these supplements can help reduce the risk of major birth defects of a baby's spine or brain.

These studies do reiterate something we've already known from other studies: Vitamins for cancer prevention don't really work, and they could be harmful.

This doesn't refute the use of alternative or natural medicines; some natural meds such as aspirin and taxol are highly effective.

But this is a statement of applying evidence-based, scientific research -- meaning these placebo-controlled trials are giving us good, reliable information.

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