Plasma Zinc Concentration Increases Within 2 Weeks in Healthy Senegalese Men Given Liquid Supplemental Zinc, but Not Zinc-fortified Wheat Bread

The responsiveness of plasma zinc concentration to zinc fortification is uncertain. Our objective in this study was to determine whether plasma zinc concentration changes in response to consuming zinc-fortified foods or liquid zinc supplements. We conducted a 4-wk double-blind, randomized trial among 132 healthy Senegalese men ≥ 18 y. Participants received 1 of 4 interventions: 1) (control) 200 g/d of wheat bread fortified with iron and folic acid, but not zinc, and a liquid multivitamin supplement without zinc between meals; 2) (zinc supplement) the same bread and the same multivitamin supplement with 15 mg zinc as ZnSO(4) added; 3) (moderate zinc fortification) the same bread cofortified with 7.5 mg zinc as ZnO and the same multivitamin supplement without zinc; or 4) (high zinc fortification) the same bread cofortified with 15 mg zinc as ZnO and the same multivitamin supplement without zinc. Fasting blood samples were collected twice at baseline and at d 15 and 29 of the intervention. There was no significant interaction between group and study day (P = 0.11). However, at d 15, the mean change in plasma zinc concentration in the zinc-supplemented group was greater than in the placebo and fortification groups ( 0.72 μmol/L vs. -0.09 to 0.03 μmol/L; P = 0.05). At d 29 there were no significant group-wise differences. Across all time points, the zinc-supplemented group was the only group where plasma zinc concentration increased from baseline (P = 0.006). These results suggest that plasma zinc concentration may not be a sufficiently sensitive indicator to evaluate short-term responses to zinc fortification.