Nutrition in Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD)

Acute kidney injury (AKI) refers to a range of injuries to the kidneys including those that may lead to kidney failure [1]. More specifically, AKI is characterized by a rapid decrease in kidney function that is associated with abnormal changes in the production and breakdown of carbohydrates, fats, and proteins [2-5]. The gradual progression of AKI can lead to chronic kidney disease (CKD) [4]. Individuals with CKD have an increased risk for multiple conditions and death due to the development of protein-energy wasting (PEW) and malnutrition [5].

Protein, Energy, and Muscle Wasting in CKD

Individuals with CKD experience numerous health problems such as: the breakdown of skeletal muscle proteins; an increased demand for amino acids; inflammation; nitrogen, water, acid-base, and electrolyte imbalances; high blood sugar; and insulin resistance, which refers to the body’s inability to use insulin properly [2, 5].

In particular, the imbalance of protein production and breakdown leads to protein wasting, dramatic weight loss, and decreased muscle tissue (muscles waste away) [6]. Similarly, inflammation increases the body’s use of protein as well as fat stores for energy, which results in protein-energy wasting and additional weight loss [7]. Typically protein and caloric intake through the regular diet no longer meets the body’s demands and this worsens muscle wasting in individuals with CKD.

Protein and Micronutrient Demands

As kidney function continues to decrease, appetite decreases, PEW accelerates, and malnutrition develops. Individuals with advanced CKD also require dialysis, which involves filtering the blood in order to purify it. However, dialysis further contributes to poor nutrition by not only removing harmful substances from the blood, but also stripping the blood of proteins, amino acids, and other vital nutrients (e.g., blood sugar). This accelerates skeletal muscle loss and without proper nutrient (e.g., protein) supplementation the risk of serious complications increases [8].

Protein Requirements and Oral Nutritional Supplements

Previously, dietary protein restrictions were recommended during the early stages of pre-dialysis CKD, but over time research indicated that low protein diets heighten the risk of undernutrition and do not significantly delay the progression of CKD [9]. Therefore, more recent guidelines recommend controlled, moderate protein intake for those with pre-dialysis CKD, and the recommended protein intake slightly increases as CKD progresses to more advanced stages [9].

Supplementation with sodium, potassium, and phosphate is also vital for improving mineral, electrolyte, and fluid balance in individuals with CKD however, the intake must be controlled just as with protein, to prevent PEW [9].

The general recommendations are in the following ranges [9-14]:

Predialysis CKD stages 3-4:  
Protein intake 0.75g/kg/day to 1.0g/kg/day
Dialysis CKD stage 5:  
Protein intake 1.2g/kg/day to 1.5g/kg/day 
Dialysis CKD:  
Sodium less than 2,300mg/day
Potassium 3,800 mg/day (CKD-ideal body weight)
Phosphate 800-1000 mg/day

Accordingly, clinical studies show that oral nutritional supplements (ONS) that provide proteins, amino acids, etc., and energy in the form of calories, help improve body weight for individuals receiving maintenance dialysis, without negatively influencing electrolyte levels [15]. Another promising technique is intra-dialysis, parenteral nutrition which involves the administration of a nutritional liquid formula through an intravenous needle (IV) during dialysis to treat protein-calorie malnutrition [16].


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