Why do people take folic acid?

Folic acid supplements are standard for pregnant women and women who plan to become pregnant. Folic acid can lower the risk of preeclampsia and early labor. Folic acid also reduces the risk for devastating birth defects of a baby’s brain and spine -- spina bifida and anencephaly -- by 50% to 70%.
Many doctors recommend that any woman of childbearing age take either a multivitamin or folic acid supplements. Folic acid can protect against birth defects that may occur before a woman knows she is pregnant.
Folic acid is used to treat deficiencies, which can cause certain types of anemia and other problems. Folate deficiencies are more common in people who have digestive problems, kidney or liver disease, or who abuse alcohol. When used to treat deficiencies, folic acid should be used along with vitamin B12. In addition to treating anemia, they work together to promote neurological health. Folic acid is also used to reduce the toxicity of the drug methotrexate in psoriasis and rheumatoid arthritis patients.