Prior lactation reduces future diabetic risk through sustained postweaning effects on insulin sensitivity.

Breastfeeding for ≥12 mo is recommended for optimal infant nutrition but may hold maternal benefits as well. Indeed, lactation has been associated with lower long-term risk of diabetes in the mother, but the mechanism by which it imparts sustained postweaning effects on glucose tolerance remains unclear. In this context, we postulated that lactation could potentially induce postweaning beneficial effects on glucose tolerance by modifying the natural history of insulin sensitivity and/or pancreatic β-cell function over time. Thus, in this study, we evaluated the relationships between duration of lactation [≤3 mo (n = 70), 3-12 mo (n = 140), and ≥12 mo (n = 120)] and trajectories of insulin sensitivity/resistance, β-cell function, and glycemia over the first 3 yr postpartum in a cohort of 330 women comprising the full spectrum of glucose tolerance in pregnancy, who underwent serial metabolic characterization, including oral glucose tolerance tests, at 3 mo, 1 yr, and 3 yr postpartum. The prevalence of dysglycemia (pre-diabetes/diabetes) at 3 yr postpartum was lower in women who breastfed for ≥12 mo (12.5%) than in those who breastfed for ≤3 mo (21.4%) or for 3-12 mo (25.7%)(overall P = 0.028). On logistic regression analysis, lactation for ≥12 mo independently predicted a lower likelihood of prediabetes/diabetes at 3 yr postpartum (OR = 0.37, 95% CI 0.18-0.78, P = 0.009). Notably, lactation for ≥12 mo predicted lesser worsening of insulin sensitivity/resistance (P < 0.0001), fasting glucose (P < 0.0001), and 2-h glucose (P = 0.011) over 3 yr compared with lactation ≤3 mo but no differences in β-cell function (P ≥ 0.37). It has thus emerged that adherence to current breastfeeding recommendations reduces future diabetic risk through sustained postweaning effects on insulin sensitivity/resistance but not β-cell function.