Timing of Complementary Feeding and Infant Growth Trajectories in Prospective Cohort Studies: A Systematized Review and Analysis of Socioecological Variation.

This systematized review examines how the timing of complementary feeding affects infant growth across 22 prospective cohort studies. The research shows that starting complementary feeding before 6 months has different effects depending on context: it is associated with slower growth in lower-resource settings but faster growth in wealthier contexts. The review highlights that local norms and caregivers' perceptions of child growth strongly influence when families introduce complementary foods, and that reverse causality (slower-growing infants being fed earlier) may explain some findings.

Key points

• Earlier complementary feeding was generally associated with slower growth in lower resource populations
• Earlier complementary feeding was associated with more rapid growth in higher resource contexts
• Growth trajectories after earlier CF largely tracked prior growth, suggesting reverse causality
• Local norms and caregivers' perceptions of growth are key factors impacting feeding decisions but were rarely explicitly modeled in studies
• The relationship between CF timing and growth outcomes is context-dependent and influenced by socioecological factors

Limitations

This is a systematized review rather than a meta-analysis, so it does not provide quantitative synthesis of effects. The review notes that local norms and caregiver perceptions were often discussed but not formally measured or analyzed in the included studies, limiting understanding of these mechanisms.