The number of babies born with severe congenital heart defects has decreased after mandatory fortification of grain products with folic acid in Canada, concludes a large study published on bmj.com today.
It is widely known that taking folic acid before conception and in early pregnancy reduces the risk of neural tube defects such as spina bifida. Some studies suggest that folic acid may also decrease the birth prevalence of congenital heart disease, the most common of all birth defects, but the evidence is still inconclusive.
So researchers assessed the impact of folic acid fortification policies on the birth prevalence of severe congenital heart defects in Quebec, Canada, where fortification of flour and pasta products with folic acid has been mandatory since 1998.
Mandatory food fortification has not been adopted in Europe.
Using administrative databases, they identified all infants (live and stillborn) with severe congenital heart defects in Quebec over a 16 year period (1990 to 2005). Data were analysed in two time periods (before and after fortification) to estimate the change in prevalence of severe heart defects within the population.
During the study period there were 1.3 million births in Quebec and 2,083 infants born with severe heart defects, corresponding to an average birth prevalence of 1.57 per 1,000 births.
The time trend analysis showed no change in the birth prevalence of severe heart defects in the nine years before fortification, while in the seven years after fortification there was a significant 6% decrease per year.
Further analysis made little difference to the results, suggesting that the decreasing trend after fortification did not occur by chance, and supporting the theory that intake of folic acid around conception reduces the risk of severe congenital heart defects.
The authors suggest the results were not likely caused by chance because the timing of the observed effect coincided exactly with the timing of the fortification; there is biological plausibility for this association, and most other factors that are known to increase the birth prevalence of severe congenital heart defects, such as older maternal age, medication use, or obesity, have gradually increased over the study period in Quebec.
An average 6% drop per year may seem modest, say the authors. But, given that treatment for heart defects in infancy is highly complex and is associated with high infant mortality rates, even a small reduction in the overall risk will significantly reduce the costs associated with the medical care of these patients and the psychological burden on patients and their families.
They also suggest that their results may have underestimated the true impact of folic acid on the birth prevalence of severe congenital heart defects, and call for further population-based studies to confirm these findings.
Such studies raise important questions about whether food fortification is an effective strategy, say two heart experts in an accompanying editorial. For example, are the current levels of fortification sufficient to significantly reduce the rates of congenital malformations, and is food fortification harmful to some people?
As the population becomes more obese, rates of type 2 diabetes increase and nutritional habits remain poor, the prevalence of congenital heart disease may increase, they write. So, rather than considering fortification targeted at populations, should we find more effective interventions to target women of child bearing age?