Zinc supplementation has proven beneficial in the treatment of acute child
diarrhea and appears to enhance linear growth. There is a theoretical risk of
anemia in
zinc-supplemented children due to inhibited
iron transport via decreased
copper absorption. Although many
zinc supplementation trials have included hematological measures, the potential effect of
zinc on these outcomes has not been quantitatively evaluated in a comprehensive review. We performed a systematic review of randomized trials that examined the effect of
zinc supplementation on
hemoglobin concentrations in apparently healthy children ages 0-15 y and conducted a random effects meta-analysis of weighted mean differences (WMD) of change in
hemoglobin concentrations before and after supplementation. Twenty-one randomized, controlled trials representing 3869 participants were included in the meta-analysis. The
duration of treatment ranged from 4 to 15 mo; doses were typically 10-20 mg/d.
Zinc supplementation did not affect changes in
hemoglobin concentrations (pooled WMD: 0.8 g/L; 95% CI: -0.6, 2.2; P = 0.27). There was no evidence for effect modification by age,
zinc dosage,
duration of treatment, type of control, baseline
hemoglobin status, geographical or healthcare setting, or quality of the studies. These results suggest that
zinc supplementation at doses typically used in randomized trials is a safe intervention with regards to
hemoglobin concentrations. Some benefits might exist among children with severe
anemia or
zinc deficiency, which warrant further evaluation.