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Supplements May Not Cut Cancer Risk
Dec. 30, 2008 -- For the second time in two months, new research shows no signs of cancer prevention from taking certain vitamin supplements.
In November, scientists noted no cancer benefits in male doctors assigned to take vitamin C or vitamin E pills. Now, other researchers report similar results in women at high risk of heart disease who took vitamin C, vitamin E, and beta-carotene supplements.
The new study "provides little or no evidence that such vitamin supplementation as tested offers any measurable preventive impact on cancer in women," states an editorial published with the study in the Jan. 7, 2009, edition of the Journal of the National Cancer Institute.
But the study tested a narrow question and isn't the final word, according to a spokesperson for the supplements industry.
Supplements Study
The new study comes from researchers including Jennifer Lin, PhD, of the division of preventive medicine at Harvard Medical School and Brigham and Women's Hospital in Boston.
Lin's team reviewed data on 7,600 U.S. women aged 40 and older who were followed for about nine years, on average.
When the study started, the women were 60 years old, on average. They had no history of cancer other than nonmelanoma skin cancer, but they were at high risk for heart disease because they had cardiovascular risk factors such as high blood pressure (hypertension), diabetes, obesity, or parental history of heart attack.
The women were randomly assigned to take vitamin C (500 milligrams of ascorbic acid) or a placebo daily, vitamin E (600 international units of alpha-tocopherol) or a placebo every other day, and beta-carotene (50 milligrams) or a placebo every other day.
Study's Findings
During the follow-up period, 624 women were diagnosed with cancer other than nonmelanoma skin cancer, and 176 women died of cancer.
The odds of being diagnosed with cancer or dying of cancer were similar between women taking the supplements or the placebo pills. So the researchers conclude that there was no overall advantage in taking the supplements individually or together, at least in women at high risk of heart disease.
Lin's team notes that their study was one of few trials that lasted a long time, but that cancer can take decades to develop, so the study may still have been too short to gauge the supplements' effects.
The study was only on vitamin C, vitamin E, and beta-carotene in supplements. The researchers didn't study those nutrients in food.
Supplement Industry's View
Lin's study was "well-conducted," but it's just one piece of a larger puzzle, says Andrew Shao, PhD, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a trade group for the supplements industry.
Shao points out that the women had adequate dietary intake of the antioxidants even without the supplements, so there wasn't a good comparison group of people lacking those nutrients.
It's "hard to say" whether the study lasted long enough, says Shao. He also notes the study's narrow focus on women at high risk for heart disease who began taking supplements at the average age of 60.
Shao doesn't claim that supplements, by themselves, prevent cancer. "These are nutrients. They're not drugs; they're not a magic bullet," says Shao. He says supplements are "just one tool," that, along with other healthy habits, "people should incorporate into their lifestyle to maintain health and avoid chronic disease."
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