Researchers at the U.S. National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health,found that 0.4 milligrams (mg) a day of folic acid reduced by one third the baby's risk of isolated cleft lip (with or without cleft palate).

    Folic acid is a B vitamin found in leafy vegetables, citrus fruits, beans, and whole grains. It can also be taken as a vitamin supplement, and it is added to flour and other fortified foods. The recommended daily dietary allowance for folate for adults is 400 micrograms or 0.4 mg.

    "These findings provide further evidence of the benefits of folic acid for women," said Allen J. Wilcox, M.D. Ph.D., lead NIEHS author on the new study published online in the British Medical Journal.

    "We already know that folic acid reduces the risk of neural tube defects, including spina bifida. Our research suggests that folic acid also helps prevent facial clefts, another common birth defect." In the United States, about one in every 750 babies is born with cleft lip and/or palate.

    "Folic acid deficiency causes facial clefts in laboratory animals, so we had a good reason to focus on folic acid in our clefts study," said Wilcox. "It was one of our main hypotheses."

    This population-based study was conducted in Norway, which has one of the highest rates of facial clefts in Europe. The researchers examined the association between facial clefts and mothers' intake of folic acid supplements, multivitamins, and folates in diet.

    The researchers found that folic acid supplementation of 400 micrograms or more per day reduced the risk of isolated cleft lip with or without cleft palate by one-third, but had no apparent effect on the risk of cleft palate alone.