Abstract
BACKGROUND: Vitamin A and vitamin D(3) 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 D(3), and their combination on child growth. METHODS: Randomized controlled trials (RCTs) that evaluated the effects of vitamin A, vitamin D(3), 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 (I(2)) statistic. RESULTS: A total of 12 RCTs involving 6,340 children were included. Vitamin D(3) supplementation alone had no significant effect on height-for-age Z-score (HAZ) (Z=0.43, P=0.67) or weight-for-height Z-score WHZ (Z=0.52, P=0.61), but was associated with a modest yet statistically significant improvement in weight-for-age Z-score (WAZ) (Z=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 D(3) showed a small but significant improvement in WAZ (Z=2.16, P=0.03), but no consistent effects on HAZ or WHZ. Substantial heterogeneity was observed in the combined group (I(2)>70%), attributable to variability in supplement formulations, dosages, and study populations. CONCLUSIONS: Neither vitamin A nor vitamin D(3) 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.