Zinc and Chronic Renal Disease

Abstract

SummaryHypozincemia is common in patients with hronic renal insufficiency, and in patients with ESRD treated with peritoneal and hemodialysis. The causes of the decreased plasma zinc concentration in these patients are not completely understood, but poor nutritional zinc intake, diets associated with attempts to prevent the progression of renal failure, prescribed mineral supplements and medications, hypoalbuminemia, diminished gastrointestinal zinc absorption, increased urinary zinc excretion and redistribution of zinc into the intracellular fluid may all affect extracellular fluid zinc concentration and total body zinc stores in patients with chronic renal insufficiency. Zinc intake is probably the most important determinant of total body zinc status and plasma zinc concentration in these patients. The extent of true zinc depletion in this population is unknown, but it is likely to be an important problem.Patients with ESRD treated with hemodialysis may have similar reasons for developing hypozincemia, although it is unlikely that urinary losses play an important role in the development of negative zinc balance in this group. Although there is little evidence that hemodialysis results in net zinc losses, treatment effects may result in the redistribution of zinc from the extracellular fluid, resulting in the development of hypozincemia. Because such patients appear to be susceptible to the development of negative zinc balance due to gastrointestinal zinc losses, it would seem that they require increased levels of zinc intake. The similarity of the symptoms of zinc deficiency and uremia have prompted several studies of the effects of zinc supplementation on taste acuity, sexual, immune and neurologic function in hemodialysis patients, with some positive results.Patients with ESRD treated with CAPD may have hypozincemia as well, for reasons similar to those suggested in patients treated with hemodialysis. De‐spite protein losses in the peritoneal dialysate, net influx of zinc occurs during peritoneal dialysis.Since zinc deficiency may mediate some symptoms of uremia in patients treated for ESRD, clinicians should consider measuring circulating zinc concentration and providing therapeutic supplementation with zinc salts to hypozincemic patients with abnormalities of taste, sexual and immune function. Studies which have demonstrated a beneficial effect of zinc supplementation have used daily doses of 50 mg of zinc, given as zinc acetate, zinc chloride, or zinc sulfate. Zinc sulfate ingestion has been associated with gastrointestinal side effects. Zinc chloride has been added to dialysate in chronic studies to achieve a final zinc concentration of 400 μg/L, with beneficial results. The proper route, amount and length of such therapies, however, are currently unknown. Whether one zinc compound has clinical advantages compared to others must also await con‐trolled clinical evaluation.