“…We found 23 studies [36,43,48,59,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88], with 35 comparisons, 14 of them comparing zinc alone to placebo, 17 of them comparing zinc in combination with iron to iron only and four of them comparing zinc and other micronutrients to other micronutrients. Sub-group analyses showed that if iron was part of the intervention, the effect of zinc on serum/plasma zinc concentrations was considerably lower (1.02 µmol/L, 95% CI 0.28, 1.76), compared to interventions delivering zinc alone (3.04 µmol/L, 95% CI 1.16, 4.92) and to interventions delivering zinc and other micronutrients, excluding iron (2.77 µmol/L, 95% CI 0.13, 5.42; Figure 2).…”