Nutraceutical: Zinc

Indication: Prevention of Childhood Morbidity/Mortality

Source: Cochrane Database of Systematic Reviews, May 2014

Research: Zinc deficiency is prevalent in low- and middle-income countries, and contributes to significant diarrhea-, pneumonia- and malaria-related morbidity and mortality among young children. Zinc deficiency also impairs growth. This study sought to assess the effects of zinc supplementation in children aged six months to 12 years of age. Between December 2012 and January 2013, researchers searched for randomized controlled trials of preventative zinc supplementation in children aged six months to 12 years compared with no intervention, a placebo, or a waiting list control. They excluded hospitalized children and children with chronic diseases or conditions. They also excluded food fortification or intake, sprinkles and therapeutic interventions.

Results: Researchers included 80 randomized controlled trials with 205,401 eligible participants. The risk ratio (RR) for all-cause mortality was compatible with a reduction and a small increased risk of death with zinc supplementation (RR 0.95, 95% confidence interval (CI) 0.86 to 1.05, 14 studies, high-quality evidence), and also for cause-specific mortality due to diarrhea (RR 0.95, 95% CI 0.69 to 1.31, four studies, moderate-quality evidence), lower respiratory tract infection (LRTI) (RR 0.86, 95% CI 0.64 to 1.15, three studies, moderate-quality evidence) or malaria (RR 0.90, 95% CI 0.77 to 1.06, two studies, moderate-quality evidence).

Supplementation reduced diarrhea morbidity, including the incidence of all-cause diarrhea (RR 0.87, 95% CI 0.85 to 0.89, 26 studies, moderate-quality evidence), but the results for LRTI and malaria were imprecise: LRTI (RR 1, 95% CI 0.94 to 1.07, 12 studies, moderate-quality evidence); malaria (RR 1.05, 95% 0.95 to 1.15, four studies, moderate-quality evidence).

There was moderate-quality evidence of a small improvement in height with supplementation but the size of this effect might not be clinically important. There was a medium to large positive effect on zinc status.

Supplementation was associated with an increase in the number of participants with at least one vomiting episode (RR 1.29, 95% CI 1.14 to 1.46, five studies, high-quality evidence). Researchers found no clear evidence of benefit or harm of supplementation with regard to hemoglobin or iron status. Supplementation had a negative effect on copper status.

Study authors concluded the benefits of preventative zinc supplementation outweigh the harms in areas where the risk of zinc deficiency is relatively high. Further research should determine optimal intervention characteristics such as dose.