Beneficial effects of zinc supplementation on head circumference of Nepalese infants and toddlers: a randomized controlled trial

BACKGROUND/OBJECTIVE: To assess the effects of micronutrient supplementation on head circumference of rural Nepali infants and children. SUBJECTS/METHODS: We used a randomized controlled trial to assess the effects of micronutrient supplementation on head circumference in 569 rural Nepali infants and children aged 4-17 months. Children were randomized to: (1) zinc, (2) iron-folic acid, (3) zinc plus iron-folic acid or (4) a placebo group. Data on head circumference were collected during five visits at similar to 3 month intervals over the course of a year. We calculated change in head circumference in treatment groups receiving zinc and iron comparing the first and fifth visits as well as used generalized estimating equations (GEE) to take advantage of data from all points in time. Models were adjusted for covariates unbalanced in the randomization and for baseline head circumference. RESULTS: Estimating differences in head circumference between baseline and visit 5, children in the zinc treatment group showed smaller decreases in head circumference z-score compared with placebo (adjusted beta=0.13, 95% confidence interval (CI): 0.03 to 0.23). Using GEE, zinc treatment was associated with 0.11 (95% CI: 0.05 to 0.17) decrease in the rate of decline in head circumference z-score across visits as compared with placebo. Iron-folic acid supplementation was not associated with head circumference z-scores when comparing visits 1 with 5 or including data across all visits in adjusted models. CONCLUSION: Our results suggest that zinc supplementation confers a beneficial effect on the rate of head growth in Nepali infants.