Many Americans have begun taking folic acid supplements thinking that it can protect against colon cancer and also cut a person's risk of stroke and heart disease.
In the past, animal studies led researchers to believe that folic acid had these beneficial effects. The National Institutes of Heath funded a clinical trial that enrolled more than 1,000 men and women who previously had polyps removed from their colons.
Those in the study were randomly assigned to take daily pills containing either 1 milligram of folic acid or a placebo. The study showed that those who took the folic acid got just as many new colon polyps as those who took the placebo pills.
Robert Sandler, M.D., chief of the division of gastroenterology and hematology, told WebMD, "We are disappointed and surprised that it didn't work. In fact, there was some evidence that folic acid increased cancer risk."
Besides preventing birth defects in the brain and spine and other congenital abnormalities, the folic acid found in prenatal multivitamins has now been shown to prevent cancer in children whose mothers take the vitamins during pregnancy.
