Q) In my admitting orders for a CKD patient, I wrote for a “renal diet.” However, the nephrology practitioners changed it to a DASH diet. What is the difference? Why would they not want a “renal diet”?
The answer to this question is: It depends—on the patient, his/her comorbidities, and the need for dialysis treatments (and if so, what type he/she is receiving). Renal diet is a general term used to refer to medical nutrition therapy (MNT) given to a patient with CKD. Each of the five stages of CKD has its own specific MNT requirements.
The MNT for CKD patients often involves modification of the following nutrients: protein, sodium, potassium, phosphorus, and sometimes fluid. The complexity of this therapy often confuses health care professionals when a CKD patient is admitted to the hospital. Let’s examine each nutrient modification to understand optimal nutrition for CKD patients.
Protein. As kidneys fail to excrete urea, protein metabolism is compromised. Thus, in CKD stages 1 and 2, the general recommendations for protein intake are 0.8 to 1.4 g/kg/d. As a patient progresses into CKD stages 3 and 4, these recommendations decrease to 0.6 to 0.8 g/kg/d. In addition, the Kidney Disease Outcomes Quality Initiative (KDOQI) and the Academy of Nutrition and Dietetics recommend that at least 50% of that protein intake be of high biological value (eg, foods of animal origin, soy proteins, dairy, legumes, and nuts and nut butters). 2
Why the wide range in protein intake? Needs vary depending on the patient’s comorbidities and nutritional status. Patients with greater need (eg, documented malnutrition, infections, or wounds) will require more protein than those without documented catabolic stress. Additionally, protein needs are based on weight, making it crucial to obtain an accurate weight. When managing a very overweight or underweight patient, an appropriate standard body weight must be calculated. This assessment should be done by a registered dietitian (RD).
Also, renal replacement therapies, once introduced, sharply increase protein needs. Hemodialysis (HD) can account for free amino acid losses of 5 to 20 g per treatment. Peritoneal dialysis (PD) can result in albumin losses of 5 to 15 g/d. 2 As a result, protein needs in HD and PD patients are about 1.2 g/kg/d of standard body weight. It has been reported that 30% to 50% of patients are not consuming these amounts, placing them at risk for malnutrition and a higher incidence of morbidity and mortality. 2
Sodium. In CKD stages 1 to 4, dietary sodium intake should be less than 2,400 mg/d. The Dietary Approaches to Stop Hypertension (DASH) diet and a Mediterranean diet have been associated with reduced risk for decline in glomerular filtration rate (GFR) and better blood pressure control. 3 Both of these diets can be employed, especially in the beginning stages of CKD. But as CKD progresses and urine output declines, recommendations for sodium intake for both HD and PD patients decrease to 2,000 mg/d. In an anuric patient, 2,000 mg/d is the maximum. 2
Potassium. As kidney function declines, potassium retention occurs. In CKD stages 1 to 4, potassium restriction is not employed unless the serum level rises above normal. 2 The addition of an ACE inhibitor or an angiotensin II receptor blocker to the medication regimen necessitates close monitoring of potassium levels. Potassium allowance for HD varies according to the patient’s urine output and can range from 2 to 4 g/d. PD patients generally can tolerate 3 to 4 g/d of potassium without becoming hyperkalemic, as potassium is well cleared with PD. 2