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In November 1998, the Canadian authorities introduced mandatory fortification of many cereal products with folic acid. They aimed to increase intake of folic acid by 30-70% in women of childbearing age and reduce the incidence of neural tube defects. It workedworked.
A close look at all live births, still births, and terminations for fetal anomaly in seven Canadian provinces found that the incidence of all neural tube defects fell from 1.58 per 1000 births before the legislation to 0.86 per 1000 births by 2002, a reduction of 46% (95% CI 40% to 51%). The effect was biggest in spina bifida (53% reduction), but fewer cases of anencephaly (38% reduction) and encephalocele (31%) were also seen. The Eastern provinces—which had the highest incidence to start with—benefited most. By 2002, fortification had wiped out this well documented east-west gradient.
Currently, Canadian millers add 0.15 mg of folate to each 100 g of flour or cornmeal and 0.20-0.27 mg to each 100 g of pasta. Experts estimate this gives everyone around 150 µg of extra folic acid a day. American cereals were also fortified in 1998, say the researchers. But the incidence of anencephaly and spina bifida combined fell by a more modest 28% south of the border.