Efficacy of combined iron and zinc supplementation on micronutrient status and growth in Vietnamese infants

Objective: To evaluate the effect of combined iron - zinc supplementation on micronutrient status, growth and morbidity. Design: Randomized, double-masked, placebo-controlled supplementation trial. Setting: Rural district of Que Vo, in the Red River Delta in Vietnam. Subjects: A total of 915 breast-fed infants aged 4 - 7 months were included and 784 completed the study. Interventions: The Fe-group received daily and for a 6-month period 10 mg of iron, the Zn-group 10 mg zinc, the Fe - Zn group 10 mg iron + 10 mg zinc and the placebo group a placebo. Hemoglobin (Hb), serum ferritin ( SF) and zinc (SZn), and anthropometry were measured before and at the end of the intervention. Morbidity was recorded daily. Results: Changes of Hb and SF were higher in both Fe and Fe+Zn groups ( respectively 22.6 and 20.6 g/l for Hb; 36.0 and 24.8 mg/l for SF) compared to Zn and placebo groups ( Hb: 6.4 and 9.8 g/l; SF: - 18.2 and - 16.9 mg/l, P<0.0001). SZn increased more in Zn group (10.3 mu mol/l) than in Fe+Zn group (8.0 mu mol/l, P = 0.03) and more in these groups compared to Fe and placebo groups (1.6 and 1.2 mu mol/l, P<0.0001). Weight gain was higher in the Zn group. No significant effects of supplementations on growth in length or morbidity. Conclusions: Combined iron - zinc supplementation had a positive effect on iron and zinc status in infants. However, the positive effect of zinc alone on SZn and weight would indicate a negative interaction of iron when added to zinc supplements.