Fresh vs. processed: which potassium is safer for kidney patients?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Participants aged ≥18 years living with stage 3B-5 CKD (estimated glomerular filtration rate ≥ 15 mL/min/1.73m2) on conservative kidney management (not on dialysis). * Able and willing to follow a controlled feeding regimen, attend in-person visits, provide informed consent, and comply with study procedures. Exclusion Criteria: General * Pregnant or lactating women. * Transitioning transgender individuals. * Individuals with strict dietary preferences (e.g., vegetarians, vegans) or allergies/intolerance that would preclude participation in the diet phases. Kidney Function * Foreseen start of renal replacement therapy within the next 6 months. * Acute kidney injury in the past 3 months. * 2-year Kidney Failure Risk Equation \> 40%. * Preemptive kidney transplant planned within the next 6 months. * History of kidney transplant. * Active glomerulonephritis. Comorbidities * Acute myocardial infarction or stroke within the past 6 months. * Active cancer. * Ileostomy, short bowel syndrome or inflammatory bowel disease. * Body mass index \< 18.5 or ≥ 35. * New York Heart Association Class III or IV congestive heart failure. * History of ventricular arrhythmia. * Major surgery within the past 3 months. * Active autoimmune disease. * Glycated hemoglobin \> 10% within the past 3 months. * Gastroparesis. * Chronic nausea and vomiting. * Intensive care unit admission within the past 3 months. * Significant psychiatric disease. * Uncontrolled blood pressure (above 160/100). Current Use of Medications/Supplements * Immunosuppressives. * Potassium binders. * Lithium. * Motility agents. * More than 2 medications that inhibit renal potassium excretion (e.g., angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, mineralocorticoid receptor antagonists). * Supplements known to influence potassium levels. Potassium-Related Conditions * Potassium \> 5.5 mmol/L in more than 3 episodes within the past year. * Participants with genetic issues affecting potassium handling (e.g. Barter and Liddle syndrome) or other unique health conditions that could interfere with potassium handling. Intervention-related Conditions * Fluid volume status or hypertension being actively managed. Other Factors * Documented non-adherence to medications or other therapeutic measures. * Use of tube feeding or parenteral nutrition.