Why didn't the supplements prevent cancer, as some earlier research had suggested? One theory, Lin said, is that they might be effective in people who are poorly nourished, but not in well-nourished people such as the women in the study. She said some research has shown that diets lacking in antioxidants -- found in fruits and vegetables -- can lead to higher cancer rates.
The study isn't the final word, Lin said. "More studies need to be done to see who may benefit from antioxidant supplements. One trial study has suggested that men, compared with women, were more likely to gain benefits from supplementation with antioxidants in reducing cancer risk. However, such findings need verification."
Dr. Demetrius Albanes, senior investigator with the U.S. National Cancer Institute, who wrote a commentary accompanying the study, acknowledged that while the study results were disappointing, it's possible that the supplements could have had positive effects in women who weren't at high risk for cardiovascular disease, as were those in the study.
He added that the study indicated that vitamin E may have some benefit at preventing colon cancer specifically, as other research has suggested.
In the big picture, Albanes said, research shows that lower-calorie diets with plenty of fruits and vegetables do have benefits. "But right now, the issue of vitamin supplementation is still very much up in the air for men and for women," he added.
Learn more about the links between diet, exercise and cancer risk from the American Cancer Society.
SOURCES: Jennifer Lin, Ph.D., assistant professor of medicine, Brigham and Women's Hospital and Harvard Medical School, Boston; Demetrius Albanes, M.D., seni
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