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Zinc is a component or activator of many enzymes, especially enzymes participating in biosynthesis processes of nucleic acids and proteins. Thus the role of that microelement in the development of children is very important. The paper discusses clinical pictures of both mild and acute zinc deficiencies. Since the biological availability of zinc is much greater from mother's milk than from cow milk, thus during discontinuation of breast feeding the possibility is to be considered of occurrence of zinc deficiency.

The group of children infested with Giardia intestinalis consisted of 52 children aged from 3 to 10 years. The infestation was diagnosed on the basis of duodenal contents examination. The control group comprised 50 children in whom no infestation with intestinal parasites was found. Mean age of children in both groups was not different. Disturbances were found in zinc metabolism in children with Giardia intestinalis infestation. Mean serum zinc concentration in those children was 58% of serum zinc concentration in children in the control group. Similarly, zinc concentration in the erythrocytes of children in the infested group was lower and was 64% of the concentration in children in the control group. Elimination of zinc with urine in infested children was lower than in the control group, and was 36% of the level in non-infested children. Mean concentrations of serum zinc carriers, total protein, albumin fraction and transferrin were not differing between both studied group of children. Also the concentration of picolinic acid--a zinc absorption factor in the gastrointestinal tract--in duodenal contents was similar in both groups. The above mentioned results show that in children infested with Giardia intestinalis a decrease occurs of zinc absorption from the gastrointestinal tract which causes zinc deficiencies in the those children.

The influence of silicon treatment on the levels of trace elements zinc (Zn), copper (Cu), and iron (Fe) in serum and tissues was studied in rats. The concentrations of silicon, iron, and zinc were estimated in samples of sera and tissues of rats receiving per os a soluble, inorganic silicon compound--sodium metasilicate nonahydrate (Na2SiO3.9H2O), dissolved in the drinking water. An increase of copper concentrations in liver and aortic walls in the experimental group was observed, with simultaneous reduction of zinc amounts in serum and all the tissue samples in the course of the experiment. The iron concentrations in the analyzed samples did not show any significant changes between both groups. The silicon levels in serum and in all the examined tissues were significantly higher in the tested group. The results provide evidence for the silicon interaction with copper and zinc, which could result in a number of metabolic process modifications, antiatheromatous activity among them.

A review of the results published up to now of the determinations of serum zinc and copper levels showed that the criteria of selection of the groups of healthy subjects were lacking precision and rather arbitrary. The authors determined serum concentrations in 112 of healthy subjects fulfilling the individual criteria. No significant differences were found between the concentrations of these metals in the serum in this group of subjects and the mean concentration of these metals reported in the investigations quoted in the available literature. Serum copper concentration in patients was significantly higher than in healthy controls, while serum zinc concentration in the patients was not significantly different from that determined in healthy subjects.

Earlier investigators have demonstrated in animal studies interrelationships between mineral elements. Serum zinc, magnesium and copper were monitored over a two year period in 120 women between the ages of 40 and 55 years. One group (65 women) was supplemented with calcium, the other served as a control. We concluded that calcium supplementation at a level of 1,500 mg Ca mainly does not affect serum zinc, magnesium and copper, however, serum copper concentration is elevated in women taking medication for hypertension.

Studies of zinc and copper contents of breast milk were performed in 34 mothers during their lactation period until 5 days postpartum. They experienced no problems during pregnancy and delivery. All women had full term healthy infants, 22 were multiparous and 12 primiparous. The highest zinc concentration was found in the colostrum, and subsequently the concentration declined. Copper content was stable during the 5 days of lactation. Significantly lower zinc concentration and higher copper concentration were found in the serum of lactating women 3 days post partum, when compared with non-lactating women. Factors including lactation history, age of lactating women, serum levels of zinc and copper did not affect the contents of these trace minerals in breast milk.