Impact of Maternal Diet and Exercise on Human Milk Insulin

The impact of maternal phenotype, diet and exercise on bioactive components in human milk (HM) remains an area of active research. We aimed to determine if maternal diet, specifically the nature of her carbohydrate intake, correlated with the fasting concentrations of insulin in her breast milk. Maternal 3‐day diet records were collected at 2‐weeks and 4‐months postpartum from 48 exclusively breastfeeding women. Diets were analyzed by a registered dietitian at the Colorado Clinical and Translational Sciences Institute using the Nutrient Data System for Research (NDSR) software (2012). Fasting maternal blood and a mid‐feed HM sample were collected in the morning hours at 2‐weeks and 4‐months. Skim milk was generated via centrifugation and HM and maternal plasma insulin concentrations were measured via chemiluminescent ELISA. At 4‐months, mothers completed a Godin Leisure‐Time Exercise Questionnaire to characterize degree of physical activity. The cohort exhibited a wide range of caloric and fiber intakes. Maternal circulating insulin concentrations were highly correlated with HM insulin at both time points (p<0.0001). Increased consumption of insoluble fiber at 2‐weeks was associated with decreased concentrations of HM insulin (p=0.049, n=48, R2=0.08). While this association did not remain significant at 4‐months, increased consumption of added sugars and %kcal from carbohydrates at 4‐months were both positively associated with HM insulin concentrations (n=37; p=0.075, R2=0.07 and p=0.044, R2=0.08, respectively). These relationships between dietary carbohydrate quality and fasting HM insulin remained significant after controlling for maternal pre‐pregnancy BMI, age, total calories and maternal insulin concentrations. Maternal exercise score was not related to HM insulin.The quality of carbohydrate consumed at 2‐weeks and 4‐months postpartum was associated with HM insulin concentrations, suggesting that modifiable factors, such as diet, may impact bioactive components in HM. Recommendations to encourage fiber intake and limit added sugars may impact HM components; potential benefits to maternal health and infant outcomes warrant further investigation.Support or Funding InformationUniversity of Colorado Center for Women's Health Research; The Thrasher Research Fund; NIH/NIDDK: T32‐DK007658–21; NIH/NICHD F32‐HD0978068; The Colorado Clinical and Translational Sciences Institute NIH/NCATS UL1‐TR001082.