Dose-response trial of prophylactic zinc supplements, with or without copper, in young Ecuadorian children at risk of zinc deficiency.

Dose-response trial in Ecuadorian children 12 to 36 months old who were at risk of zinc deficiency and had low length-for-age. Four active intervention arms were studied: 3 mg Zn/d (n=124), 7 mg Zn/d (n=126), 10 mg Zn/d (n=126), and 10 mg Zn/d plus 0.5 mg Cu/d (n=128).

Children received oral zinc sulfate syrup for 6 months in one of three daily doses: 3 mg, 7 mg, or 10 mg zinc. A fourth active arm received 10 mg zinc plus 0.5 mg copper daily, also as oral syrup. The regimen was compared with placebo in the parent trial.

Daily zinc supplementation improved zinc status and reduced diarrhea, with the clearest benefit seen at 3 mg/d and 7 mg/d. Mean plasma zinc increased progressively with higher zinc doses (P 0.001), and diarrhea incidence was 21-42% lower in children receiving any zinc dose than in placebo (P 0.01 overall); the reductions were significant for 3 mg Zn/d (P 0.04) and 7 mg Zn/d (P 0.01). There were no significant differences in other morbidity symptoms or in growth across groups. Ten mg/d zinc did not produce adverse effects on copper or iron status or on lipoprotein concentrations, and adding copper did not create clear safety concerns.

The intervention lasted 6 months and enrolled a specific population of young Ecuadorian children with low length-for-age, which limits generalizability. Growth outcomes did not differ by group, and the available summary does not provide complete detail on the placebo arm or on long-term follow-up beyond the intervention period.