Folic acid should be routinely added to bread flour in Britain to reduce the number of children born with defects such as spina bifida, food experts have ruled.

Members of the Food Standards Agency (FSA) board unanimously backed the measure today, after a long-running debate on the pros and cons of the mandatory fortification of flour.

A final decision will rest with Government.

Folic acid is a synthetic form of the B vitamin folate. There is evidence that mothers who take it at the time they get pregnant greatly reduce their likelihood of giving birth to a baby with a split in the protective, bony tube around the backbone, leaving the spinal cord unprotected and at risk of neurological damage.

The FSA already advises women to eat extra folic acid when trying to get pregnant, but this strategy has not succeeded because about half of pregnancies are unplanned.

Between 700 and 900 pregnancies per year in the UK are affected by neural tube defects (NTDs) such as spina bifida.

Mandatory fortification already happens in the United States, Canada and Chile, where it has cut NTD rates by between 27 per cent and 50 per cent. A similar success rate in Britain would prevent between 190 and 450 babies being born with spina bifida each year.

It will be introduced in Ireland next year and is under consideration in Australia and New Zealand.

One study has raised concerns that folic acid could mask the signs of vitamin B12 deficiency in elderly people, which can in severe cases lead to neurological damage. There is no evidence of this happening when folic acid intake was 1mg per day or less, however.

It is not known whether eating excessive amounts of folic acid might increase the risk of cancer.

Critics of mandatory fortification describe it as “mass medication” which will limit consumer choice. The FSA board was told that a “clear opt-out” should be available for shoppers who do not want extra folic acid.

The FSA board rejected the measure five years ago due to lack of available evidence about possible risks and benefits, but a panel of UK scientific experts last year came out in favour of mandatory fortification.

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