Folic acid plays an important role in normal fetal development. Folic acid supplements and the addition of folic acid to many foods have resulted in a significant drop in the incidence of nervous system malformations, including spina bifida. Supplementation with folic acid appears to have reduced the incidence by as much as 50%.

The value of folic acid outside of pregnancy is a bit more controversial. Folic acid supplements may be of some value in women at risk of vascular disease and to prevent some forms of cancer.

Some studies have shown a relationship between vascular disease and high blood levels of the amino acid homocysteine. Higher levels of blood homocysteine are possibly linked to an increased risk of heart attack and stroke.

Folic acid is one of the regulators of homocysteine levels in the blood. Folic acid supplementation can lower blood homocysteine levels. However, just lowering the homocysteine level with extra folic acid does not decrease the risk of heart attack or stroke.

Several studies have suggested that diets rich in folic acid may reduce the risk of certain cancers, including breast, cervical, pancreatic, lung, brain, and colon and rectum. Whether folic acid supplements do the same has not been proven.

Some studies show that women who ingest the highest amounts of folic acid in combination with a multivitamin have less risk of developing colon or rectal polyps and cancer than those who take in lower amounts of folic acid. This suggests that it may be the folic acid that reduces cancer risk, but the evidence is by no means conclusive. Additional studies are ongoing. It will be a number of years before we know the real answer.