A new Irish study of folic acid has shown that lower doses than previously advocated are likely to be as effective in helping the prevention of birth defects.
The study, carried out at the Coombe Women's Hospital in Dublin, is published in the latest edition of the Lancet medical journal. Folic acid supplements are known to prevent neural tube defects (NTDs), birth defects affecting the brain or spinal cord.
The findings are significant because efforts to date by the departments of health in Ireland, the UK and the US, to encourage women to take folic acid tablets have not been very successful, according to Dr Michael Turner, Master of the Coombe.
"This lack of success has forced consideration of mandatory fortification of food such as flour. However, there has been concern that adding high dosages of folic acid to flour could result in too high an oral intake of folic acid precipitating pernicious anaemia, especially in the elderly," said Dr Turner, who called for a policy of food fortification in Ireland.
The study, led by Dr Sean Daly, a consultant obstetrician, treated a group of women of child-bearing age with different doses of folic acid tablets for six months to determine how much was needed to raise their blood folate to a level known to protect against neural tube defects. By international standards Ireland has a high incidence of NTDs.
The study found that 100 micrograms of folate as a tablet supplement a day could decrease NTD risks by 22 per cent. Doubling this intake would halve that risk again. However, a further doubling of folate gave only a nominal improvement in reducing the risk.
Dr Turner said it was important for women who may become pregnant to continue to take folic acid supplements. He said a policy of supplementing food was important because women who were socially disadvantaged and those who had unplanned pregnancies were known not to take folic acid.
Giving folic acid tablets to women of child-bearing age has had only a limited success, he said. "For this reason, a flour fortification policy has been advocated, and in fact is about to be implemented in the USA, and is under consideration by a Department of Health committee in Ireland," Dr Turner said.
One hundred female staff from the Coombe participated in the study. Dr Turner said the participants had shown a very high level of commitment. The research team included members from Trinity College Dublin, the Health Research Board and the National Institute of Child Health and Human Development.