Human milk composition differs by maternal BMI in the first 9 months postpartum

Abstract

Background: Studies indicate that maternal weight status modulates human milk composition; however, results are conflicting.

Objectives: Our objective was to examine the relation between maternal body composition and human milk macronutrients and bioactive components and also their association with infant daily intakes and body composition.

Methods: Human milk samples were obtained from a longitudinal study (NCT01131117) in normal weight (NW: 18.5-24.9 kg/m2, n = 88) and overweight/obese (OW: 25-35 kg/m2, n = 86) women between 0.5 and 9 mo postpartum. Macronutrient content was estimated using mid-infrared spectroscopy. Leptin, insulin, and C-reactive protein (CRP) were measured using electrochemiluminescence immunoassays. Infant body composition was obtained using quantitative MRI. Linear mixed models were adjusted for postpartum age and infant sex.

Results: Human milk in OW mothers was higher in fat and protein and lower in carbohydrate content at some time points compared with that in NW mothers. Human milk leptin, insulin, and CRP concentrations were higher in OW mothers compared with NW mothers, with infants of OW mothers exposed to 1.5-2.5 times higher concentrations of leptin and insulin compared with infants of NW mothers. Similar results were observed when concentrations were normalized to infant daily intake and body weight. The effect sizes of infant daily intakes associated with infant growth parameters were small for macronutrients [0.005-0.05 z-score units and 0.02-0.45 fat mass index (FMI) or fat-free mass index units per unit of change in composition, P < 0.05]. Larger effect sizes were seen with human milk insulin and leptin (0.24 z-score units and 0.37-1.15 FMI units per unit of change in composition, P < 0.05).

Conclusions: These findings demonstrate that infants of OW mothers are exposed to higher concentrations of insulin, leptin, and, to a lesser extent, CRP. The bioavailability of these 3 human milk bioactives and their mechanisms of action in the infant are unclear.This trial was registered at clinicaltrials.gov as NCT01131117.

Keywords: C-reactive protein; energy; human milk; insulin; leptin; macronutrients; obesity.

Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.

Figures

FIGURE 1

Cohort flow diagram. LTFU, lost to follow-up.

FIGURE 2

Estimated marginal means of human milk macronutrient concentration and intakes during the first 9 mo postpartum. Predicted macronutrient concentrations by maternal BMI (mean ± SEM) are based on linear mixed-effect models adjusting for postpartum age and infant sex. Infant daily intake models were also adjusted for infant feeding mode (exclusive compared with mixed). The solid lines indicate maternal NW (18.5–24.9 kg/m2), and the dotted lines indicate maternal OW (25–35 kg/m2). A significant interaction between postpartum age and maternal group was observed in the energy, fat, and protein intake models. For NW participants in composition models, n = 77, 73, 67, 63, 60, 53, 55, and 46 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For OW participants in composition models, n = 80, 74, 69, 68, 61, 54, 52, and 38 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For NW participants in intake models, n = 58, 55, 52, 51, 41, 32, 51, and 18 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For OW participants in intake models, n = 59, 60, 56, 53, 42, 40, 41, and 23 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. At each time point, *P < 0.05, **P < 0.01. NW, normal weight; OW, overweight.

FIGURE 3

Estimated marginal means of human milk leptin, insulin, and CRP concentrations and intakes during the first 9 mo postpartum. Predicted leptin, insulin, and CRP concentrations by maternal BMI (mean ± SEM) are based on linear mixed-effect models adjusting for postpartum age and infant sex. Infant daily intakes models were also adjusted for infant feeding mode (exclusive compared with mixed). Solid lines indicate maternal NW (18.5–24.9 kg/m2), and dotted lines indicate maternal OW (25–35 kg/m2). A significant interaction between postpartum age and maternal group was observed in the leptin intake model. For NW participants in composition models, n = 77, 73, 67, 63, 60, 53, 55, and 46 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For OW participants in composition models, n = 80, 74, 69, 68, 61, 54, 52, and 38 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For NW participants in intake models, n = 58, 55, 52, 51, 41, 32, 51, and 18 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. For OW participants in intake models, n = 59, 60, 56, 53, 42, 40, 41, and 23 at 0.5, 1, 2, 3, 4, 5, 6, and 9 mo, respectively. At each time point, *P < 0.05,**P < 0.01. CRP, C-reactive protein; NW, normal weight; OW, overweight.