B Vitamin Supplements Don't Affect Colon Cancer Risk: Study
Findings are reassuring, experts say
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Friday, October 12, 2012
As many as 35 percent of Americans take supplements containing B vitamins, and millions consume folic acid in fortified cereals each day. Concerns had been raised, on the one hand, that B supplementation might increase the odds of precancerous lesions, while other research had suggested a cancer-protective effect.
This new study compared a vitamin B combo pill with an inactive placebo in more than 5,400 older women at high risk of cardiovascular disease and found the supplements had no significant effect on the risk of colon cancer.
"The study's findings are reassuring, because there has been a concern that folic acid supplements may promote colorectal adenoma growth," said Marji McCullough, strategic director of nutritional epidemiology at the American Cancer Society, who was not part of the study. Adenomas are a precursor to cancer.
For their research, the Harvard Medical School team led by Dr. Yiqing Song used data from the Women's Antioxidant and Folic Acid Cardiovascular Study. Median age of the women was 62 at the study's start. Those on the vitamin-B regimen received a high dose -- 2.5 milligrams -- of folic acid (the synthetic form of folate), 50 mg of vitamin B6 and 1 mg of B12 daily.
Among these women, Song's group zeroed in on more than 1,400 who underwent an endoscopic exam sometime during the study's nine year follow-up period.
The report was published in the Oct. 12 issue of the Journal of the National Cancer Institute.
The author of an editorial accompanying the study, Regina Ziegler, from the division of cancer epidemiology and genetics at the U.S. National Cancer Institute, pointed out that "this randomized trial, along with other trials, does not suggest that high doses of folic acid are a promising chemoprotective agent for colorectal cancer."
Nor does high-dose folic acid appear to increase the risk of colorectal cancer, said Ziegler. "This is reassuring," she added.
Many foods in the United States are fortified with folic acid to help prevent birth defects known as neural-tube defects. Some experts feared the increased consumption of folic acid could raise the risk of colon cancer, Ziegler explained.
Duffy MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, agreed that there's "some good news" in this report.
"In the era of folic acid fortification, adding a B vitamin supplement does not predispose you to colon cancer," he said. "Now we have a randomized trial to verify the safety of folic acid supplementation."
McCullough, meanwhile, said the American Cancer Society prefers lifestyle modification rather than vitamin supplements for thwarting cancer.
"The American Cancer Society does not recommend taking dietary supplements for cancer prevention," she said.
"We do know you can lower your risk of colorectal cancer by limiting red and processed meat intake, eating fruits and vegetables (naturally rich in folate), being physically active, avoiding obesity and, if you are over 50, getting colorectal cancer screening," McCullough said.
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