Table 9  Efficacy of zinc in preventing respiratory illnesses in childhood.
Study  Author  Country  Study Population  Dosage  Results
Effect of zinc supplementation between 1 and 6 months of life on growth and morbidity of Bangladeshi infants in urban slums.  Osendarp et al., 2002 [269]  Bangladesh  300 infants from Dhaka slum area, from 4 weeks to 24 weeks of age  5 mg/day for 20 weeks  Reduced incidence of ALRI and greater weight gains.
Effect of zinc supplementation started during diarrhea on morbidity and mortality in Bangladeshi children: community randomised trial.  Baqui et al., 2002 [270]  Bangladesh  8070 children  20 mg/day for 14 days in case of diarrhea episodes  Reduced incidence of diarrhea and ALRI.
Simultaneous weekly supplementation of iron and zinc is associated with lower morbidity due to diarrhea and acute lower respiratory infection in Bangladeshi infants.  Baqui et al., 2003 [271]  Bangladesh  799 infants  Different micronutrient formulations, some including zinc 20 mg weekly for 6 months  Lower risk of severe ALRI in the group receiving iron + zinc.
Effect of weekly zinc supplements on incidence of pneumonia and diarrhea in children younger than 2 years in an urban, low-income population in Bangladesh: randomised controlled trial.  Brooks et al., 2005 [272]  Bangladesh  1621 children aged 60 days to 12 months  70 mg weekly for 12 months  Reduced pneumonia incidence and mortality.
The prophylactic and therapeutic effectiveness of zinc sulphate on common cold in children.  Kurugol et al., 2006 [273]  Turkey  200 children  15 mg/day for 7 months, increased to 30 mg/day during colds  Significantly lower mean number of colds and duration of symptoms.
Zinc and iron supplementation and malaria, diarrhea, and respiratory infections in children in the Peruvian Amazon.  Richard et al., 2006 [274]  Perù  855 children  Iron, zinc (20 mg/day), or iron + zinc for 7 months  No statistically significant effect on incidence of respiratory infections.
A double-blind, randomized, clinical trial of the effect of vitamin A and zinc supplementation on diarrhea and respiratory tract infections in children in Mexico City, Mexico.  Long et al., 2006 [275]  Mexico  736 children living in a peri-urban area  Vitamin A vs. 20 mg zinc daily vs. vitamin A + zinc vs. placebo for 12 months  No effect on the incidence of respiratory infections.
Zinc or multiple micronutrient supplementation to reduce diarrhea and respiratory disease in South African children: a randomized controlled trial.  Luabeya et al., 2007 [276]  South Africa  Over 370 children from a rural community  Vitamin A vs. zinc 10 mg/day + vitamin A vs. a multi micronutrients supplement, from 6 to 24 months of age  No reduction in diarrhea and respiratory morbidity.
Effect of zinc supplementation on mortality in children aged 1–48 months: a community-based randomised placebo-controlled trial.  Sazawal et al., 2007 [277]  Zanzibar  42,546 children  10 mg/day (5 mg in children younger than 12 months) until 48 months of age  Non-significant reduction in the relative risk of all-cause mortality.
Adding zinc to supplemental iron and folic acid does not affect mortality and severe morbidity in young children.  Bhandari et al., 2007 [278]  India  94,359 children  10 mg daily for 12 months  No significant difference in death and hospitalization rates.
Effect of daily zinc supplementation on child mortality in southern nepal: a community-based, cluster randomised, placebo-controlled trial.  Tielsch et al., 2007 [279]  Nepal  Over 40,000 children  zinc 10 mg/day vs. other supplements vs. placebo for 12 months  Not significantly different mortality rate sand frequency of respiratory infections.
Zinc supplementation for prevention of acute respiratory infections in infants: a randomized controlled trial.  Malik et al., 2014 [280]  India  272 children with acute respiratory infections  20 mg/day for 2 weeks  Decrease in duration of the episode, lower frequency of future ALRIs.
Occurrence of infections in schoolchildren subsequent to supplementation with vitamin D-calcium or zinc: a randomized, double-blind, placebo-controlled trial.  Mandlink et al., 2020 [281]  India  435 schoolchildren  (Children in the zinc arm)10 mg/day for 7 months  No significant reduction in the occurrence of infections.
ALRI, acute lower respiratory tract infection.