Folic acid has been shown previously to dramatically decrease the incidence of neural tube defects (e.g. spina bifida) in newborns. Dr. Joel Ray, of the Departments of Medicine at U of T and St. Michael's Hospital, and co-researchers decided to examine the prevalence of Trisomy 21 (commonly known as Down Syndrome) following the introduction of folic acid fortification into most Canadian cereal grains by 1998. They examined prenatal and postnatal incidence rates of Trisomy 21 in Ontario, screening nearly 219,000 women prior to fortification and 118,000 women afterward. They found virtually no decline in the incidence of Trisomy 21 in relation to fortification.
However, Ray explains that folic acid and vitamin B12 are essential for the proper development of genes, which lie in chromosomes and are copied as cells divide. He says it's possible that part of the reason they saw no impact of folic acid fortification on Trisomy 21 rates is that the amount of folic acid intake was not high enough. But, he adds, another possibility may be that Trisomy 21 originates even before a woman is born.
"A woman's eggs are formed when she herself is a fetus in her mother's womb," says Ray. "So while taking folic acid may have no impact on the eggs of a woman now to prevent Trisomy 21, it may modify the eggs of her daughter to reduce the risk when she has her own child."
This research, published in the July 30 issue of the American Journal of Medical Genetics Part A, was supported by the Ontario Ministry of Health and Long-Term Care.