Nutrition in patients with Chronic Kidney Disease (CKD)

The goals of the diet in patients with CKD are three folds:

• 1. Decreased accumulation of nitrogen waste
• 2. Prevent malnutrition
• 3. Slow the progression of renal insufficiency

When to start the diet:

There is no data that indicate that protein restriction is beneficial in patients with GFR > 60 ml/min.

Diets used in CKD:

• 1. Protein 0.6 g/kg/day (2/3 of high biologic value)
• 2. Protein 0.3 g/kg/day plus a mixture of EAA or KA

Both diets should have a caloric intake of 35 kcal/kg/day

How to monitor compliance:

• 1. For protein use 24 hrs urine collections to measure UUN (urine urea nitrogen) and add that to NUN (non urea nitrogen) that is constant and independent of nitrogen intake and renal function (0.031 g N/kg).
• 2. For caloric intake: use dietary diaries or recalls (usually 3 days)

Formulas:

• BN = IN - U -NUN
• BN = 0 (stable)
• IN = U + 0.031 g N/kg
• When BUN is unchanging, then U = UUN and
• IN = UUN + 0.031 g N/kg

  Handbook Nutrition and the Kidney. William E. Mitch and Saulo Klahr

Pathogenesis of malnutrition in CKD:

• 1. Anorexia
• 2. Lack of understanding and poor motivation
• 3. Lack of family and social support
• 4. Intercurrent illness
• 5. Economic problems
• 6. Metabolic acidosis: insulin resistance. Stimulates protein and amino-acid catabolism (activates adenosine triphosphate-dependent ubiquitin-proteosome that participate in the proteolytic pathway in skeletal muscle)

A high number of patients with CKD are malnourished. Malnutrition usually develops during the course of the renal insufficiency and is associated with poor outcomes. Low protein and caloric intake is an important cause of malnutrition in patients approaching ESRD. The spontaneous dietary protein intake in these patients seems to parallel the progression of their chronic renal failure.

We need to analyze the following points:

• 1. Markers of Protein-Energy Malnutrition (PEM)
• We use the same measurements than in ESRD patients including: serum albumin, serum prealbumin, serum cholesterol, serum bicarbonate and serum transferring levels. We also use anthropometry, edema free weight, body mass index and Subjective Global Assessment SGA). The recommendation (K/DOQI) is to use these markers in a complementary fashion to optimize assessment of the CKD patient and tailor specific interventions.
• 2. When does PEM develop during the course of CKD.
• 3. If we intervene, are we able to modify the nutritional status of the CKD patients?

There are several points that have already been established:

• 1. PEM develops during the course of chronic kidney disease.
• 2. Malnutrition is associated with worse outcomes in CKD. This is evident after the patients start dialysis.
• 3. Low protein and caloric intake is an important cause of malnutrition in CKD. There are multiple factors but this seems to be the most important.
• 4. The level of dietary intake of protein and calories is related to the level of GFR. What does occurred in CKD that made this association?
• 5. Serum albumin, serum total proteins, prealbumin, serum transferring, serum bicarbonate, serum cholesterol are lowered in patients with decreased GFR.
• 6. Body weight, body mass index, percentage of body fat and skin fold thickness are lower in patients with decreased GFR