Contrary to many dietary interventions in chronically ill patients, which usually take a “one-way” direction (ie, weight loss in obesity or low fat intake in many dyslipidemiae), the nutritional support towards kidney patients has a changeable face. Indeed, it is a diet that will mostly stay isocaloric when its protein content will regularly change over time in response to the different stages of the renal failure.
Because there is no protein storage in adults, every gram of protein absorbed above the daily requirement at the early stage of renal failure will increase urea generation and, hence, blood urea nitrogen. For this reason at least, protein should be limited to the optimal amount, eg, 0.7 to 0.8 g/kg ideal body weight (IBW)/day, a safety level obtained from clinical research that includes two standard deviations above the individual mean, ensuring that 96% of patients will stay in neutral protein balance. However, all these trials have been performed with a sufficient energy provision, and these protein requirements are adequate only if patients eat at least 35 kcal/kg/day. Thus, when the kidney disease progresses to the stage of chronic insufficiency, patients should reduce their intake by about 40% from an occidental diet, which brings about 1.3 to 1.4 g protein/kg/day, and keep a sufficient energy intake. This challenge is unique in the field of nutrition and requires an adequately trained staff. It should be noted that this stage of renal disease is probably the worst followed, because many chronic renal failure (CRF) patients will not see a renal dietitian before entering dialysis.
Then, when the dialysis treatment becomes necessary (ESRD stage), a complete reversal occurs. Indeed, due to enhanced protein losses through the dialysis membrane, excess catabolism secondary to the hemodialysis (HD) session, or spontaneous peritoneal losses during peritoneal dialysis (PD), patients’ protein intake has to be strongly increased to 1.2 in MHD and 1.3 g protein/kg/day in PD patients. A qualitative change in food selection therefore has to be done because energy intake must remain constant. In addition, intake of specific compounds such as phosphorus and potassium becomes of major importance. Increasing protein intake and limiting phosphorus is again very peculiar, and this can only be clarified after specific training of the dietitian and the patient. Thus, the dietitian will appear as a counselor and will have an important psychological impact in helping for taste identification and best food selection during this difficult transition period.
For some patients, a third episode may occur because they will receive a kidney transplantation. Indeed, after diuresis restoration, subnormal urea clearance, and electrolyte normalization, almost none of the former diet care plan will apply. Patients will be encouraged to drink much more than they used to do for many months or years, and improve their anabolism against high doses of corticosteroids by strongly increasing their protein intake for a couple of months. Then, if renal function stabilizes around 50 mL/min, to avoid progression of chronic rejection, a limitation of protein intake should again be proposed, similar to the pre-ESRD phase. However, at this stage, usually patients eat more, are more hypertensive as a consequence of cyclosporine treatment, and may have drug-induced diabetes and dyslipidemia. All these symptoms will become specific and subtle dietary targets, particularly those of cardiovascular domain.
Thus, all their life long, patients with chronic kidney disease will have to face frequent, complex, and sometimes difficult diet pattern modifications to preserve renal function and body composition, and to be protected against treatment side effects. Who else better than the renal dietitian can rehabilitate these different aspects?
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