Objective: To demonstrate that a potassium-rich diet, including the use of SZC as potential rescue treatment (in case of hyperkalemia), does not result in an unacceptable rise in plasma potassium (i.e. max rise of 0.5 mmol/L and no hyperkalemia). Study

Design: Investigator initiated, single center, cross-over randomized clinical trial with non-inferiority design (14 weeks, 2 groups: regular diets vs. diet with potassium rich fruits and vegetables with sodium zirconium cyclosilicate if necessary) Study population: Outpatients ( age ≥ 18 years ) with chronic kidney disease stage IIIb/IV and use of inhibitor of the renin-angiotensin system (RASi). Intervention: Addition of fruit- and vegetables that contain 40 mmol of potassium on top of regular diet. Addition of SZC after 1 week in case hyperkaliemia develops (serum potassium \> 5,5 mmol/L). Weekly measurement of plasma potassium and dose adjustment of SZC if needed