The recommendation by the Food Standards Agency to add the vitamin folic acid to all flour and bread on sale in Britain within the next year is one of the most sensible steps ever taken to bolster this nation’s public health. Research in Britain, Canada and the US has clearly shown the importance of folic acid in preventing babies being born with spina bifida and brain defects. Doctors have known for years that women who have taken the vitamin since the start of their pregnancy can avoid the terrible defects that blight the lives of up to 200 spina bifida children born each year. They now believe that folic acid may also combat strokes, bone disorders and heart disease in the whole population.

Formal recommendation has been a long time coming. Nutritionists first suggested the addition of folic acid ten years ago. In 2003 the food watchdog rejected the move, by only one vote, because of worries that the fortification of food would mask cases of vitamin B12 deficiency among the elderly. Those worries have proved largely unfounded. And so tomorrow the Food Standards Agency board will recommend in principle that all brown and white flour be fortified with folic acid.

This marks the first time since the Second World War that manufacturers have been ordered to add nutrients to food on the ground of public health. The decision is nevertheless certain to stir controversy. The objections will be on two counts: first, that whatever the scientific evidence, there can be no absolute certainty that the addition of folic acid is without any negative side-effects; and secondly, that the Government has no right to impose mass medication on the population.

Instead, objectors say, the Government should allow a free choice, and, if it is convinced of the value of folic acid, launch an information and education campaign to persuade women to take it. Such an argument is wholly spurious. No information campaign reaches everyone. There is always a stubborn 20 per cent of the population immune to press or television persuasion and with little care for their own health or that of their unborn children. This is a classic public health issue. Cholera would never have been conquered if clean water had been optional, or road accidents reduced if seat belts were not compulsory.

Protesters will point to the analogy with fluoride, which still has not been introduced everywhere despite its efficacy in reducing tooth decay. The circumstances are slightly different: fluoride, in many places, is found naturally in water, and its addition is not always necessary. Folic acid, however, needs to be added. Already calcium, iron, thiamine and niacin are compulsory ingredients in white or brown flour. This raises the issue of “organic” food — and wholemeal bread is exempt from the regulations. An opt-out could also be made for folic acid — hardly the best option, but one that might satisfy fundamentalist libertarians. What is important, however, is that the best scientific evidence has been sifted and acted on. There could be no more welcome example of public health policy in action.