Amino acid and protein intake in RDT patients. A nutritional and biochemical analysis

In 40 unselected RDT patients (20 center and 20 home dialysis patients) the intake of nutrients was measured using the precise weighing method of Wirths [1969]. The protein intake was found to be 0.97 plus or minus 0.19 g/kg predialysis body weight, the calorie intake 32.3 plus or minus 6.4 cal/kg. Two thirds (0.65 plus or minus 0.15 g/kg) of the protein consisted of high biological value protein. Despite the fact that according to current recommendations the protein intake should have been adequate, signs of protein malnutrition were found. The mean serum concentrations of total protein, transferrin and valine and the ratio of essential amino acids to nonessential amino acids (EAA/NEAA) were significantly lower than in normal subjects and the glycine level was elevated. Histidine levels were normal indicating that the histidine intake measured at 1.75 plus or minus 0.47 g/day appeared adequate under these conditions. Phenylalanine levels were elevated indicating a blocking of 4-hydroxylase leading to low tyrosine levels. A possible reason for these findings may be that the protein requirements of the RDT patient over a long period of time are higher than those found experimentally in short term studies. An inadequate calorie intake could not be excluded. Additionally a dialysis dependent pathologic variation of the daily intake of nutrients may be responsible for the disturbed nutritional status. In connection with this, three distinct types of intake variation can be described: A stable type in which the variation in the daily protein and calorie intake does not differ by more than 20% from a daily mean value, an unstable type I with significantly lower intake on the day of dialysis and an unstable type II with a significantly higher intake on the day of dialysis. Signs of protein malnutrition occurred significantly more frequently in the unstable groups.