A UK Department of Health committee has recommended the adding of folic acid to flour to reduce the level of neural tube defects (NTDs). Yet researchers writing in the British Medical Journal warn that caution is needed before introducing such a policy. For people with epilepsy, folic acid could lead to reductions in the levels of phenobarbitone, primidone and phenytoin.
NTDs are birth defects occurring in the brain or spinal cord and are amongst the most common of all serious birth defects. The neural tube is the part of the foetus that becomes the spinal cord and brain. The two major types of NTDs are anencephaly and spina bifida.
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 per cent 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?