Fortifying grain products with folic acid has led to a dramatic decline in the rate of birth defects such as spina bifida, a new study by Health Canada shows.

The proportion of babies born with neural tube defects in Newfoundland and Labrador dropped by 78 per cent after the federal government required folic acid to be added to flour, cornmeal and pasta, researchers found.

Dark green, leafy vegetables are high in folate. (Photo: John Bowman)
Dark green, leafy vegetables are high in folate. (Photo: John Bowman)

Folic acid is the synthetic form of folate, also called vitamin B-9, which is found in citrus fruits, nuts, liver and dark green, leafy vegetables.

The vitamin has many important functions in the body, but it was in the mid-1960s that scientists discovered that folate deficiency might be the cause of neural tube defects, in which the central nervous system fails to develop fully in the fetus.

Neural tube defects can lead to spina bifida, a defect of the spinal cord and back bones, and less common defects of the brain such as anencephaly, when the brain doesn't develop fully.

Scientists don't know how folic acid reduces the risk of neural tube defects in developing babies.

Since 1992, many medical authorities have told women of child-bearing age to take folic acid supplements.

The Canadian government introduced mandatory fortification of some foods with folic acid in 1998.

Continue to fortify food, scientists say

Dr. Catherine McCourt, with Health Canada's population and public health branch in Ottawa, and her colleagues studied the effects of folic acid fortification in women aged 19 to 44 and in seniors in Newfoundland and Labrador.

The study looked at women in St. John's, Nfld. and the rural area of Clarenville, Port Blandford in the Random Island area.

Historically, the province has had one of the highest rates of neural tube defects in North America, the researchers said in the Sept. 27 issue of BMC Pregnancy and Childbirth.

McCourt's team found the fortification boosted dietary intake of folic acid by 70 micrograms per day, on average.

The incidence of neural tube defects in the province fell by 78 per cent, from an average of 4.36 defects per 1,000 births between 1991 and 1997, prior to fortification, to an average of 0.96 defects per 1,000 births between 1998 and 2001.

"Based on these findings, mandatory food fortification in Canada should continue at the current levels," the researchers concluded.

There is no way to tease out the contributions of food fortification and supplement use on the decline of neural tube defects, the researchers noted.

"Public education regarding folic acid supplement use by women of childbearing age should also continue," the study's authors added.