Breast milk cytokines and infant growth trajectories in a low-income community in Bangladesh.

Abstract

Breast milk cytokines modulate immune function and may influence infant growth, yet longitudinal evidence remains limited, particularly in low-resource settings. This study examined associations between milk cytokines measured within six weeks postpartum and infant growth trajectories from 3 to 12 months in a low-income community in Dhaka, Bangladesh. Data from 237 mother-infant dyads were drawn from a prospective cohort study. Cytokines were quantified in breast milk (IL-1β, IL-6, IL-8, IL-10, TNF-α, IFN-γ). Anthropometrics at 3, 6, 9, and 12 months were converted to WHO z-scores. Associations were examined using linear mixed-effects models adjusting for key maternal and infant covariates. Higher milk IL-10 was associated with lower weight-for-age and weight-for-length at 9 months and lower length-for-age at 3 and 12 months. Higher IFN-γ was associated with lower weight-for-length at 9 months. IL-6 and IL-8 showed age-related variation but no associations at individual timepoints. Breast milk IL-10 showed time-dependent associations with infant growth across multiple indicators throughout the first year, with similar age-related variation observed for some pro-inflammatory cytokines. These findings suggest that non-nutritive bioactive components of breast milk, and how their effects change across infant development, may contribute to early growth faltering in low-resource settings. Breast milk IL-10 showed consistent time-dependent associations with infant growth indicators from 3 to 12 months. Higher milk IL-10 was associated with poorer weight and length outcomes, while pro-inflammatory cytokines showed limited associations at individual timepoints. Adds to limited longitudinal evidence examining how milk cytokine-growth associations shift across infancy. Findings suggest that non-nutritive bioactive components of breast milk, and how their effects change across infant development, may contribute to growth faltering beyond nutritional factors alone. Further research integrating repeated cytokine sampling, multi-compartment immune profiling, and longitudinal growth assessment in similar settings could inform strategies to support optimal growth.