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More bad news for antioxidant supplements. According to a study published today in the Journal of the American Medical Association, taking supplements of vitamins C and E doesn't prevent heart attacks or stroke.

And last month, after researchers from the Cleveland Clinic discovered that selenium and vitamin E pills did nothing to ward off prostate cancer - and may even increase risk of the disease - they instructed the study participants to stop taking their supplements.

These findings add to growing evidence that antioxidant supplements are worthless at fighting disease. A report published earlier this year concluded after analyzing 67 studies involving 232,550 participants that, over all, popping an antioxidant supplement did not reduce the risk of dying from any cause in healthy or sick people.Antioxidants such as vitamins C and E, selenium and beta carotene are thought to thwart damage caused by free radicals, highly reactive oxygen molecules that harm cells, boosting the risk of cancer and other diseases. Antioxidants are also thought to slow or prevent the buildup of fatty plaques in arteries by preventing damage to LDL cholesterol by free radicals.

Research has linked diets high in antioxidant-rich foods to a lower risk of heart attack and certain cancers. However, well-controlled studies using antioxidant supplements have not uncovered benefits.

In today's study, called the Physicians' Health Study II, researchers from Harvard University's medical school assigned 14,461 healthy men, aged 50 or older, to take either 400 international units (IU) of vitamin E every other day, 500 milligrams of vitamin C daily, or a placebo pill.

After eight years, neither supplement lowered the risk of cardiovascular disease. Compared with men taking the placebo, vitamin E and vitamin C users were just as likely to suffer a heart attack or stroke, or to die from heart disease.

This study also found a significantly higher risk of hemorrhagic stroke among vitamin E users. (A hemorrhagic stroke, which accounts for 20 per cent of stroke cases, is caused by a weakened blood vessel that ruptures and bleeds into the brain.) No harmful side effects were observed for vitamin C.

Findings from earlier studies that looked at preventing other cancers suggested that supplemental vitamin E and selenium guard against prostate cancer. A 1996 study of 1,312 adults with skin cancer who took a 200-microgram supplement of selenium daily for prevention of the disease showed that the men were 52 per cent less likely to be diagnosed with prostate cancer.

In 1998, a Finnish study of 29,133 male smokers who took 50 IU of vitamin E daily in the hopes of preventing lung cancer found 32 per cent fewer prostate cancers among vitamin E users.

In 2001, the selenium and vitamin E cancer prevention trial (known as Select) set out to substantiate these findings. The randomized controlled trial gave 35,000 men, aged 50 or older, either vitamin E (400 IU) and selenium (200 micrograms) together, vitamin E alone, selenium alone or a placebo.

Last month, early findings from Select dashed hopes raised by prior studies. On Oct. 28, participants were told to stop taking their pills after the data showed no benefit - vitamin E and selenium, taken alone or in combination, did not prevent prostate cancer.

The early analysis also revealed two worrisome trends: a small increase in the number of prostate cancers among vitamin E users and a small rise in Type 2 diabetes among those taking selenium. Neither finding was statistically significant, meaning it could be a coincidence. These trends were not observed among men taking vitamin E and selenium supplements together.

The Select investigators will continue to follow participants for three years to determine any long-term effects.

In both studies, synthetic vitamin E supplements were given. It's possible that other forms of vitamin E may have been more effective.

If you're left wondering what to do with your antioxidant supplements, it seems it's time to trade them in for a healthy diet - at least when it comes to preventing heart disease and prostate cancer. (Standard multivitamins containing antioxidants in low doses are considered safe provided you take only one a day, although they have not been proven to guard against cancer or heart disease.)

Studies conducted in people at low risk and high risk for heart disease provide no evidence that vitamin C or E supplements offer protection from heart attack or death from heart disease. Observational studies have, however, reported a lower risk of heart attack among people who consume foods naturally high in the vitamins.

Numerous studies have also linked a higher intake of selenium-rich foods to less prostate cancer, mainly in men with low blood levels of the mineral (i.e. men whose diets provide little selenium).

So far, antioxidant supplements appear to benefit only people with age-related macular degeneration (AMD), an eye disease that attacks the central part of the retina that controls fine, detailed vision. A supplement containing vitamin C, vitamin E, lutein and zinc has been shown to reduce the risk of advanced AMD and its associated vision loss.

My advice: Stick with a multivitamin, extra calcium if your diet doesn't provide enough and, of course, 1000 IU of vitamin D a day as recommended by the Canadian Cancer Society. Get your antioxidants from foods. Doing so means you're also consuming protective phytochemicals, fibre and other vitamins and minerals - all of which probably work together to combat disease.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.

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Antioxidants 101

TRISH McALASTER / THE GLOBE AND MAIL