Interactions of micronutrients can affect absorption and bioavailability of other nutrients by a number of mechanisms. In aqueous solutions, and at higher uptake levels, competition between elements with similar chemical characteristics and uptake process can take place. The consequences of these interactions may depend on the relative concentrations of the nutrients. In this work, we measure the effects of increasing concentrations of iron, zinc, and copper on iron and copper uptake in Caco-2 cells. Intracellular Fe or Cu levels were affected by incubating with increased concentrations of metals. However, when the cells already had different intracellular metal concentration, the uptake of Fe or Cu was nor affected. In competition studies, we showed that Cu and Zn inhibited Fe uptake, and while Fe inhibited Cu uptake, Zn did not. When the three metals were given together (1:1:1 ratio), Fe or Cu uptake was inhibited approximately 40%. These results point to a potential risk in the absorption and bioavailability of these minerals by the presence of other minerals in the diet. This aspect must be considered in food supplementation and fortification programs.

Changes in growth, body composition, and zinc indexes were evaluated after 25 wk in a double-blind zinc-supplementation study of 162 periurban Guatemalan children aged 81.5 ± 7.0 mo (x̄ ± SD). Children receiving the zinc supplement (10 mg Zn/d as amino acid chelate) for 90.1 ± 9.2 d had higher mean fasting plasma zinc (16.2 ± 2.9 vs 14.9 ± 2.1 umol/L, P < 0.01), a greater increase in median triceps skinfold Z score (0.50 vs 0.38, P < 0.05), and a smaller deficit in median midarm circumference (MAC) Z score (−0.03 vs −0.20, P < 0.05) compared with the placebo group. Initial hair zinc classified as < 1.68 and > 1.68 umol/g was the only laboratory variable that explained some of the variance in final Z scores of midarm-muscle area (P < 0.05) and MAC (P < 0.01). Children responded to the zinc supplement with changes in indexes of body composition rather than growth.