Folic acid should be added to bread on a mandatory basis, the Food Standards Agency has advised government.
It says the move could stop dozens of babies developing spina bifida, as the vitamin plays a key role in foetal growth.
Women are advised to take supplements before becoming pregnant, but many do not do so, or take them too late.
Research has linked folic acid to a raised cancer risk, but the FSA said the evidence was not convincing.
The US and Canada started fortification of bread flour in the late 1990s, and some of the subsequent research has pointed to an increase in cases of bowel cancer.
However the Scientific Advisory Committee on Nutrition, which advises the FSA, said this evidence was insubstantial and that any increase in cases could be down to improved screening.
It did, however, recommend that those deemed to be at greater risk of colon cancer should receive precautionary advice on taking extra supplements containing folic acid, and that the situation should be monitored.
Between 700 and 900 pregnancies are affected by spina bifida every year. Experts estimate this could be reduced by up to 18% with fortification.
There are also positive health implications for the entire population, as inadequate levels of folate have been linked to a range of diseases - including cancer.
Last month there were calls for all Scottish women to take folic acid - even those not planning a family - after 15 babies were born with spina bifida since the start of the year.
Folic acid is a synthetic form of folate, a B vitamin found in a wide variety of foods including liver and green leafy vegetables.
The body cannot store it, so it must be ingested daily via supplements or folate-rich foods.
The vitamin is known to prevent neural tube defects in foetuses, but many women do not take it - in part because pregnancies are often unplanned and can go unnoticed for many weeks.
As well as cutting the incidence of spina bifida, latest research from Canada also suggests it can reduce the risk of congenital heart problems in babies.
Cereal has long been fortified on a voluntary basis by manufacturers, but suggestions that bread must be supplemented by law have been rejected by those who argue it is tantamount to mass medication.
Concerns about the how the potential risks weigh up against the benefits have been expressed.
As well as suggestions of a link with colorectal cancer, studies have also shown it may speed up cognitive decline in elderly people with other B vitamin deficiencies.
SACN did look at these issues for a report in 2007, which ultimately recommended fortification. But following publication of that report it was also asked to analyse two more studies relating to bowel cancer.
The FSA said that since SACN's advice on fortification has not changed significantly as a result, its own recommendation in favour remained the same.
The government's Chief Medical Officer Sir Liam Donaldson is expected to discuss the issue with counterparts in Scotland, Wales and Northern Ireland having received the updated advice.
Legislation would be necessary to introduce the measure, and it would also mean stricter controls on fortified foods like cereals to ensure people did not exceed recommended daily intakes.
Dr Sian Astley of the Institute of Food Research said mandatory bread fortification was premature.
"You cannot fault SACN for their review of the evidence, the problem is that it is a very fast-moving situation," she said.
"Folic acid as we are given it is not a nature identical substance, and so we metabolise it in a different way. We don't know the exact effects of this and much is not proven one way or the other.
"We really should be waiting for the full picture to emerge from the US - they are 10 years ahead of us with this - before we make a decision on this front."
A spokesman for the Department of Health said: "We will now consider their recommendation for the introduction of mandatory fortification of flour with folic acid alongside controls on voluntary fortification."