Nutritional Interventions in Chronic Kidney Disease

Lilian Cuppari

NUTRITIONAL INTERVENTION IN CHRONIC KIDNEY DISEASES

In serious chronic diseases such as chronic kidney disease (CKD) the nutritional condition has important impact on many outcomes. Protein-energy wasting (PEW) is highly prevalent in patients with advanced CKD and is strongly associated with morbidity and mortality, particularly in patients undergoing maintenance dialysis therapy. Conversely, overweight and obesity are also common nutritional abnormalities in CKD and may have undesirable effects, especially in earlier stages of CKD and transplant patients. Additionally, the development of several metabolic and hormonal disturbances, the presence of comorbidities, and the effect of renal replacement therapies make the nutritional interventions complex because multiple nutrients must be altered simultaneously. Therefore, a successful intervention depends not only on knowledge on the various nutrition-related aspects of the disease but also on the appropriate approaches to implement dietary plans that can be effectively followed by the patients.

This chapter addresses the main applicable clinical information regarding the nutritional status evaluation, dietary planning, and nutritional intervention for patients with CKD in different stages of the disease.

Assessment and Monitoring Nutritional Status

Assessing and monitoring the nutritional status of patients with CKD during every stage of the disease are critical to prevent, diagnose, and treat nutritional abnormalities. Assessment of nutritional status requires multiple different parameters because there is not a single measurement that provides unequivocal and complete diagnosis of the nutritional condition. Therefore, several methods have been proposed including those that are simple and readily available in the clinical practice and others that are expensive and sophisticated and usually used for research purposes. It is beyond the scope of this chapter to describe in detail each method, but instead this chapter provides a panel of methods that has been considered the most reliable by the majority of published clinical practice guidelines on nutrition in kidney disease. There is a consensus that the panel should include anthropometrics and biochemical measurements, subjective global assessment (SGA), and dietary intake evaluation.

Recently, the International Society of Renal Nutrition and Metabolism (ISRNM) organized an expert panel to re-examine the
terms and criteria used for the diagnosis of PEW. Table 18-1 shows the expert panel recommendations for four main and established categories to the diagnosis of PEW. At least three out of the four listed categories (and at least one test in each of the selected category) must be satisfied for the diagnosis of kidney disease-related PEW.

Table 18-1. Readily utilizable criteria for the clinical diagnosis of protein-energy wasting in acute kidney injury and chronic kidney disease

CRITERIA

Serum chemistry

Serum albumin <3.8 g per 100 mL (Bromocresol Green)^*

Serum prealbumin (transthyretin) <30 mg per 100 mL (for patients on maintenance dialysis only; levels may vary according to GFR level for patients with CKD stages 2-5)^*

Serum cholesterol <100 mg per 100 mL^*

Body mass

BMI <23 kg/m²^†

Unintentional weight loss over time: 5% over 3 months or 10% over 6 months

Total body fat percentage <10%

Muscle mass

Muscle wasting: reduced muscle mass 5% over 3 months or 10% over 6 months

Reduced mid-arm muscle circumference/area^‡ (reduction >10% in relation to 50th percentile of reference population)

Creatinine appearance^§

Dietary intake

Unintentional low DPI <0.8 g/kg/day for at least 2 months^¶ for dialysis patients or 0.6 g/kg/day for patients with CKD stages 2-5

Unintentional low DEI <25 kcal/kg/day for at least 2 months^¶

^*Not valid if low concentrations are because of abnormally great urinary or gastrointestinal protein losses, liver disease, or cholesterol-lowering medicines.

^†A lower BMI might be desirable for certain Asian populations; weight must be edema-free mass, for example, postdialysis dry weight.

^‡Measurement must be performed by a trained anthropometrist.

^§Creatinine appearance is influenced by both muscle and meat intake.^¶Can be assessed by dietary diaries and interviews, or protein intake by calculation of normalized protein equivalent of total nitrogen appearance (nPNA or nPCR) as determined by kinetic measurements.

AKI, acute kidney injury; BMI, body mass index; CKD, chronic kidney disease; DEI, dietary energy intake; DPI, dietary protein intake; GFR, glomerular filtration rate; nPCR, normalized protein catabolic rate; nPNA, normalized protein nitrogen appearance; PEW, protein-energy wasting.

