Professor John Scott of Trinity College, Dublin, said the proven role of folic acid in pregnancy, and growing evidence that it protects against heart disease and bowel cancer, amount to a "convincing argument" for adding it to all flour.
He told a conference organised by the British Nutrition Foundation last week that the scientific benefits were not in doubt. The only question was whether high doses could be damaging to some people.
"It is incumbent on us to do something so long as it's safe," he said. "My personal view is that if it were added to flour in small amounts it would do some good and would certainly do no harm."
Professor Scott is a member of the Committee on Medical Aspects of Food Policy (Coma), a government advisory panel which has been examining the issue of folic acid fortification for more than a year. In the US, the Food and Drug Administration has ordered fortification of all flour and cereals since1998.
Folic acid, part of the vitamin B complex, is found in green, leafy vegetables. It has long been known that the levels in the diet are inadequate to prevent neural tube defects such as spina bifida, and supplements are routinely given to pregnant women.
Heart disease is known to be linked with high levels of homocysteine in the blood. A study in the New England Journal of Medicine last year showed that giving the supplements to people with heart disease lowered the blood levels of homocysteine, reducing their risk in the same way as lowering cholesterol does.
A US study by Walter Willetts published in Annals of Internal Medicine showed that people who took folic acid supplements for 15 years had a sharply reduced risk of bowel cancer compared with those who took it for five years.
Homocysteine has also been implicated in Alzheimer's disease. Researchers from Oxford University reported last year that people who died of the disease had high levels of the amino acid in their blood which may have triggered a "vascular event", interrupting the blood supply to the brain.
In Britain, many cereal manufacturers already add folic acid to products such as cornflakes. But making it compulsory would raise the dosage. Some Coma panel members fear that if fortification were made compulsory, the total dosage taken by individuals would be so high as to put them at risk, and thus raise the threat of litigation.
The main risk is to people with pernicious anaemia, a vitamin B12 deficiency which can cause damage to the nerves if it is not treated. Giving high levels of folic acid supplements to people with the condition could mask the symptoms, exposing them to misdiagnosis and opening the door to law suits.
Professor Scott said the argument among Coma's experts was finely balanced but it would report to ministers with a recommendation in the summer. The options are to make fortification compulsory, to leave it voluntary, or to reach an agreement with the flour millers to add it on the Government's recommendation. "The question is whether you can add enough [to flour] to get the benefit without getting into the problem [of masking pernicious anaemia]," the professor said. "We should definitely do good if we can but the medical axiom of doing no harm is important."Reuse content