Effects of vitamin A and vitamin D<sub>3</sub> supplementation on child growth and development in low- and middle-income countries: a systematic review and meta-analysis.

Abstract

<h4>Background</h4>Vitamin A and vitamin D₃ are essential micronutrients for child growth and development. However, previous studies have shown inconsistent results with respect to their individual and combined effects on anthropometric outcomes. We aimed to conduct a systematic review and meta-analysis to assess the impact of vitamin A, vitamin D₃, and their combination on child growth.<h4>Methods</h4>Randomized controlled trials (RCTs) that evaluated the effects of vitamin A, vitamin D₃, or their combination on growth in children aged 0-14 years (primary population: children aged 0-5 years; secondary exploratory analyses: 0-14 years) were included. Data were pooled using fixed- or random-effects models, and heterogeneity was assessed with the I-squared (I²) statistic.<h4>Results</h4>A total of 12 RCTs involving 6,340 children were included. Vitamin D₃ supplementation alone had no significant effect on height-for-age <i>Z</i>-score (HAZ) (<i>Z</i>=0.43, P=0.67) or weight-for-height Z-score WHZ (<i>Z</i>=0.52, P=0.61), but was associated with a modest yet statistically significant improvement in weight-for-age <i>Z</i>-score (WAZ) (<i>Z</i>=2.72, P=0.007), though the clinical relevance of this finding remains uncertain. Vitamin A supplementation alone had no significant impact on HAZ, WAZ, or WHZ. Among children aged 0-5 years, combined supplementation of vitamins A and D₃ showed a small but significant improvement in WAZ (<i>Z</i>=2.16, P=0.03), but no consistent effects on HAZ or WHZ. Substantial heterogeneity was observed in the combined group (I²>70%), attributable to variability in supplement formulations, dosages, and study populations.<h4>Conclusions</h4>Neither vitamin A nor vitamin D₃ alone significantly improved child growth. Combined supplementation may provide modest benefits in weight gain but is insufficient to address linear growth or acute malnutrition. Future strategies should adopt multi-nutrient approaches and consider contextual factors such as infection control, dietary diversity, and socioeconomic conditions.