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Director's Comments Transcript: Vitamin E, Selenium & Prostate Cancer 12/08/2008

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Greetings from the National Library of Medicine and

Regards to all our listeners!

I'm Rob Logan, Ph.D. senior staff National Library of Medicine substituting this week for Donald Lindberg, M.D, the Director of the U.S. National of Medicine.

Here is what's new this week in MedlinePlus.

To listen to Dr. Lindberg's comments, click herelisten

A major clinical trial of 35,000 men was canceled recently after findings revealed that taking vitamin E and selenium together or separately did not result in the prevention of prostate cancer and might do more harm than good.

The clinical trial, sponsored by the National Cancer Institute and the National Center for Complementary and Alternative Medicine, was cancelled about three years early after findings revealed an increase in the number of prostate cancer cases among the men who took vitamin E (compared to a placebo). The men who took selenium in the trial did not experience an increase in prostate cancer rates, but there was an increase in diabetes within this group (compared to those who took a placebo).   

The increased number of prostate cancer cases among the men who took vitamin E and the rise in diabetes cases among participants who took selenium was not statistically significant, so the increases may have occurred by chance.

Nevertheless, the National Cancer Institute and National Center for Complementary and Alternative Medicine decided to end part of the clinical trial because there was no evidence that vitamin E and selenium reduced prostate cancer, which was one of the broader study's underlying purposes.

Trial participants either took placebos, or 200 micrograms of selenium, and 400 milligrams of vitamin E daily. Selenium and vitamin E are antioxidants that exist in small amounts within some foods. Selenium and vitamin E supplements are sold without a prescription and are available in stores throughout the U.S. However, the dose within the pills found on some store shelves sometimes is lower than the levels taken by the trial participants. A price check of some national drug stores revealed selenium costs from about $4.65 to $8.49 a bottle while vitamin E costs vary similarly.

Full disclosure: the National Cancer Institute and the National Center for Complementary and Alternative Medicine are sister institutions to the National Library of Medicine; all are part of the U.S. National Institutes of Health.

The 35,000 male participants in the clinical trial, age 50 or older, were asked to stop taking the supplied medications. However, other parts of the study will continue. For example, participants will receive follow up medical exams in order to study the long term effects of taking vitamin E and selenium. Contrary to some news reports that implied the research that underlay the trial was finished, future participant blood samples will enable researchers to assess how prostate, other cancers, and aging occur at the molecular level.

The trial and larger study are managed by the Southwest Oncology Group, an international network of research institutes with more than 400 clinical sites in the U.S., Canada, and Puerto Rico. The recruiting for the prostate cancer trial began in 2001 and ended in 2004.

You can find out more about the trial by going to NLM's and typing in 'prostate cancer and vitamin E' in the search box -- accessible by clicking 'search for clinical trials' on the front page.

Of course, the findings that vitamin E and selenium are ineffective in preventing prostate cancer are disappointing to the researchers plus many current and future male patients. The trial was initiated based on previous evidence from smaller studies in 1998 and 1996 that the inexpensive and widely available nutrients might be effective. However, few previous studies directly tested the impact of both selenium and vitamin E on prostate cancer.

For example, in the 1998 study, which took place in Finland, about a third of 29,000 men who took vitamin E to prevent lung cancer experienced an unexpected decline in prostate cancer.

To put the current findings in context, prostate is the third most common form of cancer for men of all ages. There will be an estimated 186,320 new cases and an estimated 28,660 men will die from prostate cancer in the U.S. this year. While all men are at risk for prostate cancer, men who are 55 years and older, African-American males, and men with a father or brother with prostate cancer have an elevated risk.

MedlinePlus' prostate cancer health topic page  explains the prostate is the gland below a man's bladder that produces fluid for semen. While treatments for prostate cancer have improved patient health outcomes (especially if detected early), the Prostate Cancer Foundation explains clinical intervention sometimes results in debilitating side effects, such as incontinence and impotent. The Prostate Cancer Foundation report can be found in the 'overviews' section of MedlinePlus' prostate cancer health topic page.

Other resources on's comprehensive prostate cancer health topic page include information about: diagnosis/symptoms, treatment, prevention/screening, links to research articles, and ongoing clinical trials. An interactive tutorial provides some easy-to-understand background information and is designed to be especially accessible to those who are hearing or visually impaired. Prostate cancer information also is available on MedlinePlus' prostate cancer health topic page in Arabic, Chinese, French, Japanese, Korean, Russian, Somali, Ukrainian, Vietnamese, and Spanish. The links to prostate cancer information in international languages is on the upper right side of the page.

To find MedlinePlus' prostate cancer health page, type 'prostate cancer' in the search box on's home page. Then, click on 'Prostate cancer (National Library of Medicine).

Finally, the current study is a reminder that clinical trials exist to find out what works. While two promising, inexpensive supplements were ineffective deterrents to prostate cancer, an effort remains to discover some basic science questions about prostate cancer's development. As more research about prostate cancer's underlying basic science, prevention, diagnosis, screening, treatment, and management occurs, we invite you to stay informed by using

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