Moderator's View

Low-protein Diet in Chronic Kidney Disease

Effectiveness, Efficacy and Precision Nutritional Treatments in Nephrology

Carmine Zoccali; Francesca Mallamaci


Nephrol Dial Transplant. 2018;33(3):387-391. 

In This Article

Further Steps Towards Precision Nutritional Management in CKD Patients

Precision medicine aims at customizing treatments. Such a long-standing quest has stimulated the design of a new breed of clinical trials, i.e. trials that randomize patients after a run-in period where non-responders to treatment and those who develop side effects to the intervention being tested are excluded.[19] This design allows the assessment of interventions selectively in patients who show early positive responses and that tolerate the same interventions. In this respect, the trial by Garneata et al.[15] was the first dietary trial in CKD that by design randomized only patients who showed good compliance to a low-protein diet (0.6 g/kg/day) to then assess the efficacy of the key intervention (very low-protein diet and keto analogues) only in patients who were most likely to maintain this intervention during follow-up.

New trials focusing on compliant patients that tolerate the dietary intervention being tested and maintain a satisfactory nutritional status may project renal nutrition research into a new era of precision nephrology (Figure 1). On the other hand, the importance of surveillance of the nutritional status and protein-energy intake in patients on a low-protein diet cannot be overemphasized. In this regard, recent recommendations by the European Renal Association, European Dialysis and Transplantation Association (ERA-EDTA) working group on renal nutrition suggest that five (in Stage G3b) to eight (Stage G4) dietitian visits per year are needed to optimize surveillance.[20] In the same vein, the nutritional care process algorithm recommends a renal dietician visit every 1–3 months in Stages G3–4 CKD patients.[21] Although potentially cost effective,[22] such a degree of surveillance is a tantalizing organizational issue for most clinical settings. Hypothesizing an average number of five dietitian visits per year in the USA (Stage G3b–4 CKD patients, about 11 million people), such a degree of surveillance would demand 27.5 million/h/year of dietitian time (i.e. five 30-min visits per year per 11 million patients). Probably each dietitian could dedicate to patients' visits a maximum of ~1200 h/year. Therefore dietary counselling to CKD Stage G3b–4 patients would demand 22 916 full-time dietitians in the USA, which is ~26% of the registered dietitian workforce in the USA (the global workforce being 89 300 dietitians). The corresponding estimate in France (~1 400 000 Stage G3b–4 patients, 11 000 dietitians) is again 26%, i.e. about 2916 full-time dietitians. Considering the increased demand of counselling obese and diabetic patients, particularly in the USA, I believe that it is unrealistic to have about one-third of the whole workforce of dietitians entirely dedicated to the follow-up of CKD patients.

Figure 1.

Traditional trial comparing a hypothetical nutrition intervention with a control diet. In the new trial design, the run-in period can be extended to 3–6 months to identify and then exclude uncompliant patients and patients who develop early side effects, e.g. loss of appetite, weight loss and reduction in serum albumin.

It is well-known that in the USA renal dietitians do not follow the Kidney Disease Outcomes Quality Initiative guidelines for diet assessment because of time constraints.[23] In this scenario, surveillance efforts may perhaps be preferentially devoted to preselected patients, i.e. patients that maintain good compliance and show favourable time trends in the progression of CKD and metabolic control while less intensive surveillance could be dedicated to patients who are 'resistant' to educational efforts and show persisting uncompliance. These patients may be reallocated to a diet with a higher protein content, which poses a lower risk of malnutrition.[18] Telehealth[24] and low-cost educational instruments for patients and specific software facilitating self-management and compliance, including dietary treatment apps,[25] are being developed. Needless to say, before being introduced into clinical practice these treatment policies and new instruments of patient surveillance should be tested in appropriately designed trials based on sound clinical endpoints, including quality of life and treatment tolerance, as well as hard endpoints like kidney failure free survival time.