About 14 per cent of new mothers surveyed in Canada were exclusively feeding their newborns breast milk by six months of age as recommended. (CBC)

The longer a woman breastfeeds, the lower her risk of heart attacks and strokes seems to fall decades later, a new study suggests.

In the May issue of Obstetrics & Gynecology, researchers in the U.S. reported that women who breastfed for more than a year were 10 per cent less likely to develop the cardiovascular conditions than women who never nursed.

"The longer a mother nurses her baby, the better for both of them," said study author Dr. Eleanor Bimla Schwarz, a professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh.

"Our study provides another good reason for workplace policies to encourage women to breastfeed their infants," she added in a release.

The study looked at 139,681 postmenopausal women with an average age of 63 who were enrolled in the Women's Health Initiative.

On average, it had been 35 years since the women last breastfed.

Compared with women who never breastfed, those who breastfed two years or more during their lifetimes had:

• A 13 per cent lower risk for high blood pressure.
• A 12 per cent lower risk for diabetes.
• A 20 per cent lower risk for high cholesterol.

Shorter breastfeeding also showed benefits. Women who breastfed for one to six months had a nine per cent lower risk for diabetes, five per cent lower risk for high blood pressure and seven per cent lower risk of high cholesterol, compared with women who never breastfed.

Role of fat, hormones

The findings held after researchers took age, income, body mass index, diet, physical activity, and family history of heart disease into account, but it's possible that other factors such as stress could be playing a part.

It's thought that breastfeeding may lower the risk by reducing fat stores in the body. Hormones such as prolactin and oxytocin that are involved in producing and releasing milk may also have effects on a woman's heart.

Babies who are breastfed have fewer infections and respiratory illnesses and suffer fewer cases of diarrhea.

For mothers, research suggests breastfeeding reduces a woman's risk of ovarian and breast cancer later in life.

Health Canada and the Canadian Pediatric Society recommend that babies drink only breast milk for the first six months of life. Breastfeeding may continue for two years or more as new foods are added.

A national survey released last month by the Public Health Agency of Canada found 14 per cent of new mothers in Canada were exclusively feeding their newborns breast milk by six months of age.