Assessment of techniques for determining human zinc requirements

Human zinc requirements have been assessed from balance studies, from measurements of tissue endogenous losses, and from the functional response to a marginal zinc intake. The results of those studies show that human beings adapt to reductions in zinc intake by reducing urinary and fecal zinc excretion. Some preliminary evidence suggests that tissue zinc status influences endogenous losses and, therefore, the dietary need. Individuals in good status may require higher amounts of zinc in their diets than individuals in poor status. Determination of the functional response to a marginal zinc intake is difficult because of the lack of a specific, sensitive indicator of zinc status. Presently, no good method for assessment of human zinc requirements exists.