Folic Acid, Vitamin B6, B12 Do Not Affect Cancer Risk
Previous studies have shown a connection between folate, B6 and B12 vitamin intake and cancer prevention. Approximately one-third of adults in the United States take a daily multi-vitamin containing these supplements. Now, researchers from Brigham and Women’s Hospital (BWH) have found no association between folic acid, vitamin B6 and B12 intake and overall cancer risk in middle aged women.
“Women have been under represented when it comes to clinical trials with B vitamins. This study shows that combined treatment of folic acid, vitamin B6 and B12 provided neither beneficial nor harmful effects on overall risk of cancer for women aged 42 years or older with underlying cardiovascular disease or risk factors,” said Shumin Zhang, MD, ScD, lead author of the study and a researcher in the Division of Preventive Medicine at BWH.
Researchers assigned 5,442 female health professionals aged 42 years or older to receive either a daily combination of folic acid, vitamin B6 and B12 or placebo starting April 1998 through July 2005, when the US food supply began to be fortified with folic acid. The women either had preexisting cardiovascular disease or carried three or more risk factors for coronary disease. Of the participants, 187 who received the daily supplement developed invasive cancer compared to 192 who received the placebo. Researchers found that treatment with combined folic acid, vitamin B6 and B12 has no effect on total invasive cancer, breast cancer or deaths from cancer. Researchers note that there was a reduced risk for total invasive cancer and breast cancer observed in women who were 65 or older when enrolled in the study and were randomized to receive the combination folic acid, vitamin B6 and B12, but they cautioned that these subgroup findings may have been due to chance.
“Despite the apparent lack of benefit from these supplements for cancer prevention, several studies suggest that dietary sources of folate, such as dark green leafy vegetables, may lower cancer risk. Also, previous studies have shown conclusively that folic acid lowers the risk of certain birth defects, such as spina bifida, and adequate intake is important throughout pregnancy,” said JoAnn Manson, MD, DrPH, senior author of the paper and chief of Preventive Medicine at BWH.