A group of UK doctors has urged the government to proceed with the move towards fortifying flour with folic acid to prevent birth defects.
Folic acid in bread could help cut cases of spina bifida
The Food Standards Agency approved the move in June this year, which is aimed at cutting the number of babies born with conditions such as spina bifida.
But the government called for a further review of recent studies linking folic acid to colon cancer.
Writing in the Lancet, the doctors said there was no evidence of a connection.
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 chief medical officer for England, Sir Liam Donaldson, sent a letter to the FSA in October to ask them to consider two recent studies on colon cancer and folic acid.
One study had looked at the effects of folic acid supplements in the prevention of colorectal adenomas - a type of benign tumour.
According to Professor Roger Bayston, associate professor for surgical infection at Nottingham University, the study found no reduction in adenoma risk but neither did the researchers find an increase.
Professor Bayston, who is also chairman of the medical committee of the Association for Spina Bifida and Hydrocephalus, also criticised suggestions that folic acid fortification in 1998 in the US and in 1999 in Canada had led to a rise in cases of colon cancer.
A paper published earlier this year had raised the possibility of a link.
But cases of colon cancer began to rise before the introduction of folic acid into bread flour, he said.
And there had been an increase in detection in the number of cancers in the late 1990s because of more widespread screening.
"The FSA and the chief medical officer can be confident in recommending that the government introduce the mandatory fortification of flour," said Professor Bayston.
He added the experts on the FSA committee had already very carefully considered the issue of possible cancer risks before making their recommendations.
"The issue has been delayed for many years, largely due to concerns which have turned out not to be well founded."
A spokesperson for the FSA said they would be considering the studies in question at a meeting next month but that they had already looked at the preliminary results.
Claire Williamson, nutrition scientist at the British Nutrition Foundation, said: "It is of paramount importance that the benefits and risks are considered in detail, before any policy decision at the population level is made."
Mandatory fortification has already been introduced in the US, Canada and Chile, where it has cut birth defect rates by up to half.