Objectives: To assess the effect of zinc supplementation on growth and body composition among schoolchildren.
Design: Randomized, double-blind, placebo-controlled trial.
Setting and subjects: 313 rural Zimbabwean schoolchildren (144 boys and 169 girls, 11-17 y).
Interventions: Supplementation with zinc (30 or 50 mg) or placebo on schooldays for 12 months. Due to drought, a food programme was in operation during the last eight months of the study.
Variables: Weight, height, upper arm circumference, triceps skinfold thickness, and weight-for-age, height-for-age, weight-for-height, arm muscle-area-for-age and arm fat-area-for-age Z-scores.
Results: Significant effects on weight gain (0.51 vs 0.14 kg, P = 0.01), weight-for-age Z (-0.08 vs -0.14, P = 0.01) and arm muscle area-for-age Z-score (0.10 vs 0.01, P = 0.03) were seen over the first three months, whereas no effects were seen over the full 12 months.
Conclusions: Zinc deficiency impairing lean body mass and weight gain was documented. However, the effect of zinc seen over the first three months vanished during the last nine months when the food programme was in operation. Zinc deficiency may have persisted, but another nutrient may have become growth limiting during the last nine months.