Mothers who nurse their babies now have another reason to continue as long as they can: longer periods of breastfeeding are associated with a lower risk of diabetes even decades later, a U.S. study suggests. Pediatricians recommend that mothers exclusively breastfeed infants until they’re at least six months old because it can reduce babies’ risk of ear and respiratory infections, sudden infant death syndrome, allergies, obesity and diabetes. Mothers are advised to continue breastfeeding for at least one year, a practice that previous research has linked to a lower risk of depression, obesity, and certain cancers. For the current study, researchers examined data on 1,238 mothers without diabetes at the outset. Over the next 25 years, 182 women developed diabetes. Compared to women who didn’t breastfeed at all, mothers who nursed babies for at least six months were 48 percent less likely to develop diabetes.

All of the women had at least one baby during the study, and most of them did breastfeed. Overall, 418 mothers, or 34 percent, nursed infants for up to six months. Another 268 women, or 22 percent, breastfed for six to 12 months, and 230 mothers, or 19 percent, nursed their babies for a year or more. Among women who didn’t breastfeed at all, 10 of every 1,000 typically developed diabetes each year, the study found. That dropped to fewer than 7 cases for every 1,000 people each year for women who nursed babies for up to six months, and fewer than 5 cases for women who nursed up to one year and fewer than 4 cases for mothers who breastfeed for longer. A diabetes diagnosis after pregnancy was much more common among women who developed a version of the condition known as gestational diabetes while they were pregnant. But longer periods of breastfeeding were still associated with a lower risk of diabetes later on, even for women who did experience gestational diabetes, researchers report in JAMA Internal Medicine.