Zinc is lost from the body primarily through the feces (Figure 1). Feces contain unabsorbed dietary zinc, zinc contained within intestinal epithelial cells that have been sloughed off, and endogenous zinc secretions into the gut from the pancreas, the gall bladder, and the cells lining the gastrointestinal tract. The endogenous secretions and the extent to which they are reabsorbed can be controlled and constitute an important homeostatic mechanism for regulating zinc status. Zinc losses in urine are relatively minor but do respond to extremes of intake to help maintain homeostasis. Shed skin cells, sweat, hair, menstrual blood, and semen are additional routes of loss.
appears to be necessary for normal zinc absorption. The zinc efflux protein ZnT-1 is found at the baso-lateral membrane and probably promotes the passage of zinc out of the intestine. Acrodermatitis entero-pathica can be treated with large doses of zinc, supporting the existence of paracellular transport at high intake levels. A large amount of zinc is secreted into the gut from the pancreas and intestine (Figure 1). Malabsorption syndromes can lead to a failure to reabsorb these endogenous secretions and, hence, to rapid loss of body zinc.
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