In 1998, folic acid fortification of a large variety of cereal products became mandatory in Canada.
Canada was a country where the prevalence of neural-tube defects was historically higher in the eastern provinces than in the western provinces.
Dr Philippe De Wals and team from Canada assessed changes in the prevalence of neural-tube defects in Canada before and after food fortification with folic acid was implemented.
The study population included live births, stillbirths, and terminations of pregnancies because of fetal anomalies among women residing in 7 Canadian provinces from 1993 to 2002.
On the basis of published results of testing of red-cell folate levels, the study period was divided into prefortification, partial-fortification, and full-fortification periods.
The team evaluated the relationship between baseline rates of neural-tube defects in each province.
|Neural-tube defects decreased by 46% during fortification|
|The New England Journal of Medicine|
The magnitude of the decrease after fortification was implemented.
The researchers found a total of 2446 subjects with neural-tube defects were recorded among 1.9 million births.
The prevalence of neural-tube defects decreased from 1.6 per 1000 births before fortification to 0.9 per 1000 births during the full-fortification period, a 46% reduction.
The team noted that magnitude of the decrease was proportional to the prefortification baseline rate in each province.
The researchers found that geographical differences almost disappeared after fortification began.
The observed reduction in rate was greater for spina bifida than for anencephaly and encephalocele.
Dr De Wals' team concluded, "Food fortification with folic acid was associated with a significant reduction in the rate of neural-tube defects in Canada."
" The decrease was greatest in areas in which the baseline rate was high."