Neurotoxicity of Folic Acid

The present review summarises the neurotoxicological effects of folic acid. Some studies in animals have shown that folic acid is neurotoxic and epileptogenic when applied directly to the brain. One poorly controlled and not further reproduced study from 1970 reported neurotoxic symptoms like malaise, sleep disturbances, and mental changes in 14 healthy volunteers who took daily 15 mg of folic acid for one month. Five years later seizures were reported in a patient with poorly controlled epilepsy after high intravenous doses of folic acid. There are no further data that indicate that oral folic acid is directly neurotoxic in humans. Clinical studies, where daily doses of 5 to 15 for up to 3 years were applied, did not shown any evidence of folate associated neurotoxicity. It is outlined that rather a deficiency in folic acid, that induces a decrease in the synthesis of S-adenosyl-homocysteine and accumulation of homocysteine, may lead to neurotoxicological damage