What is this study about? This clinical trial is designed to learn how potassium from different types of food affects blood potassium levels and overall health in people with chronic kidney disease (CKD, stages 3B-5). People with CKD are often advised to avoid potassium-rich foods, even though fresh fruits and vegetables are important for good health. However, potassium in processed foods (such as packaged snacks and ready-made meals) may be absorbed differently than potassium from fresh foods. This study will compare minimally processed vs. ultra-processed foods to determine how different sources of potassium affect potassium levels and help create better dietary recommendations for people with CKD. What are the study goals? The study will answer: * Does potassium from fresh foods (like fruits and vegetables) affect blood potassium differently than potassium from processed foods? * How does dietary potassium impact potassium absorption and excretion in people with CKD? Researchers will compare the effects of four diets to understand how low and normal-potassium rich diets from fresh vs. processed foods influence: * Blood potassium levels * Body composition (muscle, fat, and fluid balance) * Vascular health What will participants do? Participants will follow four different 10-day diets over the course of the study. All food will be provided at no cost. These diets are: * Minimally processed with low-potassium content * Minimally processed with normal potassium content * Ultra-processed with with low-potassium content * Ultra-processed with normal potassium content There will be 16-day breaks (washout period) between diets where participants return to their normal eating habits. During the study, participants will: * Pick up prepared meals from the research center approximately 3 times per week. * Attend checkups for weight, blood pressure, and blood tests. * Provide urine samples to track potassium levels. * Wear a comfortable, cuff-free blood pressure monitor at home. * Keep a study journal to track diet, medications, and symptoms. * Complete questionnaires about diet satisfaction and health changes.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
48
A diet restricted in potassium, primarily composed of industrially processed foods such as packaged snacks and processed meals.
A diet restricted in naturally occurring potassium, primarily composed of fresh fruits, vegetables, whole grains, and other minimally processed foods.
A diet with normal potassium content, primarily composed of fresh fruits, vegetables, whole grains, and other minimally processed foods, rich in naturally occurring potassium, following a Mediterranean-style pattern.
A diet with normal potassium content, primarily composed of industrially processed foods such as packaged snacks and processed meals
Fasting Serum Potassium Levels (mmol/L)
This measure assesses the concentration of potassium in participants' blood after fasting overnight. Normal potassium levels typically range from 3.5 to 5.0 mmol/L.
Time frame: Days 10, 36, 62, and 88.
Postprandial Whole-Blood Potassium Response (mmol/L)
This measure examines changes in blood potassium levels after a standardized test meal. Blood samples are collected before the meal (baseline) and at regular intervals (15, 30, 60, 90, 120, 150, and 180 minutes) to calculate the area under the curve (AUC), which reflects the total potassium response over time.
Time frame: 15, 30, 60, 90, 120, 150, 180 minutes post-meal at days 10, 36, 62, and 88.
Potassium Bioavailability
Potassium bioavailability is assessed by measuring the potassium content in 24-hour urine samples. This provides insights into how much potassium from the diet is absorbed and how much is excreted by the body.
Time frame: Days 7-9, 33-35, 59-61, 85-87.
Body Composition (kg)
This measure estimates participants' fat mass and fat-free mass. Body composition is assessed using bioelectrical impedance analysis, which uses safe, low-level electrical currents to estimate tissue and fluid distribution. Results are reported in kilograms (kg).
Time frame: Baseline and days 10, 36, 62, and 88.
Body water (L)
This measure evaluates fluid status, i which plays a role in potassium handling. Body water is estimated using bioelectrical impedance analysis, which uses safe, low-level electrical currents to estimate tissue and fluid distribution. Results are reported in liters for total, extracellular, and intracellular water.
Time frame: Baseline and days 10, 36, 62, and 88.
24h blood pressure (mmHg)
Systolic and diastolic blood pressure will be monitored for 24h.
Time frame: Days 8-10, 34-36, 60-62, and 86-88.
Dietary Satisfaction Questionnaire
Self-administered questionnaire to provide feedback on the palatability, variety, and overall acceptability of the study-provided diets.
Time frame: Days 10, 36, 62, and 88.
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