The longer women breastfeed, the lower their risk of heart attacks, strokes and cardiovascular disease, report U.S. researchers in a study in the journal Obstetrics & Gynecology.

The study adds to a growing body of evidence suggesting breastfeeding has health benefits for both mother and baby.

Researchers at the University of Pittsburgh looked at data on nearly 140,000 post-menopausal women enrolled in the Women's Health Initiative, a study of chronic disease that began in 1994.

They found that compared to women who never breastfed, women who breastfed for one to six months in their lifetimes had a:

  • five per cent lower risk for high blood pressure
  • nine per cent lower risk for diabetes
  • seven per cent lower risk for high cholesterol.

Women who breastfed two years or more during their lifetimes had a:

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

An average of 35 years had passed since women enrolled in the study had last breastfed an infant, suggesting that the benefits from breastfeeding last a long time, said lead researcher Dr. Eleanor Bimla Schwarz, assistant professor of medicine, epidemiology, and obstetrics,

"We have known for years that breastfeeding is important for babies' health; we now know that it is important for mothers' health as well," said Schwarz.

"The longer a mother nurses her baby, the better for both of them... Our study provides another good reason for workplace policies to encourage women to breastfeed their infants."

Research has found that breastfeeding offers many health benefits to both mother and baby. The Breastfeeding Committee for Canada notes that breastfeeding offers protection for some women against breast cancer, ovarian cancer, endometrial cancer, osteoporosis and anemia.

The list of benefits for the baby is long, with breast milk credited with protecting against obesity, childhood cancers, allergies, and ear and stomach infections.

The Canadian Paediatric Society and Health Canada recommend exclusive breastfeeding for a baby's first six months of life.