Current Controversies in Kidney Nutrition.

Dietetic practice aims to help people modify their diet to slow disease progression and manage disease-related complications while also meeting their nutritional and personal dietary needs. This can be challenging in people with kidney failure undergoing dialysis, particularly in our current food environment and culture. Fortunately, advancements in nutritional-behavioral science and technology are providing new avenues and resources to help meet the challenge. However, progress is slow, and much of dietetic practice in the dialysis population still relies on the interpretation, translation, and application of low-quality, indirect evidence. This Special Issue of Seminars in Dialysis provides readers with an update on and critical insights into some of the major issues and controversies impacting the field of kidney nutrition today.

Seeing the Whole Picture: Evaluating the Contribution of Whole Grains to Phosphorus Exposure in People With Kidney Failure Undergoing Dialysis Treatment.

Excessive dietary phosphorus is a concern among patients with kidney failure undergoing dialysis treatment because it may contribute to hyperparathyroidism and hyperphosphatemia. A long-standing but untested component of the low-phosphorus diet is the promotion of refined grains over whole grains. This paper reviews the scientific premise for restricting whole grains in the dialysis population and estimates phosphorus exposure from grain products based on three grain intake patterns modeled from reported intakes in the general US population, adjusting for the presence of phosphorus additives and phosphorus bioavailability: (1) standard grain intake, (2) 100% refined grain intake, and (3) mixed (50/50 whole and refined grain) intake. Although estimated phosphorus exposure from grains was higher with the mixed grain pattern (231 mg/day) compared to the 100% refined grain pattern (127 mg/day), the amount of additional phosphorus from grains was relatively low. Given the lack of strong evidence for restricting whole grains in people with CKD, as well as the potential health benefits of whole grains, clinical trials are warranted to address the efficacy and health impact of this practice.

A Systematic Review of Online Resources for the Dietary Management of Hyperphosphatemia in People With Chronic Kidney Disease.

OBJECTIVE: Internet search engines and social media websites are prominent and growing sources of dietary information for people with chronic kidney disease (CKD) and their healthcare providers. However, nutrition therapy for CKD is undergoing a paradigm shift, which may lead to inconsistent advice for managing hyperphosphatemia. The aim of this study was to summarize and evaluate online resources for phosphorus-specific nutrition therapy. DESIGN AND METHODS: Patient-facing resources were collected from Google, Yahoo, and Facebook in June-July 2021. Using nine independent search terms, the first 100 hits were reviewed. Dietary advice for food types, food groups, food subgroups, and individual food items was categorized as "restricted," "recommended," "mixed," and "not mentioned." Information on publication date, source, and author(s), phosphorus bioavailability, and demineralization were also collected. RESULTS: After removing duplicates, 199 resources from Google and Yahoo and 33 from Facebook were reviewed. Resources ranged from 2005 to 2021 and were primarily authored by registered dietitians and medical doctors (65% and 31%, respectively). Dietary advice mostly focuses on restricting high-phosphorus foods and phosphorus additive-based processed foods. Dietary restrictions were generally consistent with the traditional low-phosphorus diet, which targets whole grains, dairy, and plant-based protein foods, although major inconsistencies were noted. Phosphorus bioavailability and demineralization were rarely mentioned (16% and 8%, respectively). Similar findings were found on Facebook, but the limited number of resources limited meaningful comparisons. CONCLUSION: Results showed that online resources for phosphorus-specific nutrition therapy are highly restrictive of heart-healthy food items and contain significant inconsistencies. Given the widespread and increasing use of online resources by people with CKD and health care professionals to inform dietary choices, efforts are urgently needed to establish consensus for phosphorus-specific nutrition therapy. Until then, the findings of this study provide a basis for increasing awareness of the potential for confusion arising from online resources.

Deconstructing Disease-Related Malnutrition: A New Assessment Framework for Clinical Practice.

