INTRODUCTION — Zinc is an essential trace element. Zinc intake is closely related to protein intake; as a result, it is an important component of nutritionally related morbidity worldwide. Symptoms attributable to severe zinc depletion include growth failure, primary hypogonadism, skin disease, impaired taste and smell, and impaired immunity and resistance to infection. Zinc supplementation in populations likely at risk for zinc deficiency appears to have beneficial effects on the incidence and outcome of serious childhood infectious diseases.
ZINC METABOLISM — Approximately 10 to 40 percent of dietary zinc is absorbed in the small bowel; absorption is inhibited by the presence of phytates and fiber in the diet that bind to zinc, as well as dietary iron and cadmium [1]. Nonetheless, a randomized trial showed that standard iron supplements did not significantly interfere with zinc absorption or reduce zinc levels in healthy breastfed infants [2]. Approximately 0.5 to 1.0 mg/day is secreted in the biliary tract and excreted in the stool.
Zinc circulates at a concentration of 70 to 120 mcg/dL with 60 percent loosely bound to albumin and 30 percent tightly bound to macroglobulin. Urinary excretion typically ranges from 0.5 to 0.8 mg/day. The primary stores of zinc include the liver and kidney. Most of the body zinc stores are intracellular where zinc is bound to metalloproteins