Breast Milk Macronutrients and Child Growth and Neurodevelopment in a Lactation Cohort in Rural Bangladesh.

BACKGROUND

Limited data exist on the relationship between breast milk macronutrient/energy concentrations and child outcomes in settings with high maternal undernutrition.

OBJECTIVES

This study aims to determine associations of breast milk macronutrient (protein, fat, carbohydrate) and energy concentrations with child growth and neurodevelopment.

METHODS

In this observational lactation cohort of 99 mother-infant dyads from Sylhet, Bangladesh, mothers provided hand-expressed breast milk samples at 2 and 5 mo postpartum. Infant anthropometrics were obtained at birth, 3, 6, 12, and 24 mo; neurodevelopment was assessed at 24 mo using the Bayley Scales of Infant and Toddler Development-III. Macronutrient concentrations were measured using midinfrared spectroscopy. Associations with growth and neurodevelopment z-scores were estimated using mixed models and linear regression, adjusted for a priori confounders. Primary outcomes were length-for-age z-score (12 mo) and cognitive z-scores (24 mo) in relation to 2-mo protein concentration.

RESULTS

Breast milk samples were provided at 2 (n = 98) and 5 mo (n = 87). We found no significant associations between 2-mo protein and 12-mo length-for-age z-scores or 24-mo cognitive z-scores. Higher 2-mo fat (g/dL) was associated with lower weight-for-age z-scores at 3 mo [b: -0.12 (95% confidence interval (CI): -0.24, -0.005)] and lower head circumference-for-age z-scores at 3 [-0.20 (-0.32, -0.09)], 6 [-0.19 (-0.31, -0.08)], and 12 mo [-0.17 (-0.29,-0.06)]. Similarly, 2-mo energy (kcal/dL) was inversely associated with 3-mo weight-for-age z-scores [-0.01 (-0.03, -0.001)] and head circumference-for-age z-scores at 3 [-0.02 (-0.04, -0.01)], 6 [-0.02 (-0.03, -0.01)], and 12 mo [-0.02 (-0.03, -0.01)]. Higher 2-mo carbohydrate (g/dL) was associated with higher motor z-scores [1.08 (0.06, 2.09)], and higher 5-mo carbohydrate with higher cognitive z-scores [1.10 (0.15, 2.05)].

CONCLUSIONS

Protein concentrations were not associated with linear or cognitive outcomes in this cohort. Our findings suggest that future studies targeting infant outcomes may optimally be designed to account for factors beyond macronutrient concentration, such as daily milk volume intake, that may impact infant growth and development.