Introduction

The principal rationale for medical research is to improve health. In clinical medicine, the goal is to get the results of medical research to individual patients as soon as possible. In preventive medicine, however, the challenge is to apply clinical and epidemiological evidence to whole populations. The most effective way to do this is through government legislation. However, once a government requires an intervention, individuals may have little chance to influence whether they are exposed to it. This means that government decisions to require prevention measures are political. Unless the decision is anchored securely in science, even weak political arguments can over-rule the science and the needs of public health. We consider the challenges that face the introduction and maintenance of evidence based public health interventions using the current debates over preventing birth defects by fortification of flour with folic acid and the safety of the MMR (measles, mumps, and rubella) vaccine.1 2

Fortification of cereal grains with folic acid

Two randomised controlled trials and data from controlled observational studies provide a strong scientific basis for the consensus that synthetic folic acid can prevent spina bifida and anencephaly.3 4 The main ways to get synthetic folic acid are from fortified food or vitamin pills. Some countries have chosen to rely on vitamin pills and others have fortified flour and other cereal grain products.

The United Kingdom and Netherlands have attempted to protect the population fully through health education programmes. In both countries, most people do not consume vitamin pills. The education programmes have increased the number of pregnant women who take folic acid pills before pregnancy to about 50%, but they provide no protection for the 50% who do not take folic acid.5 6 Dependence on individual …