Hundreds more birth defects could be prevented every year if the Government increased planned levels of folic acid fortification in flour, according to experts.
New legislation will require all producers to add folic acid to non-wholemeal wheat flour from the end of 2026.
But researchers led by University College London claim the planned amount — 250 micrograms per 100g — is too low. Folic acid, or vitamin B9, is found in foods such as leafy greens, asparagus, eggs and oranges.
It plays an important role in early pregnancy and development of the baby’s brain, skull and spinal cord. Deficiency is a leading cause of neural tube defects, which can cause serious and debilitating conditions including spina bifida.
Flour is already fortified with calcium, niacin, thiamine and iron. The Government says that adding folic acid will reduce neural tube defects by around 20%, preventing 200 cases of brain and spine defects every year.
However, the experts argue that the level of folic acid should be increased fourfold to 1mg per 100g in order to prevent 800 cases per year.
Professor Sir Nicholas Wald, a specialist in preventative medicine at UCL, said: “Fortifying all flour and rice to a higher level of fortification would prevent many more serious cases of disability.
“Our new findings show the evidence is consistent on this, despite past disagreement among researchers. Preventing about four out of five neural tube defects instead of one out of five would be a major public health benefit.”
Pregnant women are recommended to take 400 micrograms of folic acid every day until 12 weeks, and the fortification of flour will be an additional measure. Some women at higher risk take 5mg per day.
Prof Wald and his colleagues analysed two major studies in Ireland and China which involved 56,000 and 230,000 women, respectively.
Both looked at blood folate levels based on folic acid supplementation and incidence of neural tube defects.
The researchers concluded that the original authors of those studies had misinterpreted the evidence and consequently underestimated the optimal folate level.
When they replotted the data for the relationship between folate levels and defects on a logarithmic scale, they found each doubling of serum folate was linked to an approximate halving of the risk.
Prof Wald also warned that plans to limit fortification to non-wholemeal wheat flour “would exclude women who eat wholemeal bread and communities that eat rice as their carbohydrate staple”.
He added: “This new research resolves uncertainty over how much folic acid is enough for fully effective fortification.”
Concerns have been raised that higher levels of folic acid fortification could lead to people exceeding the recommended daily limit.
The NHS warns that taking more than 1mg per day can mask the symptoms of anaemia caused by a vitamin B12 deficiency, which can damage the nervous system if untreated.
But the researchers argued that this fear was “unfounded” because diagnosis of nerve damage linked to B12 does not rely on detection of anaemia.
They wrote: “On scientific grounds, therefore, the ‘tolerable upper intake level’ of folic acid can be abandoned.”
A Department of Health and Social Care spokesperson said the plans were based on a “clear consensus” about the correct level of fortification.
The spokesperson added: “The action we have taken will help reduce life-changing brain and spinal defects by around 20% and give women greater piece of mind throughout pregnancy.
“Public health programmes must take account of all available scientific evidence, and there is a clear consensus that this level of fortification is balanced and offers substantial benefits.
“Levels of folic acid fortification and health impacts will be kept under review.“
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