Is There a Relationship between Diet and Nutrition Status in Continuous Ambulatory Peritoneal Dialysis Patients?

Abstract

Early work in continuous ambulatory peritoneal dialysis (CAPD) patients established nutrition recommendations of 1.2 g protein and 35 cal daily per kilogram body weight (1). However, studies measuring dietary intake have shown that many patients fail to achieve these recommendations (2). More recent studies have demonstrated that some CAPD patients maintain good nutrition status (assessed using the same criteria as in the present study) with much lower intakes—around 0.8 g protein daily per kilogram body weight (3). It is widely accepted that many CAPD patients are malnourished (4). This acceptance is due to the belief that low serum albumin (SA) concentrations reflect poor nutrition status. However, no direct correlation between SA and nutrition status has been established (5). Also, in CAPD, a number of other factors—such as protein loss in dialysate, the effect of chronic or repeated infections, and suboptimal clearance of uremic toxins—may contribute to low SA (6). It is possible only to state that low SA in CAPD patients is generally associated with poor nutrition and is a marker for poor outcomes in terms of morbidity and mortality. Malnutrition in CAPD is recognized as a multi-factorial problem (7). One aspect that may be important, and that has not been widely studied, is the provision of protein-sparing calories. A supply of additional calories from fat and carbohydrate would (or should) ensure that ingested protein is not used as an energy source. The present study aimed to establish the extent to which the diets of CAPD patients in our unit fall below the recommended levels, and to observe, without using SA as a marker, if any patient maintained good nutrition status despite a poor intake. We also aimed to assess whether SA concentrations reflected either dietary intake or anthropometric estimates of nutrition status. Serum leptin concentrations have previously been shown to be elevated in renal failure. Leptin is postulated to contribute to anorexia (8,9). We also aimed to assess any possible contribution of leptin to nutrition status in our patients. Well-nourished CAPD patients are likely to achieve good outcomes on dialysis. Once given suitable initial dietary advice, they may not need frequent dietetic follow-up. Identifying patients with a good intake would allow dietitians to target patients more likely to benefit from input and advice, thus making optimal use of dietetic resources.