Objective: To test the effect of zinc supplementation on the nutritional status of patients on continuous ambulatory peritoneal dialysis (CAPD).
Material and methods: Double-blinded randomized controlled clinical trial. Twenty-five patients with end stage renal disease (ESRD) on CAPD program, from 16 to 60 years old were studied. Two weeks before the beginning of the study all the drugs with a known effect on zinc absorption were withdrawn. Patients were randomly allocated into one of two groups. The control group consisted of 12 patients receiving placebo, and the intervention group of 13 patients receiving 100 mg/day of elemental zinc for 3 months. The diet was individually adjusted to 35 kcal/kg/day, and 1.5 g/day of proteins. Subjective global assessment (SGA), anthropometric measurements, electric bioimpedanciometry, measurements of albumin, prealbumin, and transferrin, and evaluation of energy, proteins, carbohydrates, and lipids consumption were done to classify the nutritional status at the beginning and at the end of the study. Therapeutic compliance was assessed by measuring plasma zinc levels and by capsule counting.
Results: There were no statistically significant differences between groups regarding age, gender, time on CAPD, and ESRD causes. The proportion of patients classified as well nourished, or with mild or moderate malnutrition by SGA did not show significant differences between the group receiving Zn supplementation and the group receiving placebo. Anthropometric measurements and body composition assessed by bioelectric impedance were similar in the two groups. In the control group, serum levels of albumin (3,621 +/- 838 vs. 3,068 +/- 842 mg/dL), prealbumin (49 +/- 14 vs. 44 +/- 12 mg/dL), and transferrin (238 +/- 94 vs. 195 +/- 79 mg/dL) decreased significantly at the end of the follow-up period respect to the baseline values (p < 0.05). In the intervention group albumin (3,320 +/- 910 vs. 2,696 +/- 964 mg/dL), prealbumin (43 +/- 9 vs. 38 +/- 8 mg/dL), and transferrin (236 +/- 99 vs. 193 +/- 66 mg/dL) also decreased significantly (p < 0.05). In the control group baseline zinc level was low (60 +/- 5 micrograms/dL) and remained stable along the follow-up period, while in the intervention group it increased from 52 +/- 5 (baseline) to 92 +/- 9 micrograms/dL (end of the follow-up, p < 0.05).
Conclusions: Zinc supplementation did not improve the nutritional status in patients on CAPD.