A UK Department of Health committee has now recommended universal fortification of flour with folic acid to reduce the level of neural tube defects. Yet researchers in this week's BMJ warn that we need to be cautious before introducing such a policy.
Although the benefits of supplementation are clear, the possible harms of such a policy are not, as there is no trial evidence of the efficacy and safety of the intervention, write child health experts, Brian Wharton and Ian Booth.
In the United States, a 19% reduction in the prevalence of neural tube defects has been reported following folic acid fortification of grain products. However, this reduction is less than half that seen in England and Wales in the 1980s without a fortification programme. These data are hardly a substitute for a controlled field trial, they argue.
Furthermore, mandatory and universal fortification does not, at present, need the same trial evidence as for a drug. Yet a drug is not given in imprecise doses to all members of the population without choice or indication, they add.
In 1998, 399 pregnancies in England and Wales were affected by central nervous system malformation. Although a field trial would not be easy, say the authors, is it acceptable to increase the folic acid intake of 50 million people to prevent a third to two thirds of these affected pregnancies before there is firm evidence of efficacy and safety in people who are not pregnant?