Fortifying flour and pasta products with folic acid appears to cut the number of babies born with congenital heart disease, the most common of all birth defects, Canadian researchers said on Tuesday.

While food fortification is not mandatory in Europe, a 1998 Canadian requirement has led to a 6 percent drop each year in the number of such defects in Quebec, they reported in the British Medical Journal.

"These findings support the hypothesis that folic acid has a preventive effect on heart defects," Louise Pilote of McGill University in Montreal and colleagues wrote.

"Public health measures to increase folic acid intake were followed by a decrease in the birth prevalence of severe congenital heart defects."

Currently 67 countries fortify wheat flour, 47 of them by mandate, Helena Gardiner of Imperial College in London and Jean-Claude Fouron of CHU Sainte-Justine University Hospital Center in Montreal noted in an editorial.

Folic acid helps the body make healthy new cells. It is important that women get enough of it before and during a pregnancy to prevent major birth defects involving a baby's brain or spine.

Leafy green vegetables, fruits, dried beans peas and nuts contain folic acid. It can be added to grain products or taken as a dietary supplement.

Even with fortification, many women do not get enough folic acid. In their study, Pilote and colleagues identified all infants born in Quebec with severe congenital heart defects between 1990 and 2005.

Their analysis showed no change in how many babies were born with severe heart defects in the nine years before fortification. But there was a 6 percent decrease annually for each of the seven years after fortification began.

The dip may seem modest but given the complex treatment for the often fatal heart defects, even a small reduction can significantly reduce costs health care costs, the researchers said.