High dose vitamin E supplements may raise risk of prostate cancer: Study

By Dr. Ananya Mandal, MDOct 13 2011

A new large study reveals that high doses of vitamin E can significantly increase the risk of men developing prostate cancer.

The chances of developing the disease rose by 17 per cent, even years after men stopped taking the vitamin, claim researchers. This comes right after the study which found women taking multivitamins and other supplements have an increased risk of dying.

The new findings ironically come from a U.S. trial which was attempting to confirm earlier reports that extra vitamin E and the mineral selenium could help prevent prostate cancer. Researchers found more cases of prostate cancer among men taking 400 international units (IU) of vitamin E a day than placebo, or dummy capsules. This is the equivalent of 363mg a day – the measurement used in Britain – which is 30 times more than the recommended daily amount.

Lead researcher Dr Eric Klein, a urologist of the Cleveland Clinic in Chicago, said millions of older Americans take supplements containing vitamin E, many of them at the megadose levels of the study.

Writing in the Journal of the American Medical Association, he said, “The observed 17 per cent increase in prostate cancer incidence demonstrates the potential for seemingly innocuous yet biologically active substances such as vitamins to do harm…The lack of benefit from dietary supplementation with vitamin E or other agents with respect to preventing common health conditions and cancers or improving overall survival, and their potential harm, underscore the need for consumers to be skeptical of health claims of unregulated over-the-counter products in the absence of strong evidence of benefit demonstrated in clinical trials.”

More than 35,000 healthy men in their 50s and older took part in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) at 427 centers in the US, Canada and Puerto Rico. They were given either a daily placebo or various combinations of vitamin E and selenium supplements between August 2001 and June 2004.

In 2008, volunteers were told to stop taking the supplements because the trial was not going to achieve an expected 25 per cent reduction in prostate cancer risk. The researchers continued monitoring the health of some men, which is when more cases of prostate cancer emerged in the group assigned to take vitamin E.

A total of 529 men given placebo pills developed prostate cancer compared with 620 taking vitamin E alone, 575 taking selenium alone, and 555 taking both supplements. Although selenium alone, and selenium plus vitamin E, were associated with slightly raised prostate cancer rates, they were not statistically significant. But the researchers said the extra risk associated with vitamin E became apparent during the third year of the trial and could not have occurred by chance.

But co-author Dr Lori Minasian, acting director of the US National Cancer Institute, said it was a biological ‘mystery’ why taking vitamin E should result in an extra risk of prostate cancer. Dr Helen Rippon, head of research management at The Prostate Cancer Charity, said, “This new large-scale research radically challenges the hope that vitamin E and selenium supplements might be an effective way for men to reduce their risk of developing prostate cancer…Rather, the researchers have shown that, far from being protective, selenium has no effect upon prostate cancer rates in men, whilst  excessive levels of vitamin E actually increases a man’s risk of getting the disease considerably. “ She added, “Dietary supplements are often taken without the advice of medical professionals as they are often seen as risk free – but as this important new study shows, the true effects of these supplements are not always clear…Unfortunately for men, this means that a simple dietary supplement to protect against prostate cancer remains elusive. Therefore, any man wishing to reduce their risk of the disease should stick to a healthy, balanced diet which will ensure they get the right level of vitamins and minerals they need, without supplements.”

In the UK, the recommended daily amount of vitamin E is 12mg and most multivitamin pills contain between 15mg and 30mg. However, the UK Expert Group on Vitamins and Minerals says the upper ‘safe’ limit is between 700 and 800mg a day – twice as much as taken in the study.

Dr Carrie Ruxton from the industry-backed Health Supplements Information Service, said the study volunteers were taking extremely high doses that would be regularly taken by few Britons.

She said, “This is yet another trial, of which there have been many during recent years, in which very high dose dietary supplements are used in an attempt to prevent disease…Yet, vitamins and minerals are not intended for this purpose; they are essential nutrients which should be consumed in recommended amounts to maintain health and prevent nutrient deficiency.”

Because the government rules for the sales of vitamins and supplements are so much more lax than those for pharmaceuticals, you can still walk into a health food store today and find a bottle of Vitamin E with a label that reads: “Supports prostate health.” “Consumers should be skeptical about claims that are made on bottles and elsewhere unless there is solid scientific evidence,” Klein says. “If you have enough of these vitamins in your system, extra doesn't help you any, and too much of something like this can be harmful,” said Dr. Klein. Experts unanimously advise to eat more fresh fruits and vegetables instead of relying upon supplements.