Effects of iron and zinc supplementation in Indonesian infants on micronutrient status and growth.

Randomized, double-blind, placebo-controlled community trial in generally healthy, predominantly breastfed infants in rural West Java, Indonesia. Infants were about 4.2 months old at enrollment, and the setting was malaria-free rural Bogor District.

Infants received iron syrup 10 mg/d, zinc syrup 10 mg/d, or iron plus zinc syrup providing 10 mg/d of each supplement, administered orally 5 days per week for 6 months. The trial compared these active regimens with placebo; the iron and zinc salts were sulfate forms, and the combined arm used a 1:1 weight ratio.

Iron and zinc supplementation improved micronutrient status and reduced anemia, but none of the regimens improved growth. At 6 months, the iron group had higher hemoglobin and ferritin and lower anemia than the iron plus zinc group (hemoglobin 115 ± 10 g/L, anemia 28%, ferritin 36.8 [19.1-61.2] g/L, iron deficiency anemia 3%), while the iron plus zinc group still showed benefit (hemoglobin 110 ± 11 g/L, anemia 46%, ferritin 26.6 [16.9-41.7] g/L, iron deficiency anemia 8%). Zinc supplementation increased plasma zinc concentrations, and the iron, zinc, and iron plus zinc groups had plasma zinc values of 13.5 [11.4-15.3], 16.1 [13.4-20.3], and 15.0 [13.2-18.4] mol/L, respectively. No differences were seen for HAZ, WAZ, WHZ, or IGF-1, and the authors concluded that combined iron and zinc can safely address micronutrient deficiencies without improving growth.

Follow-up was limited to 6 months, and completion was lower in the iron plus zinc arm (78 of 120 randomized). The main benefits were biochemical rather than growth outcomes, and the findings come from a specific rural, predominantly breastfed infant population, which may limit generalizability.