Folic acid should be routinely added to flour to reduce birth defects such as spina bifida, the UK's official food watchdog said yesterday.
The Food Standards Agency (FSA) recommends the mandatory fortification of white and brown wheat flour.
Its support - included in papers published today - will be put to the FSA's board, which in turn will decide whether to recommend the measure to the Government.
Adding folic acid to bread via white and brown wheat flour would help cut neural tube defects (NTDs), according to scientific research.
Up to 900 pregnancies in the UK each year are affected by spina bifida and other NTDs.
The FSA's recommendations follow a long-running debate about the pros and cons of routinely adding folic acid - a synthetic form of the B vitamin folate - to flour.
In its board papers, the watchdog sets out its support for mandatory fortification.
If the measure is taken up, the FSA wants products containing folic acid at "nutritionally significant" levels to say so on labels.
New controls would be needed on the voluntary addition of folic acid to breakfast cereals and low-fat spreads and on the use of folic acid supplements, the FSA said.
The watchdog also wants monitoring for possible risks such as cancer to be brought in.
"The incidence of NTD-affected pregnancies in the UK is likely to be reduced if mandatory fortification of wheat flour with folic acid is introduced," the board papers say.
Wholemeal flour would be exempt from fortification in order to give consumers more choice.
Between 700 and 900 pregnancies are affected by NTDs every year, with most diagnosed women opting for abortions.
The FSA already advises women to eat extra folic acid when trying to get pregnant. But this strategy isn't effective because around half of pregnancies are unplanned.
Mandatory fortification has already been introduced in the USA, Canada and Chile, where it cut NTD rates by between 27% and 50%.
A panel of UK scientific experts last year came out in favour of mandatory fortification.
The Scientific Advisory Committee on Nutrition (SACN) said the measure should be brought in alongside controls on voluntary fortification, advice on the use of supplements, and long-term monitoring.
An FSA consultation on the issue drew 202 responses from industry, consumer groups and individuals.
The baking industry raised "practical concerns" about the fortification of bread. It said bread-making flour couldn't easily be separated from other flours in mills.
Previous studies have raised concerns that folic acid masks signs of vitamin B12 deficiency in the elderly, which in severe cases can cause neurological damage.
But the SACN's report, released in December, found no evidence of this happening when folic acid doses were 1mg per day or less.
The FSA board will reach a decision on the issue at its meeting in Nottingham on Thursday.
If it backs mandatory fortification, it will recommend the move to health ministers who will have the final say.