High doses of folic acid may cause abdominal cramps, diarrhea, rash, sleep disorders, irritability, confusion, excitability, behavioral changes and seizures, according to WebMD. Some research suggests that taking folic acid at doses of 800 to 1200 micrograms may increase the risk of heart attack in people with heart disease.
Other research suggests that high doses of folic acid may increase the risk of prostate or lung cancer, notes WebMD. Unless told otherwise by a physician, patients should not take more than 400 micrograms of folic acid per day.
Deficiency of folic acid can cause anemia, states Web MD. Doctors advise women who are pregnant or wanting to become pregnant to take folic acid to prevent birth defects in their babies. Folic acid reduces levels of homocysteine in people with serious kidney disease. Because high levels of homocysteine are linked to heart attack and stroke, doctors recommend people with elevated homocysteine levels take folic acid. Some people also take folic acid to prevent colon cancer and cervical cancer. Folic acid is useful for memory loss, Alzheimer's disease, age-related hearing loss and age-related eye disease.
Folic acid is a water-soluble B vitamin, explains WebMD. Leafy vegetables, fruits, mushrooms, beef liver and kidney, orange juice and tomato juice are rich in folic acid.