Folic acid for the prevention of neural tube defects.

Abstract

The editorial by Mitchell welcomed the USPSTF recommendation that women of child-bearing age in USA should take a daily supplement containing 400-800 μg of folic acid to prevent neural tube defects (NTDs). But the rationale for the recommendation is puzzling. The recommendation makes sense for countries without mandatory folic acid fortification. However, as Mitchell says, two case-control studies in the USA after fortification have failed to show an additional benefit of folic acid supplementation in the prevention of NTDs. Mitchell suggests that folic acid fortification may be preventing nearly all cases of folic acid–related NTDs. Her suggestion is consistent with a ‘floor-effect’ for folate-sensitive NTD