The Effect of Zinc Supplementation on Biomarkers of Zinc, Iron, and Copper Status in School Children in Guatemal

Preventive zinc supplementation is beneficial for children with high risk of zinc deficiency, but its adverse effect on biomarkers of iron and copper status is still a great concern.;A randomized controlled trial of zinc supplementation was conducted in five public schools in a low-income urban area in Guatemala City from January to October 2006. Eligible children aged 6-11 years were randomly allocated to receive daily chewable tablets of 10 mg zinc oxide or placebo for six months. All the children concurrently received fortified milk (daily 200 ml of whole milk, containing 1.6 mg zinc and 1.1 mg iron). Participants (n= 720) had high risk of zinc deficiency (21.6% low serum zinc and 39.4% low dietary zinc intakes). At baseline, serum ferritin and copper concentrations correlated with serum C-reactive protein concentration (p 0.05). Serum ferritin and copper concentrations were associated with high CRP levels, starting from the CRP >0.5 mg/L level (p <0.001). Among zinc biomarkers (i.e., serum zinc, ALP, and albumin), only serum zinc concentration was associated with dietary zinc intakes both before and after 6-month interventions (p ≤0.06). All significant associations and agreements were weak (r ≤0.21, kappa ≤0.12). At six-month follow-up, compared to placebo, zinc supplementation induced higher serum zinc concentration and ALP activity (p ≤0.03), but had no effect on iron or copper biomarkers (p >0.05). In the placebo group, fortified milk program improved serum zinc concentration and ALP activity (p <0.0001), but decreased serum ferritin and copper concentrations (p<0.0001).;Overall, serum CRP was associated with serum ferritin and copper, but not with serum zinc. Serum zinc concentration was consistently associated with dietary zinc intakes. Daily zinc supplementation increased zinc status but did not induce changes in iron and copper status. The fortified milk improved zinc biomarkers but decreased iron and copper biomarkers. This is the first study that observed a positive association between serum CRP and copper concentrations. The study confirms the beneficial impact of zinc supplementation on zinc status and its safety on iron and copper status.