In chronic renal failure, attention should be paid to restricting protein intake, as this can slow the progression of the disease. In addition, reduced protein (egg white) intake ameliorates potential complications. Protein restriction should be performed in conjunction with a general diet aimed at achieving optimal nutritional status. In addition to protein restriction, attention should be paid to reduced cholesterol intake and normal blood lipid levels. Nutritional therapy should be started at the stage of full compensation.
Stage of full compensation
The smallest functional units of the kidney, the nephrons, are still able to cope with the normal metabolic loads due to hyperfiltration, which means that there is no increase in urinary substances. Daily protein intake: reduction to 0.8 grams per kilogram of body weight (g/kg), taking into account an intake of essential amino acids that meets requirements and an adequate energy intake.
Stage of compensated retention
In the compensated retention stage, creatinine and urea levels (serum creatinine 3-6 mg/dl) are elevated. Daily protein intake: intake of 0.5 to 0.6 g protein/kg, taking into account an adequate supply of essential amino acids to meet requirements and adequate energy intake.
Progressive renal failure
In the advanced stage of renal failure, creatinine and urea levels (serum creatinine >6 mg/dl) are severely elevated. Daily protein intake: intake of 0.35 to 0.4 g/kg, taking into account a requirement-meeting supply of essential amino acids and adequate energy intake. A moderate reduction in protein intake to 0.6 to 0.8 g/kg can already be achieved by avoiding meat. Several dietary forms are available for implementing a strictly low-protein diet, for example “potato-egg diet” or “Swedish diet”. The potato-egg diet contains the highest quality protein due to the combination. The so-called Swedish diet represents a not so strict food selection, so that the menu can be more varied. However, in this diet the essential amino acids are supplied in insufficient quantity. It is therefore necessary that essential amino acids be supplemented as dietary foods.
Dialysis Therapy
Dialysis treatment leads to an increased need for vital substances, which is essentially due to the dialysis itself. Water-soluble vitamins, electrolytes and amino acids are particularly affected. The diet of dialysis patients should therefore be rich in protein, i.e. contain 1.2 to 1.5 g protein/kg.
Nutritional and vital substance recommendations
When protein intake is restricted, vitamin B6 (10-50 mg/d) and folic acid ( 1-5 mg/d) should be substituted. Administration of all water-soluble vitamins has been shown to be effective for this purpose. Furthermore, iron substitution may also be necessary. In uremia, vitamin A levels are elevated, so administration is contraindicated. Zinc should only be administered in cases of complaints such as hypogeusia (reduced taste sensation) or impotence. Vitamin D should be substituted in advanced chronic renal failure in the form of 1,25-dihydroxy vitamin D3 if secondary hyperparathyroidism cannot be controlled by low phosphate diet and calcium-containing phosphate binders. Early supplementation of vitamin D may also be necessary to compensate for declining synthesis of active vitamin D. This measure serves to prevent or treat renal osteopathy. Furthermore, alkaline minerals (potassium, calcium) – dose-dependent on the serum concentrations of the minerals – and bicarbonate should be supplied to buffer metabolic acidosis. Likewise, trace elements and must be taken as needed. In addition to the supply of high-quality proteins and vital substances, attention must be paid to an adequate energy supply. Particular importance should be attached to an adequate fat intake with plenty of monounsaturated fatty acids (e.g. olive oil or rapeseed oil) and polyunsaturated fatty acids (e.g. corn germ oil or safflower oil). Scientific studies demonstrate the benefits of dietary intake of omega-3 fatty acids (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) in chronic renal insufficiency.
