Interrelationships of key variables of human zinc homeostasis: relevance to dietary zinc requirements.

Currently, estimates of human zinc requirements depend primarily on a factorial approach. The availability of tracer techniques employing zinc stable isotopes has facilitated the acquisition of data on major variables of zinc homeostasis in addition to those that can be measured with careful metabolic balance techniques. These data have promising potential to facilitate and improve the factorial approach. The thesis proposed in this paper is that realistic estimations of dietary zinc requirements by a factorial approach require attention to the dynamic interrelationships between major variables of zinc homeostasis. This applies especially to the positive relationship between endogenous fecal zinc and total absorbed zinc, which is the essential starting point in estimating physiologic and, from there, dietary requirements.