At its open board meeting in London last month, the Food Standards Agency (FSA) asked its board to consider the latest research for and against fortification, and presented the draft opinion of the Scientific Advisory Committee on Nutrition (SACN) that neither continuing voluntary fortification nor raising more awareness of folate amongst women of childbearing age will alone have an effect on the incidence of neural tube defects (NTDs).
This led the FSA to say in a document published in advance of the meeting that: "Bread would be an appropriate vehicle because it has a relatively uniform consumption across subgroups of the population."
However the SACN has now said that it needs more time to look at additional evidence of the risks and benefits of fortification, delaying the publication of its final report.
This means that the FSA is unable to go ahead with its consultation planned for this month - and no timetable for the next steps in the decision-making process will be drawn up until the final report is forthcoming.
A spokesperson for the FSA told NutraIngredients.com that the ongoing investigations relate to increasing folate intake over 1mg per day.
A level of the fortification has not yet been proposed, but it is thought to be likely to be between 100 and 450 microgrames per 100g.
"The nature of science is that emerging evidence is always coming forward," said the spokesperson, adding that the SACN did not want to put forward a recommendation that did not consider all the available evidence.
As to whether the ongoing investigations could cause SACN to dramatically alter its position, she said: "We don't know. It's possible that could happen."
The most common NTDs are spina bifida and anencephaly, both of which occur in the very early stages of pregnancy, often before women are aware that they are expecting.
It is estimated that between 700 and 900 pregnancies are affected by NTDs in the UK each year (including terminations as a result of detection but not including miscarriages).
Dietary folate is known to reduce the risk of these conditions. It occurs naturally in foods such as grains, lentils, chick peas and green leafy vegetables. Folic acid is a synthetic form of the nutrient which, according to the National Council on Folic Acid in the US, is actually better absorbed by the human body.
The FSA last considered mandatory fortification in 2002, but the SACN decided not to adopt it at that time because of concerns that folate consumption in excess of 1000 micrograms (1mg) per day could delay the detection of vitamin B12 deficiency (which can have severe neurological consequences) in older people.
Since then, some research has indicated that B12 deficiency would be masked only with folate consumption of more than 5000 micrograms per day.