"After nearly 10 years of supplementation with either vitamin E or vitamin C, we found no evidence supporting the use of either supplement in the prevention of cancer," said Howard D. Sesso, Sc.D., M.P.H., an assistant professor of medicine at Brigham and Women's Hospital. "While vitamin E and C supplement use did not produce any protective benefits, they also did not cause any harm," he added.
The research, funded by the National Institutes of Health and several vitamin makers, tracked cancer risk in 14,641 male U.S. doctors who took either 400 IU of vitamin E every other day or a placebo, or 500 milligrams of vitamin C daily or a placebo. Their average age was 64 at the start of the study and they were followed for eight years on average.
The participants experienced a total of 1,929 cases of cancer, including 1,013 prostate cancers. Overall, 490 men taking vitamin E developed prostate cancer compared to 523 in the placebo group. Similar results were seen for vitamin C. The overall risk of cancer generally was also not statistically significant between the two groups.
"Well-conducted clinical trials such as this are rapidly closing the door on the hope that common vitamin supplements may protect against cancer," said Marji McCullough, nutrition chief at the American Cancer Society. "It's still possible that some benefit exists for subgroups that couldn't be measured, but the overall results are certainly discouraging."
The public has been whipsawed by good and bad news about vitamins. Previous laboratory research and observational studies in which people who reported eating a diet rich in vitamins E and C were found to have a lower risk of cancer, had suggested that taking these vitamins as individual supplements may offer some protective benefits.
"The American Cancer Society recommends getting these and other nutrients by eating a mostly plant-based diet with a variety of vegetables, fruits and whole grains. A bonus is that this type of diet helps to prevent obesity, which increases the risk of several cancers," said McCullough.
VietNamNet/Xinhuanet
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