The evidence that neural tube defects may be caused by relatively low levels of serum folic acid have led to a policy that women before and in early pregnancy should take supplements of folic acid in order to reach intake levels of at least 400mg of folic acid per day. This level of recommendation has started several research programmes with the question whether adequate folic acid levels in the blood could also be obtain by specific dietary and food recommendations in stead of taking folic acid tablets or fortification of foods with folic acid.