Mothers who lactate for at least 6 months face a lower long-term risk for diabetes than their nonlactating peers, a prospective study in JAMA Internal Medicine finds.

U.S. researchers studied over 1200 white and black women aged 18–30 without diabetes at baseline who had at least one live birth during a mean 25 years' follow-up. The incident rate of (nongestational) diabetes during this period was 6.6 per 1000 person-years.

After multivariable adjustment — which accounted for factors like gestational diabetes, weight, physical activity, and family history — women who lactated for a total of either 6–12 months or 12 months or longer had about half the risk for diabetes as those who didn't lactate at all. The protective effect was seen regardless of race.

The researchers note that lactating women have lower circulating glucose levels and less insulin secretion. They suggest that increasing resources to improve breast-feeding rates "may be offset by lower health care costs associated with prevention of chronic disease."