Zinc is an essential trace mineral in the human diet that is an important cofactor in the body’s natural antioxidant machinery. It is necessary for anti-inflammatory activity and proper immune function. Zinc deficiency is associated with malnutrition, whereas increased concentrations have been shown to improve inflammation and malnutrition in dialysis patients (Nutrients 2013;22;5:1456-1470).
In dialysis populations, dietary intake of zinc is often low (Perit Dial Int 2012;32:183-191; Am J Clin Nutr 2002;76:569-576). Hemodialysis (HD) patients exhibit reduced zinc levels when malnourished (Biol Trace Elem Res 2009;127:191-199), but the etiology of kidney disease affects the magnitude of zinc deficiency. Interestingly, one study demonstrated that zinc concentrations correlated with uric acid and parathyroid hormone (PTH) (Biol Trace Elem Res 2006;113:209-222).
Zinc is a necessary cofactor in superoxide dismutase, an enzyme necessary for protection against oxidative damage. Studies have found the activity of superoxide dismutase to be lower in dialysis patients (Nutr Hosp 2011;26:1456-1461).
Subsequently, multiple markers of inflammatory and oxidative stress have been shown coincide with low zinc, selenium, and iron levels (Perit Dial Int 2011;31:583-591). In a two-year prospective trial involving dialysis patients, low serum zinc was an independent predictor for increased risk of infection and overall mortality for those with a serum value less than the median of 72.2 μg/dL (Clin Nutr 2012;31:630-636).
A possible future evaluation parameter for zinc status in kidney disease populations involves metallotheionein (MT), a protein involved in heavy metal and free radical protection in renal tissues. In rodent studies, zinc depletion has been shown to decrease zinc and MT levels, whereas repletion upregulates MT concentration without changing zinc levels.
These results could indicate that MT is a more sensitive marker for changes in zinc concentration (J Trace Elem Biol 2009;23:176-182). Renal populations are at increased risk for accumulations of toxic metals, and thus the combined benefit of zinc on immune function and MT function may increase future focus on zinc supplementation for improved health outcomes.
Lead, aluminum protection
Zinc supplementation has been shown to decrease renal lead concentrations while upregulating MT concentrations. Lead is a renal toxicant, and zinc supplementation appears to offer protective effects against this metal (Biometals 2008;21:29-40). Other metals such as elevated plasma aluminum also present risk factors for oxidative stress in dialysis populations (Clin Biochem 2011;44:1309-1314).
In a recent study of zinc-deficient dialysis patients (Nutrients 2013;5:1456-1470), zinc supplementation significantly decreased levels of plasma aluminum and reactive oxygen species and increased plasma zinc and selenium concentrations.
Additionally, zinc supplementation was associated with elevated levels of superoxide dismutase, albumin, and hemoglobin, and reduced levels of the oxidative product malondialdehyde.