Definition

Chronic Kidney Disease (CKD) is defined as the presence of kidney damage (typically indicated by albuminuria of ≥30 mg/day or equivalent markers such as Cystatin C or Beta-2-microglobulin) or decreased kidney function (estimated glomerular filtration rate [eGFR] ¹. CKD is associated with an increased risk of cardiovascular disease, infections, malignancies, and higher mortality rates.
Assessment of the severity (staging) of chronic kidney disease is based on the KDIGO guidelines (Kidney Disease Improving Guidelines) ¹.

GFR = Glomerular Filtration Rate

Impact on Nutritional Status

Patients with CKD are at a high risk of malnutrition due to reduced appetite, decreased food intake, and gastrointestinal uremic side effects. These are further exacerbated by uremia-associated factors (nausea, vomiting), chronic inflammation, metabolic acidosis, hypermetabolism, hormonal changes, and potential comorbidities. A U.S. study demonstrated that in older adults (≥60 years), a decrease in eGFR to  <30 ml/min/1.73 m² was associated with malnutrition (Odds Ratio [OR] 3.6), independent of the overall health status ².

Nutrient needs for patients with chronic kidney disease. Adjustments are necessary for malnourished patients, physical activity, and patient age. The weight used is Adjusted Body Weight (ADJ) if BMI is ≥28; otherwise, pre-hospitalization body weight is used.  
BW = Body Weight; d = Day 

Goals of Nutritional Therapy

• Maintain/improve nutritional status and body function.
• Prevent malnutrition and nutrient deficiencies.
• Reduce acidosis.
• Prevent osteopenia, osteoporosis, and atherosclerosis.
• Delay the progression of kidney function decline. ⁵

To detect malnutrition early, a Nutritional Risk Screening should be conducted at least twice a year.

Energy and protein needs should, whenever possible, be met through oral nutrition. If less than 75% of the requirements are met using fortified foods, snacks, or oral supplements, enteral nutrition should be introduced as a supplement after 5 days. Complementary parenteral nutrition is indicated if less than 75% of needs are met through oral and/or enteral nutrition.

Oral Nutrition

A moderate protein restriction of 0.6-0.8 g/kg body weight per day is recommended for stable patients without malnutrition. For diabetic patients, a slightly higher intake of 0.8-0.9 g protein per kg body weight is suggested to achieve better glycemic control ⁴. The extent of phosphorus and potassium restriction should be tailored based on serum levels and in consultation with the treating medical specialist or managed with medication (e.g., phosphate and potassium binders). Overall acid intake should be reduced, for example, by including fiber-rich foods (such as fruits, vegetables, and whole grains), which can reduce the formation of uremic toxins and positively impact inflammation ¹⁰.

CKD-specific oral supplements often contain reduced amounts of protein, potassium, and phosphorus ⁵. A reduction in protein intake to below 0.6 g/kg body weight is not common practice in Switzerland and requires close monitoring of nutritional status and amino acid supplementation ⁴.

Practical Tips for Restrictions (if indicated):

• Protein: Include a protein source in each main meal, combining animal and plant-based proteins. Adjust protein intake to individual needs (consider portion sizes, replace protein-rich foods with lower-protein alternatives, and focus on a good protein/phosphorus ratio). Limit to a maximum of 3 portions of dairy products and 1 portion of meat, fish, eggs, legumes, or tofu per day.
• Phosphate: Avoid foods with artificial phosphate additives and high phosphate content, especially processed foods with the following additives: [E 338, E 339, E 340, E 341, E 343, E 442, E 450, E 451, E 452, E 541, E 1410, E 1413, E 1414, E 1442]. Note: Organic meat products do not contain phosphate additives ¹¹.
• Potassium: Reduce potassium-rich foods and opt for lower-potassium alternatives: Limit potatoes to 120 g, a maximum of three times per week. Replace whole grain products (such as whole grain pasta, bread, rice) with white flour products and white rice. Avoid dried products (such as dried fruits, beans, mushrooms). Pay attention to preparation methods, portion size, and consumption frequency.
• Salt: Use salt moderately during preparation and avoid additional salting at the table. Increase the use of herbs, garlic, and onions for seasoning. Note: Spice mixes, bouillon, liquid seasonings, soy sauce, and ready-made sauces often have a high salt content. Favor cooking methods like steaming or braising instead of boiling in salted water. Consume salty foods like processed foods, canned goods, salty snacks, and charcuterie in moderation. Caution: Some diet and herbal salts contain potassium chloride instead of sodium chloride. These are suitable for patients with high blood pressure but not for those with kidney disease.
• Acid Reduction: Moderate consumption of animal products. Prefer plant-based protein sources. Include fiber-rich foods like fruits, vegetables, and whole grains (note potassium content).

Enteral and Parenteral Nutrition

Enteral and/or parenteral nutrition is generally required only for patients with an additional acute illness that increases nutrient needs, which cannot be adequately met through oral or enteral intake ¹².

Monitoring

• Monitoring serum concentrations of proteins, glucose, phosphate, potassium, sodium, parathyroid hormone (PTH), bicarbonate, and Vitamin D3:
  • Prevent malnutrition due to protein restriction.
  • Manage hyperglycemia caused by peripheral insulin resistance and hepatic gluconeogenesis through appropriate dietary intake ¹³.
  • Estimate salt intake via 24-hour urine collection: Sodium in mmol / 17.1 mmol = salt intake in grams (e.g., 50 mmol Na+ ≈ 3 g NaCl, 100 mmol ≈ 6 g NaCl, 150 mmol ≈ 9 g NaCl). Assumption: Patient in steady state, all sodium in urine originates from dietary salt.
  • Prevent hydrogen ion (H⁺) retention and subsequent metabolic acidosis. Substitute bicarbonate (HCO3⁻) if serum levels are
  • Substitute calcitriol (1,25-OH-Vitamin D) for patients with CKD Stages 4 and 5 (KDIGO) as kidney-derived calcitriol synthesis decreases with eGFR
• If anemia is present:
  • Exclude and treat iron deficiency. If unresolved, administer erythropoiesis-stimulating agents (ESA). Anemia in CKD is typically normocytic and normochromic, caused by reduced erythropoietin production and shortened red blood cell lifespan, particularly with eGFR ¹⁴.
• Evaluate nutritional therapy measures three times in the first year after initiation, then annually.

Adapted from ¹⁵

Medications/Supplements

• Phosphate Binders: Calcium carbonate, Calcium acetate, Alucol®, Phosphonorm®, Renagel®, Renvela®, Fosrenol®, Velphoro®. Timing and dosage should align with the phosphate content of meals.
• Potassium Ion Exchangers: Resonium®, Veltassa® (initial prescription by cardiologist or nephrologist only). Regular use as prescribed is crucial and does not require administration with meals.
• Vitamin D Analogues: ViDe-Drops, Rocaltrol®, Zemplar®.
• Calcimimetics: Cinacalcet (Mimpara®), Etelcalcetide (Parsabiv®).
• Other Vitamin Supplements: Dialvit®.