B vitamins might not cut cancer risk
WASHINGTON - Vitamin B supplements do not appear to protect against cancer as some previous research had suggested, according to a US study published yesterday.
Women who took a daily supplement that included vitamins B-6 and B-12 and folic acid, also known as vitamin B-9, for about 7 1/2 years were no more or less likely to develop or die from cancer than women who took a placebo, the researchers said.
"This study shows that supplementation with the combined B vitamins provided no beneficial effect and no harmful effect. So in terms of cancer risk, this may not be an effective approach," said Dr. Shumin Zhang of Brigham and Women's Hospital and Harvard Medical School, who led the study.
The study, published in the Journal of the American Medical Association, involved 5,442 female healthcare professionals from across the United States. Their average age was 63.
The women had cardiovascular disease or risk factors for it such as high blood pressure or high cholesterol levels.
Some researchers had been hopeful that B vitamins might protect against cancer after earlier studies indicated that people who get more of these vitamins may have a lower risk of developing cancer, especially colon cancer.
But in the new study, the number of women who developed cancer was nearly identical in the vitamin supplement group (187 women) and the placebo group (192 women). The two groups had similar risks for developing any type of cancer or dying from any type of cancer.
The study did find that among women 65 and older, those getting the daily B vitamins were 25 percent less likely to develop any type of cancer and 38 percent less likely to get breast cancer. But Zhang said it is not clear whether this is a chance result.
People can get folic acid and other B vitamins in the diet through leafy green vegetables and fortified cereals or through vitamin supplements.
B vitamins are essential nutrients for growth, development, and other functions. For example, folic acid is important in the production of red blood cells and is important for women to prevent certain birth defects.
Despite this study's findings, other research suggests that people who eat foods high in folic acid may lower their cancer risk, according to Dr. JoAnn Manson of Brigham and Women's Hospital, who also took part in the study.