Do Folic Acid, B Vitamins Prevent Cancer—or Cause It?

Neither, a new study suggests

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The latest study of people taking folic acid and vitamin B supplements is either disappointing or reassuring, depending on how you look at it. Researchers set out hoping to show that these vitamins could prevent breast cancer—and perhaps other cancers—in women with less-than-ideal health. But they seem to have struck out, HealthDay reports.

On the other hand, recent research had raised the frightening possibility that folic acid accelerates the growth of malignant tumors, a subject I've explored in some detail. Experts theorize that folic acid, which is a crucial nutrient for pregnant women, might inhibit the development of new malignancies while paradoxically fostering the growth of cells that have already turned bad.

In that sense, the new study is reassuring. Researchers led by Shumin Zhang of Harvard Medical School found no sign of increased cancer risk in women who took folic acid and vitamins B6 and B12 for the duration of the trial, which followed each woman for up to 7.3 years. They reported their findings in the Journal of the American Medical Association.