Update: Current international opinion is that daily protein intake should not be less than 0.6-0.8 g/ (kg?d) for affected patients even in stage 4-5 chronic kidney disease. Other elements still have value.
The global prevalence of end-stage renal disease has continued to increase in recent years. This is associated with an aging population, an increased incidence of diseases that can cause kidney damage (especially diabetes), and an increase in the availability of dialysis treatment. The cost of treating patients with end-stage renal disease is also increasing, which is undoubtedly a huge economic problem for a developing country like China in particular. In February 2004, a national expert group of nephrologists and diabetologists held the first meeting to develop the “Expert Consensus on Protein Nutrition Therapy in Chronic Kidney Disease” and revised it in March 2005, aiming to point out the prospect of protein-restricted diet for patients with chronic kidney disease (CKD) and to provide a reasonable clinical dietary treatment plan.
1. The significance of nutritional therapy for CKD
Protein-restricted diet is an important part of the treatment of CKD, especially chronic renal failure. In order to prevent malnutrition, it is recommended to supplement patients with compounded α2-keto acid or essential amino acid preparations when a low-protein diet, especially a very low-protein diet, is implemented. Studies have shown that supplementation with compounded α2-keto acids is more effective than essential amino acids in delaying the progression of renal damage. The benefits of low-protein diet with α2-keto acid supplementation include: (1) Reduction of azotemia and improvement of metabolic acidosis. (2) Replenish essential amino acids and improve protein metabolism. (3) Reducing insulin resistance and improving glucose metabolism. (4) Improving lipase activity, improving lipid metabolism. (5) Reduce high blood phosphorus, improve low blood calcium, and reduce secondary hyperparathyroidism. (6) Reduce protein urine excretion and slow down the progression of CKD.
2. Implementation plan of nutrition therapy
2.1 Pre-dialysis patients with non-diabetic nephropathy
2.1.1 Protein intake The recommended protein intake is 0.8 g/(kg?d) for CKD stage 1 [glomerular filtration rate (GFR) ≥90 ml/(min?1. 73m2)] and stage 2 [GFR 60-89 ml/(min?1. 73m2)] in principle. From stage 3 of CKD [GFR < 60 ml/(min?1. 73m2)], a low-protein diet should be started with a recommended protein intake of 0.6 g/(kg?d) and supplementation with a compounded α2-keto acid preparation of 0.12 g/(kg?d). If GFR is severely reduced [< 25 ml/(min?1.73m2)] and the patient tolerates more stringent protein restriction, the protein intake can be reduced to about 0.4 g/(kg?d) and supplemented with 0.20 g/(kg?d) of compounded α2-keto acid. Because of the calcium content of the compounded α2-keto acid preparation (50 mg of calcium per tablet), it is important to monitor blood calcium when taking larger doses, especially when taken in conjunction with active vitamin D, to prevent hypercalcemia. In a low protein diet, approximately 50% of the protein should be high biomass protein.
2. 1. 2 Caloric intake The caloric intake should be maintained at 30-35 kcal/(kg?d) on a low-protein diet.
2. 1. 3 Other nutrients Vitamins and folic acid should be adequately supplemented. In case of hyperphosphatemia, phosphorus intake should be limited to less than 800 mg/d (optimal intake is 500 mg/d).
2.2 Pre-dialysis diabetic nephropathy patients
The recommended protein intake is 0.8 g/(kg?d) from the onset of proteinuria. The recommended protein intake is 0.6 g/(kg?d) and may be supplemented with 0.12 g/(kg?d) of a compounded α2-keto acid preparation.
2. 2. 2 Caloric intake The caloric intake of patients on a low-protein diet should be similar to that of non-diabetic nephropathy patients as described above, except that obese type 2 diabetic patients should be appropriately restricted in calories (total caloric intake can be reduced by 250-500 kcal/d compared to the above recommendations) until they reach standard weight. Since protein intake (only about 10% of total calories) and fat intake (only about 30% of total calories) are restricted, the calorie deficit can only be supplemented by carbohydrates, and insulin should be injected to ensure carbohydrate utilization if necessary.
2. 2. 3 Other nutrients Same requirements as for non-diabetic nephropathy patients.
2. 3 Hemodialysis and peritoneal dialysis patients
The recommended protein intake for maintenance hemodialysis patients is 1.2 g/(kg?d), which should be increased to 1.3 g/(kg?d) when the patient has acute disease with high catabolic status; the recommended protein intake for maintenance peritoneal dialysis patients is 1.2-1.3 g/(kg?d). 50% of dietary protein should be high biomass protein. This can be supplemented with a compounded α2-keto acid preparation of 0.075-0.120 g/(kg?d).
2. 3. 2 Caloric intake The recommended caloric intake is 35 kcal/(kg?d), which can be reduced to 30-35 kcal/(kg?d) for people over 60 years old, with low activity level and good nutritional status. 2. 3. 3 Other nutrients
2. 3. 3 Other nutrients Patients should be provided with various vitamins, folic acid and iron at the same time.
3. Monitoring of patients on low-protein diet
The patient’s compliance and nutritional status must be closely monitored to prevent malnutrition during the implementation of low-protein diet therapy.
3. 1 Monitoring of compliance with diet therapy
The 24-h urinary urea excretion should be measured, and the 24-h peritoneal dialysis urea excretion should also be measured in patients on peritoneal dialysis, and then the protein equivalent of nitrogen appearance rate or protein equivalent of total nitrogen excretion (Protein Equivalent of Nitrogen Appearance Rate, PNA) or protein catabolic rate (PCR) should be calculated. In the case of nitrogen balance, the value should be equal to the protein intake.
3. 1. 2 Caloric intake monitoring The actual caloric intake of the patient is calculated based on the patient’s 3-d diet record.
3. 2 Assessment of the patient’s nutritional status Patients with CKD are prone to malnutrition from GFR < 60 ml/min, so the patient's nutritional status should be monitored from this point on. After the implementation of low protein diet, the patient should be monitored closely and regularly. The following methods should be applied to the patient's nutritional status, and then a comprehensive analysis should be performed to make an objective assessment of the patient's nutritional status.
3. 2. 1 Anthropometric measurements including body mass index, triceps skinfold thickness and upper arm muscle circumference.
3. 2. 2 Biochemical parameters including serum protein, transferrin, prealbumin and serum cholesterol.
3. 2. 3 Subjective comprehensive nutritional assessment (SGA)