Feasibility, descriptive single arm open-label interventional trial lasting 6 weeks. The study will recruit 36 CKD patients at the outpatient clinic with: age between 18 to 85 years; glomerular filtration rate \< 29 ml/min/1.73 m2 and not on dialysis; serum K \> 5.1 mmol/L or in previous use of sodium polystyrene sulfonate (SPS) to decrease serum K levels, and who develops hyperkalemia after SPS is ceased. Patients with serum K \> 6.5 mmol/ and those likely to start dialysis within 2 months, with inflammatory bowel syndrome or with a history of hypokalemia (\<3.0 mmol/L) will not be included. Primary end points will be changes in patient satisfaction with treatment, patient symptom list, and intake of energy and protein before and after the stabilization and healthy diet phase. Secondary outcomes will include changes in quality of life, obstipation and circulating gut microbiota-related uremic toxins. Intervention: In the first 3 weeks, representing stabilization phase, SZC will be prescribed to normalize plasma potassium to 3.5 to 5.0 mml/L, and a diet with energy 25-35 kcal/kg/day and protein 0.6 to 0.8 g/kg/day and with low K content will be prescribed by a renal dietitian. At the end of the first 3 weeks, the patients will be instructed to keep the diet with same content of energy and initiate a healthy diet containing 3700 to 4000 mg/potassium for 3 weeks (healthy diet phase). In order to increase adherence, a food basket containing fruits, vegetables, whole grains, nuts, white meat, fish and eggs in amounts adequate for the patient and the family will be provided. Serum K will be monitored to promote serum K between 3.5 to 5.0 mmol/L and adjustments in the dose of SZC will be performed according to the drug label. Blood measurements, questionnaires related to quality of life and intestinal obstipation and measurements of nutritional intake will be performed in the beginning and at the end of the stabilization phase and again in the beginning and end of the healthy diet phase. Additionally, during stabilization and healthy diet phases, serum K will be measured every 72 hours until serum K is normalized and after that, once per week.
