Neural tube defects are malformations in the fetus that occur during pregnancy. The defects involve the skull and spinal column. Researchers think that most Americans get between 220 and 280 mcg a day of folate from their diets. Women of childbearing age should also take 400 mcg of folic acid daily. This intake should be from fortified foods, supplements, or both.
Folic acid has no known toxic level.
However, daily intake of folic acid should not exceed 1,000 mcg. Too much folate can mask the symptoms of a vitamin B12 deficiency. The FDA restricts the amount of folic acid supplements to 400 mcg for adults. Supplements for pregnant women are restricted to 800 mcg. A neural tube defect occurs when the neural tube fails to close properly.