Adding folic acid to bread in an attempt to cut birth defects may lead to serious health problems, scientists have warned.

©Adam, Inc.
Folate (folic acid) is necessary for the production of red blood cells and for the synthesis of DNA (which controls heredity and is used to guide the cell in its daily activities). Folic acid also helps with tissue growth and cell function. In addition, it helps to increase appetite when needed and stimulates the formation of digestive acids.

The Government is considering whether to fortify flour with the vitamin as a way of reducing cases of spina bifida after the Food Standards Agency approved it earlier this year.

But scientists have found that the synthetic supplement can easily saturate the liver and that the body will struggle to break it down, leading to health problems.

Previous studies have also linked unmetabolised folic acid in the blood to an increased risk of bowel, prostate and breast cancer.

A team from the Institute of Food Research, which conducted the latest study, warned that a liver flooded with folic acid will release it into the blood undigested, which could create major problems for people already in poor health.

It had previously been thought that folic acid would be broken down in the stomach, in the same way as natural forms of the substance.

Writing in the British Journal of Nutrition, the scientists said the full impact of putting folic acid in food could only become apparent in 20 years.

Dr Sian Astley from the institute said: "Fortifying UK flour with folic acid would reduce the incidence of neural tube defects (such as spina bifida).

"However, with doses of half the amount being proposed for fortification in the UK, the liver becomes saturated and unmetabolised folic acid floats around the blood stream.

"This can cause problems for people being treated for leukaemia and arthritis, women being treated for ectopic pregnancies, men with a family history of bowel cancer, people with blocked arteries being treated with a stent (an internal splint) and elderly people with poor vitamin B status."

She said it also increased the likelihood of multiple births for women undergoing IVF treatment. Folic acid, found in many foods including leafy green vegetables, is essential for pregnant women.

Those who don't get enough run a serious risk of their baby being born with spina bifida, a condition which leaves part of the spinal cord exposed, creating life-long disability.

In America, flour has been fortified with folic acid since 1996 and the incidence of spina bifida has dropped by more than 20 per cent.

In the UK, between 700 and 900 pregnancies every year are affected by neural tube defects. Fortifying bread could prevent around 160, it is claimed.

But scientists also warn that if people are already getting enough in their diets then the extra dose could be harmful. Folic acid is known to feed cancerous cells and help them grow.

It has been predicted that adding more folic acid to the nation's diet could lead to more than 3,000 new cases of colon cancer, a rise in prostate cancer and put as many as 150,000 elderly people at risk of anaemia and memory problems.

In a statement, the Food Standards Agency said its recommendation in favour of adding folic acid was made after an "extensive and scientifically robust assessment".

It said: "The FSA Board would not have recommended mandatory fortification if the scientific evidence suggested that there were unacceptable health risks for some groups.

"As part of the process, an expert committee of scientists considered the evidence regarding unmetabolised folic acid and they concluded that the data in humans was insufficient to assess any associated risks.

"They also examined in detail the potential cancer risks to some groups from high folic acid consumption."

The FSA added that it had recommended controls on voluntary fortification and clear guidance on the use of folic acid.