B Vitamins Neither Harm nor Help Colorectal Cancer Risk
Taking a combination of three B vitamin supplements, including folic acid, appears to neither increase nor decrease the risk of colorectal adenomas or polyps, which have the potential to become cancerous, at least among women at high risk for heart disease, according to a new study. The study was published in the Journal of the National Cancer Institute.
In the study, approximately 5,500 women were randomly given a daily B vitamin supplement or placebo. The supplement was made up of folic acid (B9), vitamin B6 and vitamin B12. Folic acid is the synthetic form of folate, a vitamin found in dark leafy greens and peanuts. Neither the participants, who were part of a cardiovascular study, nor the researchers knew who was taking what.
After over seven years of taking the daily supplement and another two years of follow-up, the researchers found no difference in colorectal adenomas between the women taking the B vitamins and the placebo group. Colorectal adenomas or polyps are linked to increased risk of colorectal cancer. The finding held when the researchers took into account alcohol intake, history of cancer, body fat, and other factors that affect risk.
This study adds to a relatively large body of research on colorectal cancer and B vitamins, specifically folic acid, that has led to dual findings. Earlier animal studies and – and some population studies – suggested folate and B vitamins may reduce colorectal cancer risk, but the studies are overall inconsistent. But ecologic observational studies have reported an increase in colorectal cancer incidence in the years after foods were fortified with folic acid.
There are no studies that link foods containing folate with increased cancer risk; folate-containing foods include spinach, peanuts, and beans, which all contain numerous cancer-protective compounds.
Source: Yiqing Song et al. “Effect of Combined Folic Acid, Vitamin B6, and Vitamin B12 on Colorectal Adenoma.” J Natl Cancer Inst. First published online: October 12, 2012.