Daily zinc gave children small gains and more vomiting
Across 39 trials children on zinc had about 9% fewer bouts of diarrhoea and ended up very slightly taller. Vomiting rose about 29%, and chest infections did not budge.
What the study found
Zinc's gains in children are small and come with more vomiting
Across 39 trials, children on zinc had about 9% fewer bouts of diarrhoea, and across 74 trials they ended up very slightly taller. Chest infections did not budge, on high-certainty evidence. Vomiting rose by about 29%, the trade-off the benefits are usually quoted without.
The caveat · Height gain invisible in one child
The height gain is a standardised effect of 0.12, which is real across a population and invisible in any one child. The diarrhoea figure came from 19,468 children while the mortality analyses carried over 130,000 each, which is part of why the nulls in this review are the more certain results. The trials ran mostly in low- and middle-income countries where zinc shortage is common.