Background: Micronutrient deficiencies remain common in preschool children in developing countries. Interventions focus on single micronutrients and often lack effectiveness. Weekly instead of daily supplementation may improve effectiveness. Objective: The efficacy of weekly and daily supplementation in reducing anemia prevalence and in improving the zinc, vitamin A, and growth status of 6-24-mo-old Vietnamese children was investigated. Design: In this double-blind, placebo-controlled trial, the daily group (n = 55) received 8 mg elemental Fe (as iron sulfate), 5 mg elemental Zn (as zinc sulfate), 333 g retinol, and 20 mg vitamin C 5 d/wk for 3 mo. The weekly group (n = 54) received 20 mg Fe, 17 mg Zn, 1700 g retinol, and 20 mg vitamin C once a week. A third group (n = 54) received a placebo only. Venous blood samples were collected at the start and end of the supplementation period and anthropometric measurements were taken at the start and 3 mo after the end of supplementation. Results: At baseline, 45.6% of subjects had hemoglobin concentrations < 110 g/L, 36.3% had zinc concentrations < 10.71 mol/L, and 45.6% had retinol concentrations < 0.70 mol/L. Hemoglobin, retinol, and zinc concentrations of both the weekly and daily groups increased similarly compared with the placebo group (P < 0.001). There was no significant difference in growth between the supplemented groups and the placebo group. However, the height-for-age of subjects stunted at baseline increased with z scores of 0.48 (P < 0.001) and 0.37 (P < 0.001) for the daily and weekly groups, respectively. Conclusions: Weekly and daily supplementation improved hemoglobin, zinc, and retinol concentrations similarly. Neither intervention affected growth of the overall population, but growth of children stunted at baseline was improved through both types of supplementation.Am J Clin Nutr 1999;69:80-6.

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