Mothers who breastfeed for at least six months cut the risk of diabetes during their child-bearing years by half, a study has found.
Scientists analysed 30 years worth of data from a major US investigation of heart disease risk factors.
About 5,000 adults aged 18 to 30 joined the coronary artery risk development in young adults (Cardia) study between 1985 and 1986.
Women who breastfed for six months or more were 47% less likely to develop type 2 diabetes than those who chose not to breastfeed, the researchers found.
Mothers breastfeeding for six months or less reduced their risk of diabetes by a quarter.
Lead investigator Dr Erica Gunderson, from the US care provider Kaiser Perminante, said: “We found a very strong association between breastfeeding duration and lower risk of developing diabetes, even after accounting for all possible confounding risk factors.”
The findings, published in the journal Jama Internal Medicine, add to growing evidence that breastfeeding has protective effects for both mothers and their babies.
Previous research has shown that it lowers a mother’s risk of breast and ovarian cancer.
Dr Gunderson added: “The incidence of diabetes decreased in a graded manner as breastfeeding duration increased, regardless of race, gestational diabetes, lifestyle behaviours, body size, and other metabolic risk factors measured before pregnancy, implying the possibility that the underlying mechanism may be biological.”
Hormones associated with breastfeeding may have an effect on the pancreatic cells that blood insulin levels, the scientists believe.