The public is set to be asked if folic acid should be added to some types of flour to cut the risk of birth defects.
Folic acid might be added to white bread
A meeting of the Food Standards Agency this week is likely to sanction a 12-week consultation exercise, alongside consumer research.
The FSA favours mandatory fortification, but will await the results of the consultation before making a recommendation to ministers.
Folic acid cuts the risk of neural tube defects such as spina bifida.
However, there is concern that adding the vitamin to popular foods could be harmful to some elderly patients, as it could mask a deficiency in another B group vitamin - B12.
B12 deficiency is particularly common among the elderly - up to 10% of those aged 65 and older have borderline B12 levels and could tip into deficiency.
In extreme cases, this can cause irreversible damage to the nervous system, called subacute combined degeneration of the cord.
Last November the Scientific Advisory Committee on Nutrition (SACN) recommended the overall benefits of increasing people's folate levels would outweigh any risks.
Cuts the risk of neural tube defects, like spina bifida
Women recommended to take 400 microgram supplements when trying to get pregnant, and during first three months of pregnancy
Can mask an underlying vitamin B12 deficiency
May cut the risk of cardiovascular disease, and types of cancer
Some evidence it might raise the risk of pre-cancerous polyps in the bowel
The FSA favours adding folic acid to the nutrient mix already added to white flour.
However, under its draft proposals the vitamin would not be added to wholemeal products, or speciality breads.
Folic acid supplements (400 micrograms per day) are already recommended for women who are pregnant or planning a pregnancy.
However, research suggests that only half of women planning a pregnancy or who are pregnant adhere to this advice.
Also, as many as 50% of pregnancies are unplanned, meaning women may miss the opportunity.
Each year around 500-600 babies in the UK are reported to have neural tube defects. It is thought as many as 900 pregancies a year are affected, but many are aborted.
The SACN estimates that adding folic acid to flour could cut this rate in half.
It might also have a benefit in cutting heart disease, it said, although it is too early to tell for sure.
Research has shown that folate, of which folic acid is a form, which is found in certain foods cuts cardiovascular disease risk. Studies are ongoing to see if synthetic folic acid supplements do the same.
Data also shows that people other than women of childbearing age may be deficient in folate and might benefit from consuming higher levels.
Some foods in the UK, such as bread, breakfast cereals and margarine, already contain added folic acid.
Other countries, including the US, Canada and Chile, have already made fortification of flour with folic acid mandatory.
In these countries, the neural tube defect rate has gone down, as has the risk of cardiovascular disease.
There have been reports that folic acid may be linked to certain cancers, but SACN looked at the available data and said there was no good evidence to suggest that this would be a problem if flour were to be fortified.
Dr Pat O'Brien, a consultant obstetrician, said: "With any decision like this it is a question of weighing risks and benefits.
"In this case the benefits are huge and the potential risks are very small indeed."
Andrew Russell, of the Association for Spina Bifida and Hydrocephalus, said: "As far as we are concerned adding a further micro-nutrient to flour makes complete sense.
"It would prevent a good proportion of spina bifida pregnancies and would also benefit the health of the country as a whole."