Breastfeeding as a Potential Factor Related to Preservation of Insulin Secretion in Youth with Recently Diagnosed Type 2 Diabetes: The SEARCH Nutrition Ancillary Study

Nutrition in infancy has been linked with long‐term effects on obesity, insulin‐resistance and type 2 diabetes. The SEARCH for Diabetes in Youth Case‐Control Study reported a protective effect of exclusive breastfeeding (versus never) on type 2 diabetes in childhood of 0.43 (95% CI 0.19–0.99), with potential mediation through childhood weight status. However, the impact of breastfeeding on insulin secretion in youth with type 2 diabetes has not been explored. Using data from the SEARCH Nutrition Ancillary Study we tested the hypothesis that breastfeeding is associated with a higher level of insulin secretion (measured by fasting C‐peptide‐FCP) shortly after diagnosis and a slower rate of decline over time among youth with type 2 diabetes, independent of onset age, sex, race/ethnicity, maternal diabetes status and baseline insulin sensitivity. Participants included 170 youth with type 2 diabetes with a mean age of diagnosis of 14.3 (SD=2.5) years. Breastfeeding initiation and duration was reported by mothers and categorized as: never breastfed (n=116), low breastfeeding duration of 1 day to 6 months (n=33) and adequate breastfeeding duration of ≥ 6 months (n=39). FCP levels were measured from longitudinally collected fasting blood samples obtained at an average of 19.9 (SD=19.8) months, 25.2 (SD=8.1) months, 37.7 (SD=8.2) months and 74.2 (SD=10.1) months after diagnosis of type 2 diabetes. Due to a previous observation of a skewed distribution of FCP levels, values were log transformed for the analyses. A linear mixed effect model was used to test the relationship between breastfeeding exposure categories and FCP levels over time with a random effect for duration of diabetes at the time of sample measurement. In a model adjusted for sex, race/ethnicity, age at diagnosis, parental education level and family history of diabetes, there was not a significant difference in the change of FCP over the 60 months after diagnosis by breastfeeding status (p=0.4). The monthly decrease in FCP was −0.7% for those never breastfed, −1.1% for those with low breastfeeding history, and −1.2% for those with adequate breastfeeding history. FCP levels (with 95% CI) for youth with type 2 diabetes at 60 months post diagnosis were 2.53 ± 1.16 ng/ml, 2.03 ± 1.21 ng/ml, and 2.92 ± 1.23 ng/ml, respectively, for youth who were never breastfed, those with low breastfeeding history and those with adequate breastfeeding history, (p=0.5). In conclusion, our study of a diverse population of youth with recently diagnosed type 2 diabetes suggests that breastfeeding is not associated with insulin secretion preservation. Our findings are limited by a study population that already has type 2 diabetes at a mean disease duration of nearly 20 months at the baseline visit; thus the possibility remains that any protective effects of breastfeeding are lost prior to diagnosis and/or earlier in the diabetes disease course. Support or Funding Information The SEARCH Nutrition Ancillary Study is funded by National Institutes of Health (NIH)/National Institute of Diabetes and Digestive and Kidney Disease R01 DK077979 (E,J.M.‐D and N.S.T. co‐principal investigators). SEARCH for Diabetes in Youth is funded by the Centers for Disease Control and Prevention (PA numbers 00097, DP‐05‐069, and DP‐10‐001) and supported by the National Institute of Diabetes and Digestive and Kidney Diseases.