Reprinted from Fouque D, Kalantar-Zadeh K, Kopple J et al. A proposed nomenclature and diagnostic criteria for protein-energy wasting in acute and chronic kidney disease. Kidney Int 2008;73:391-398.

Undoubtedly, these proposed criteria have a great applicability in clinical practice not only because the measurements and methods are readily available in the majority of the centers but also because it provides clearly indications on how to use them to reach a diagnosis. However, the validity of this proposal has to
be tested. In addition, despite the recognized association of most of these parameters with poor outcomes in the population of patients with CKD, it is important to be aware of their limitations as markers of PEW to properly interpret the results. Table 18-2 lists the main limitations of the commonly used parameters.

Table 18-2. Main limitations of commonly used parameters for nutritional assessment in chronic kidney disease

Parameter	Limitations
Serum albumin	Large pool size and long half-life. Decreases with fluid overload and inflammation.
Serum prealbumin	Decreases with inflammation and is elevated because of decreased renal catabolism.
Serum cholesterol	Poor sensibility and specificity to nutritional condition.
BMI	Influenced by lean mass and hydration status. Cutoff point may differ according to ethnicity and age.
Body fat	High inter- and intraobserver variability when estimated by skinfold thickness.
Midarm muscle circumference/area	Indirect estimation of muscle mass, high inter and intraobserver variability.
Creatinine appearance	Depends on the precision of collected urine and dialysate. Is affected by meat ingestion.
Dietary intake
Food records	Underreporting of energy intake.
nPNA	Great day-to-day variation in energy intake. In catabolic condition nPNA may exceed protein intake. A single measurement may not reflect the usual protein intake. Errors in urine collection can lead to misleading results.
nPNA, normalized protein nitrogen appearance.

Additionally, the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF-K/DOQI) Clinical Practice Guidelines for Nutrition in CKD as well as the European Best Practice Guideline on Nutrition have recommended the use of 7-point Subjective Global Assessment because low SGA values are associated with high rates of morbidity and mortality in patients undergoing maintenance dialysis. Many other potential indicators of PEW such as appetite assessment questionnaires, composite nutrition score systems, handgrip strength, and inflammatory
markers have been proposed and could also be included in the panel of nutritional assessment parameters.

Monitoring the nutritional status on a regular basis is the key to early detect nutritional disturbances, to evaluate the response of nutritional interventions, and to motivate and improve patient’s compliance to the dietary therapy. There is no definitive protocol for routine follow-up, but in general body weight, body mass index (BMI) and normalized protein equivalent of nitrogen appearance (nPNA) should be measured monthly for patients undergoing dialysis therapy and every 1 to 3 months for CKD stages 4 and 5. Serum albumin, prealbumin, and cholesterol should be determined every 3 months in clinically stable patients. Other anthropometric measurements, dietary interviews, and SGA should be obtained every 6 months or more often in those patients at risk of developing PEW or with established PEW.

Diet Therapy for Adult Patients with Chronic Kidney Disease

For assessing and prescribing energy and most nutrient intake for patients with CKD, actual edema-free body weight (BWef) should be used if BW is between 95% and 115% of the median standard body weight (SBW). Adjusted edema-free body weight (aBW_ef) should be calculated when patient’s weight is lower than 95% or higher than 115% according to the following equation:

aBW_ef = BW_ef + [(SBW − BW_ef) × 0.25]

Energy

Chronic Kidney Disease Stages 2 to 5 Not on Maintenance Dialysis

There is compelling evidence suggesting that the energy expenditure of clinically stable patients with CKD not on dialysis treatment is similar or even lower than that of healthy subjects. For this reason, the energy recommendation ranges between 30 and 35 kcal/kg/day, which are values close to those recommended for healthy individuals. Ideally, for estimating the energy requirement of a patient with CKD, factors such as age, gender, physical activity level, nutritional status, and the presence of metabolic disturbances and comorbidities should be considered. However, the contribution of these factors for the daily energy expenditure for this particular group of patients is unknown. Therefore, predictive equations and physical activity factors developed for other populations have been used as an alternative for patients with CKD. Harris and Benedict’s equation and Schofield’s equation are among the most used in clinical practice to estimate resting energy expenditure or basal metabolic rate. However, there are concerns regarding the validity of these equations for patients with CKD. Physical activity is another important component for the estimation of energy requirement. Although some studies indicate that most patients with CKD have low physical activity level (PAL), it is not known whether the PAL factor of these patients is similar to the ones proposed for healthy subjects. For these reasons, estimation of energy requirement by using either the energy recommended by guidelines or estimated by equations can be very helpful only as an initial guide for planning the diet.
The best way to evaluate whether the estimated energy requirement is adequate in a patient with CKD is by monitoring the patient’s nutritional status and making appropriate adjustments as needed.

