Human milk and total milk intakes of mixed fed infants: a cross-sectional study of infants aged 7–10 months

BACKGROUND/OBJECTIVES: There is a paucity of data on the volume of human milk consumed by infants, particularly in later infancy (> 6 months). The objective was to estimate human milk intakes and total infant milk intakes (i.e. including infant formula), and describe associated correlates in New Zealand (NZ) infants aged 7–10 months. SUBJECTS/METHODS: First Foods NZ (FFNZ) was a cross-sectional study that investigated infant feeding in NZ (July 2020-February 2022). Human milk intakes were obtained using the dose-to-mother stable isotope technique in a subset of breastfeeding mother-infant dyads. Infant formula intake was determined from 24-h recalls. Sociodemographic information was collected through questionnaires, and anthropometric measurements made. Total infant milk intake referred to human milk and infant formula. RESULTS: The breastfeeding sub-study comprised 157 mother-infant dyads whose infant milk was fully or partially human milk, and 217 non-breastfeeding dyads. All infants consumed solid foods. The mean (SD) human milk intake was 785 (264) g/day, higher in those consuming only human milk and no infant formula (828 g/day), and decreasing with age. Total infant milk intakes were around 820 g/day, regardless of milk type. Factors associated with both human milk and total infant milk intakes were infant age, BMI z-score, and maternal education. Maternal BMI and demand feeding were also related to human milk intakes. There was no difference in milk intake by season. CONCLUSIONS: This study provides valuable insight into human milk intakes during late infancy in NZ infants (7–10 months), improving our ability to accurately assess nutritional intakes and nutrient adequacy of infants.