Prospects for prevention of neural tube defects by vitamin supplementation.

Recent studies have resolved the debate over the role of vitamins in preventing neural tube defects. The British Medical Research Council trial demonstrated that 4 mg of folate daily, but not other vitamins, prevented 72% of recurrences. The Hungarian trial prevented neural tube defects in women who had not previously had affected children by giving multivitamins containing 0.8 mg of folate. The US Public Health Service currently recommends that women at risk for becoming pregnant take 0.4 mg of folate daily. Unfortunately, most pregnancies are unplanned, and women not planning to become pregnant may not follow this recommendation. Therefore, the US Food and Drug Administration is exploring methods of food fortification. Because large doses of folate have been reported to ameliorate B12 deficiency anemia while allowing neurologic damage to progress, and to cause electroencephalogram abnormalities in epileptics, it is important to plan fortification carefully and to monitor both toxicity and benefits.