Folic acid and the prevention of neural tube defects

BMJ 1995; 310 doi: http://dx.doi.org/10.1136/bmj.310.6986.1019 (Published 22 April 1995) Cite this as: BMJ 1995;310:1019
  1. Nicholas J Wald,
  2. Carol Bower
  1. Professor Visiting research fellow Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, Medical College of St Bartholomew's Hospital, London EC1M 6BQ

    A population strategy is needed

    Over three years have passed since an increase in the intake of folic acid among women planning a pregnancy was shown to prevent most neural tube defects.1 The evidence is conclusive; prevention is effective for women who have not had a pregnancy in which the fetus had a neural tube defect as well as for those who have.2 National authorities have recommended that women planning a pregnancy should increase their intake of folic acid.3 4 5 The extra folic acid needed for a reasonable protective effect is 0.4 mg a day, twice the current average dietary intake of 0.2 mg. If no screening was carried out for neural tube defects (with subsequent abortions) about 1500 affected children would be born each year in Britain. Over 1000 of these defects could be prevented by women consuming extra folic acid. Sadly, most people are still not aware of the importance of folic acid in the prevention of neural tube defects.6 7 A public health initiative is urgently needed; the tragedy of a pregnancy in which the fetus has a neural tube defect is even greater when it can be so easily prevented.

    Some people argue that preventive strategies should be selectively targeted at women planning a pregnancy—on the grounds that only pregnant women and their children stand to benefit and only a few of these are affected. From a public health perspective, however, most disorders affect only a minority of people at risk and are often restricted to specific groups of the population (for example, children, pregnant women, or elderly people).

    Immunisation programmes apply to all even though only a small fraction of the population is likely to benefit. The prevention of rubella in pregnancy to avoid the congenital rubella syndrome originally focused on two target groups—teenage girls, who were vaccinated at school, and pregnant women, who were screened and, if found to be susceptible, vaccinated after their pregnancy. This selective approach had only a partial effect. Aiming at vaccinating 10-14 year old girls kept a pool of infection among men and boys and younger girls. Vaccination against rubella is now offered to all, boys included. The population approach of collective action has been an essential part of most of the achievements in public health. This is the strategy needed to prevent neural tube defects.

    Critics ask why some people should make changes to their lifestyle or diet that will benefit only others. Such an argument implies that we act selfishly and accept policies only if each of us benefits personally. Yet most people fall into at least one minority group. We take actions that can benefit others—and others take actions that can benefit us—provided that the risk to subgroups who might be harmed is minimal (or can be avoided by other means). If the only preventive measures introduced were those in which every individual to whom they were applied stood to gain we would have few preventive measures in place.

    A selective public health strategy to prevent neural tube defects would require women planning a pregnancy to take extra folic acid; this is less likely to be successful than a population approach. The women would have to take capsules: trebling the dietary intake of folic acid would require changes unlikely to be achievable in practice with currently available foods. A woman would have to consume over eight glasses of orange juice, 10 servings of broccoli, three servings of brussel sprouts, or appropriate combinations of such foods to receive an extra 0.4 mg of folic acid each day.

    Furthermore, a selective policy would fail to prevent neural tube defects in unplanned pregnancies. The population strategy avoids the problems of the selective approach, and since the remedy—the consumption of extra folic acid—is simple and cheap the mass of people who do not benefit directly need be no cause for concern.8 Folate deficiency occurs in groups other than pregnant women, so the population approach offers the potential for wider benefits. The crucial point is that even in large doses folic acid has not been shown to cause harm.9 Concern has been voiced about two groups. Folic acid may prevent the anaemia of pernicious anaemia and so alter the presentation of the disease, but this problem can be resolved by educating doctors that macrocytic anaemia does not inevitably accompany the neuropathy.8 Folic acid may also counter the anticonvulsant activity of some drugs used in epilepsy; the effect of fortifying food would probably be negligible but higher doses of anticonvulsant drugs might be needed for some patients.

    The solution, then, is to fortify food with folic acid. A staple food consumed in reasonably predictable quantities by almost everyone in the population needs to be chosen. It should then be possible to titrate the amount of folic acid added to achieve an extra average intake of 0.4 mg folic acid in the population without many people getting too much or too little. Cereal grain flour (including wheat flour and corn flour) is a convenient choice. The United States Public Health Service supports this proposal, and a United Kingdom Expert Advisory Group recommended the wide fortification of bread with folic acid.

    Unfortunately, a voluntary system of fortifying food with folic acid leaves the initiative with the food manufacturers, who do not see themselves as the custodians of public health. Manufacturers respond to what the public wishes to buy. The general public, however, cannot be expected to have sufficient detailed knowledge of the nutrients in foods for particular groups of people to select specific foods to avoid particular diseases at particular times in their lives. The public may reasonably expect that such nutritional issues will be covered by a national dietary policy.

    We believe that the rather loose voluntary recommendation on the fortification of bread should be strengthened into a compulsory policy; at the same time we think that the opportunity should be taken to select flour rather than bread for fortification. The fortification of flour at milling sites would be simpler and more economical than the fortification of bread at the much larger number of manufacturing sites.

    Some people will wish to buy unfortified foods, and unfortified flour should continue to be available—as should bread made with unfortified flour. These unfortified products would be the exception and would require special labelling. Fortified flour or bread should be the norm and freedom of choice would be preserved.

    White flour is already compulsorily fortified in Britain with two vitamins (niacin and thiamine) and two minerals (calcium and iron). The government is currently seeking opinions on revising the policy on fortification. It is suggesting that flour should be deregulated and that niacin and thiamine should no longer be added; this proposal is based on the absence in Britain of disease due to a lack of these two vitamins. The request for advice on this proposal provides public health professionals with an opportunity to recommend to the government the compulsory fortification of flour with folic acid. If this were done at a level that would increase average intakes by 0.4 mg a day most of the 1500 or so neural tube defects each year could be prevented. If this opportunity is missed the costs—the needless suffering of seriously disabled children, unnecessary terminations of pregnancy carried out because of an antenatal diagnosis of a neural tube defect, and wasted financial resources—will be great.


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