Eighteen RCTs were included (n=11,180 reported in the text, but n=10,683 reported in table one, sample size ranged from 50 to 2,002). Allocation sequence concealment, randomisation, blinding and rates of follow-up were adequate in most studies. ITT analysis was used in only four studies.
Compared to placebo, use of zinc was associated with a significant reduction in diarrhoea duration (days) (WMD -0.69, 95% CI -0.97 to -0.40, I2=78%; n=5,643 infants, 13 RCTs; no evidence of publication bias) and risk for diarrhoea lasting longer than seven days (RR 0.71, 95% CI 0.53 to 0.96; n=5,769 infants, eight RCTs).
Compared to placebo, use of zinc was not associated with a significant reduction in stool volume (three RCTs) and stool frequency (stools/per day) (three RCTs).
Compared to control agent, use of zinc was associated with a significant increase in risk of vomiting (RR 1.22, 95% CI 1.05 to 1.43; n=3,156, five RCTs).
Subgroup analysis: Zinc supplementation had a greater effect on the duration of diarrhoea in malnourished patients (mean difference, MD -1.23, 95% CI -1.45 to -1.01, I2=60%; n=373, three RCTs) than in groups without severe malnutrition (MD -0.70, 95% CI -0.90 to -0.49, I2=19%; n=2,665, eight RCTs) or with no malnutrition at all (MD -0.65, 95% CI -1.29 to -0.01; n=280, one RCT).