Exclusive or partial breastfeeding and estimated protein intake in infancy: Associations with childhood growth and body composition at 7 years of age in the Odense Child Cohort

Background: Protein intake in infancy influences infant growth, body composition, and possibly metabolic programming later in life. Our objectives were to investigate whether macronutrient content in mother's own milk (MOM) differed between exclusive (EBF) or partial breastfeeding (PBF), including an estimation of protein intake (ePI) during the first 6 months of life. Second, to investigate associations of feeding type and ePI with childhood growth and body composition at 7 years.

Methods: In a subset of 150 participants from the Odense Child Cohort, MOM was analysed for macronutrient content using midinfrared transmission spectroscopy. Information on breastfeeding duration was collected through weekly SMS questionnaires and used to calculate ePI. Outcomes were weight-for-age z-scores (WAZ) and height-for-age z-scores (HAZ) from birth to 7 years, and body composition in terms of dual X-ray absorptiometry fat mass, fat-free mass and calculated indexes at 7 years.

Results: The macronutrient content in MOM did not differ between EBF and PBF, but ePI was significantly higher in PBF infants than in EBF infants at 6 months. We found no difference in WAZ or HAZ until 7 years of age according to feeding type, but within the PBF group, ePI was positively associated with 7-year WAZ (β = 0.001; 95% CI 0.000-0.003; p = 0.03) and HAZ (β = 0.002; 0.001-0.003;p = 0.007). ePI was not associated with body composition at 7 years.

Conclusion: Milk macronutrient content and childhood growth did not differ between EBF and PBF during infancy. Estimated protein intake in partially breastfed infants was positively associated with childhood growth, but not body composition, at 7 years of age.