Zinc supplementation in chronic kidney disease of unknown aetiology in Sri Lanka: a pilot study. (ZisCKDu-P)

Introduction: It was hypothesized that the antioxidant properties of zinc retard the progression of chronic kidney disease of unknown etiology in the North Central Province of Sri Lanka. Methods: The pilot study was a randomized, placebo-controlled, single blinded, parallel group, single-center clinical trial with two arms (Z and P) and a 1:1 allocation ratio. Participants in group Z (n=20) received 60 mg of elemental zinc daily, in the form of zinc sulfate, and group P (n=21) received a starch tablet per day. Clinical, hematological parameters and kidney function were measured at the baseline and following three months of the intervention. Results: A total of 86 CKDu patients were screened; only 35 males and 6 females were selected. Mean age and estimated glomerular filtration rate of the study population were 51.2±6.2 years and 38.9±8.8 mL/min/1.73 m2 respectively. At the end of three months there was non-significant increase in urine protein creatinine ratio (Z arm: 65±54 vs. 82± 86 mg/mmol; P=0.46, P arm: 72.4±113 vs. 120± 209 mg/mmol; P=0.36) and non-significant decline in estimated glomerular filtration rate (Z arm: 40.9±10.4 vs. 39.7±9.2 mL/min/1.73 m2; P=0.31, P arm: 37.1±6.8 vs. 36.4±10 mL/min/1.73m2; P=0.31) in both groups. Body mass index was significantly reduced (23±4 vs. 22.7± 3.9 kg/m2; P=0.01) and diastolic blood pressure was significantly increased (78±6 vs. 86±10 mmHg; P=0.001) in the placebo arm. Haemoglobin levelshowed a decline in the study group; 0.33±1 g/dl, while there was an increase in the placebo group, 0.34±0.7 g/dl, (P=0.02). There were no major side effects. Conclusions: The change of urine protein: creatinine ratio and estimated glomerular filtration rate did not show a significant difference between the two groups. A future trial should test effectiveness of same dose of zinc for a similar duration of time in a larger sample. Extended follow-up of the study subjects for one year after the intervention would be useful to assess the long-term effects of zinc on kidney function and side effects.