Most patients with CKD stage 2-5 who are not on maintenance dialysis are potentially on a low-protein diet, and thus it is important to provide an amount of energy sufficient to guarantee at least a neutral nitrogen balance. Therefore, diets containing less than 25 kcal/kg/day should be avoided even for patients who need to lose weight.

Chronic Kidney Disease Stage 5 on Maintenance Dialysis

It is well demonstrated that hemodialysis is a catabolic event leading to increased energy and protein catabolism, not only during the dialysis session but also over 2 hours following the completion of hemodialysis. However, several lines of evidence indicate that this effect can be reverted by intradialytic nutritional supplementation. Therefore, it seems advisable to provide, whenever possible, oral supplements or even a well-designed meal/snack for patients during hemodialysis. To avoid vomiting, it is recommended to provide the supplement/food during the initial hours of the dialysis session or potentially within 1 hour prior to initiating hemodialysis.

Metabolic derangements such as hyperparathyroidism and acidosis as well as inflammation may become more severe in patients with CKD undergoing maintenance dialysis and can result in increased energy expenditure. However, except if persistent and severe, the impact of these abnormalities on the energy requirement may be small. Indeed, the daily energy expenditure of patients on dialysis seems to be comparable to that of subjects with normal renal function as demonstrated by several studies. The NKF-K/DOQI Clinical Practice Guidelines for Nutrition in Chronic Renal Failure recommends a daily energy intake of 35 kcal/kg/day for patients who are less than 60 years of age and 30-35 kcal/kg/day for those older than 60 years. The recent published European Best Practice Guideline on Nutrition recommends 30-40 kcal/kg/day adjusted for age, gender, and to the best estimation of physical activity level.

For patients receiving peritoneal dialysis therapy, the energy provided by the absorbed glucose has to be considered in the estimation of energy requirement, particularly in those patients with overweight or obesity. Although the extra source of energy could be helpful for planning a high-energy diet for patients with PEW, the constant glucose absorption may have a negative effect on appetite.

Episodes of low energy intake because of decreased appetite are not uncommon in patients undergoing dialysis treatment. This condition is often challenging for the dialysis care team, and efforts should be made to identify the underlying causes of anorexia while intensive dietary counseling should be provided. The first step is to analyze the actual food intake through a 24-hour recall or 3-day food record to identify potential modifications on amounts or food choices to improve energy intake. Prescribing a less restrictive diet and taking into considerations the patient’s food preferences can also be helpful to improve overall intake.
Additionally, lists containing high-energy density conventional foods and recipes should be provided. If no satisfactory response is achieved within a short period, renal-specific oral supplements or even tube feeding should be considered.

Protein

Chronic Kidney Disease Stages 2 to 5 Not on Maintenance Dialysis

Despite the controversies regarding the role of protein restriction in slowing progression of CKD, the benefits of such dietary manipulation in preventing or ameliorating the accumulation of nitrogen waste products, metabolic and hormonal disorders (acidosis, glucose intolerance, and hyperparathyroidism), and proteinuria are unquestionable. In addition, there is evidence that well-designed diets, planned by skilled dietitians, and followed by motivated and compliant patients are effective and do not have harmful effects on the nutritional condition.

In general, it is recommended a protein intake ranging from 0.6 g/kg/day to a maximum of 0.8 g/kg/day providing at least 50% to 60% of high-biologic-value proteins to ensure a sufficient amount of essential amino acids. For patients with CKD and diabetes, a diet with 0.8 g/kg/day has been recommended. Because typical Western diets contain larger amounts of proteins, usually between 1.0 and 1.5 g/kg/day, the initial adherence to low-protein diets is somewhat difficult. For this reason, the dietary plan should be individualized taking into account the patient food habits and preferences. Food choices lists according to the protein content are important tools to allow greater variability in the diet along with enhanced palatability. Moreover, it has been shown that compliance increases when interventions involve patient self-management, with ongoing feedback, regular monitoring, and support.

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