A new study conducted by researchers at Oxford Population Health has found that the risk of babies developing a neural tube defect during pregnancy was halved in countries with mandatory folic acid fortification of cereal grains compared with countries without any folic acid fortification. The study is published in eClinicalMedicine.
Folic acid supplements are highly effective for prevention of neural tube defects, which are responsible for conditions such as anencephaly (a defect of the brain) and spina bifida (a defect of the spinal cord). Previous studies had suggested that folic acid fortification may also lower blood levels of homocysteine (an amino acid), which has been associated with higher risk of stroke. Little is known about the effects of different types of folic acid fortification on blood levels of folate, risks of neural tube defects and risks of stroke in worldwide populations.
Data were collected on 193 member states of the World Health Organization (WHO). The report compared the impact of different folic acid fortification types on blood folate levels by country and year and assessed whether these were associated with differences in risks of neural tube defects or stroke.
- Most of North America, South America, Australia, and New Zealand implemented mandatory folic acid fortification and these countries added specified amounts of folic acid to staple foods such as wheat flour, maize, or rice;
- Most of Europe, China, and parts of Africa implemented voluntary folic acid fortification and in these countries governments issued food guidance to food manufacturers on the addition of folic acid to specified food products. Many countries in Eastern Europe and Africa have not yet implemented any folic acid fortification;
- People who were living in countries with mandatory folic acid fortification had folate levels that were three-four times higher than those without any folic acid fortification;
- Higher average levels of folate in blood samples (over 25 nmol/L) were found in 100% of countries with mandatory fortification, 15% of countries with voluntary fortification, and 7% of countries with no effective folic acid fortification;
- The number of neural tube defects in countries with mandatory folic acid fortification were 50% lower (4.19 per 10,000 births) than countries with no folic acid fortification policies (9.66 per 10,000 births), but the number of neural tube defects in countries with voluntary fortification were only 20% lower (7.61 per 10,000 births) than countries with no folic acid fortification;
- However, folic acid fortification policies had no significant effects on risks of death from stroke in countries with different fortification measures.
Dr Matthew Quinn, lead author of the study at Oxford Population Health, said ‘Our study demonstrated that mandatory folic acid fortification policies were associated with much greater mean levels of blood folate and the lowest risks of neural tube defects. When looking at folate levels in the blood, we also found that mandatory fortification policies helped to narrow the gap between richer and poorer groups of people by reducing the number of neural tube defects across the board. Even when considering high income countries with relatively extensive voluntary fortification, there is still evidence that it is ineffective in maintaining adequate folate levels in people from poorer backgrounds.’
Professor Robert Clarke, Emeritus Professor of Epidemiology and Public Health Medicine at Oxford Population Health, said ‘Mandatory folic acid fortification is associated with between 50-100% increase in the average levels of folate present in blood and 25-50% lower numbers of cases of neural tube defects when compared with no fortification. Despite this, there are still many countries, particularly in Eastern Europe and Africa, where there are no national-level policies in place to ensure that the diets of people living in those countries are supplemented with folic acid. While the UK Government signalled its intention to implement mandatory folic acid fortification for non-wholemeal flour products in September 2021, it has not yet implemented this policy.’