Protein-energy wasting (PEW) is a key cause of functional impairment and poor health outcomes in people with chronic kidney disease. While PEW can be mitigated with nutrition therapy, it is a complex myriad of disorders with numerous interacting etiologies and corresponding presentations, which make it difficult to diagnose and manage in practice. A variety of scoring rubrics have been developed to facilitate malnutrition assessment. Although these tools have greatly benefited the recognition and treatment of PEW, the typical format of grading specified PEW indicators has the potential to overlook or overstate highly relevant individual-specific factors. This review presents a simple framework for malnutrition assessment that can be used to complement and evaluate conventional assessment tools. Unlike standard tools, which are designed to identify and rate malnutrition risk and severity, the malnutrition framework is conceptual model that organizes PEW assessment into three distinct, but interacting facets of PEW risk: nutrient balance, nutrition status, and malnutrition risk. The new framework encourages critical thinking about PEW risk that may help clinicians plan and interpret assessments to efficiently and effectively manage this condition.

'Phos'tering a Clear Message: The Evolution of Dietary Phosphorus Management in Chronic Kidney Disease.

Phosphorus is a vital nutrient, but disturbances in phosphorus homeostasis are central to chronic kidney disease-mineral and bone disorder. To minimize disturbances, traditional dietary guidance focused on a numerical phosphorus target leading to the exclusion of many healthy foods and implementation challenges. Contemporary phosphorus guidance focuses on dietary source, avoiding additives, and emphasizing low-phosphorus bioaccessibility foods, leading to a more liberal approach. Additional work is needed to demonstrate the efficacy of these contemporary approaches and understand the influence of specific foods, processing, and cooking methods. Unfortunately, patient education using traditional and contemporary strategies may give mixed messages, particularly related to plant-based foods. Thus, greater clarity on the effects of specific foods and dietary patterns may improve phosphorus education. This review aims to discuss the evolution of dietary phosphorus management while highlighting areas for future research that can help move the field toward stronger evidence-based guidance to prevent and treat hyperphosphatemia.

An Evaluation of Alternative Technology-Supported Counseling Approaches to Promote Multiple Lifestyle Behavior Changes in Patients With Type 2 Diabetes and Chronic Kidney Disease.

OBJECTIVES: Although technology-supported interventions are effective for reducing chronic disease risk, little is known about the relative and combined efficacy of mobile health strategies aimed at multiple lifestyle factors. The purpose of this clinical trial is to evaluate the efficacy of technology-supported behavioral intervention strategies for managing multiple lifestyle-related health outcomes in overweight adults with type 2 diabetes (T2D) and chronic kidney disease (CKD). DESIGN AND METHODS: Using a 2 × 2 factorial design, adults with excess body weight (body mass index ≥27 kg/m2, age ≥40 years), T2D, and CKD stages 2-4 were randomized to an advice control group, or remotely delivered programs consisting of synchronous group-based education (all groups), plus (1) Social Cognitive Theory-based behavioral counseling and/or (2) mobile self-monitoring of diet and physical activity. All programs targeted weight loss, greater physical activity, and lower intakes of sodium and phosphorus-containing food additives. RESULTS: Of 256 randomized participants, 186 (73%) completed 6-month assessments. Compared to the ADVICE group, mHealth interventions did not result in significant changes in weight loss, or urinary sodium and phosphorus excretion. In aggregate analyses, groups receiving mobile self-monitoring had greater weight loss at 3 months (P = .02), but between 3 and 6 months, weight losses plateaued, and by 6 months, the differences were no longer statistically significant. CONCLUSIONS: When engaging patients with T2D and CKD in multiple behavior changes, self-monitoring diet and physical activity demonstrated significantly larger short-term weight losses. Theory-based behavioral counseling alone was no better than baseline advice and demonstrated no interaction effect with self-monitoring.

A Novel Approach for Managing Protein-Energy Wasting in People With Kidney Failure Undergoing Maintenance Hemodialysis: Rationale and Call for Trials.

Protein-energy wasting (PEW) is a unique presentation of protein-energy malnutrition in people with kidney disease that is characterized by body protein catabolism exceeding anabolism. PEW is especially common in patients undergoing maintenance hemodialysis (HD) treatment. Dietary guidelines for managing PEW in HD patients primarily focus on protein adequacy and typically promote the intake of animal-based protein foods. Although intake of protein and essential amino acids is important for protein synthesis, the emphasis on protein adequacy largely fails to address-and may actually exacerbate-many of the root causes of PEW. This perspective examines the dietary determinants of PEW in people undergoing HD treatment, with an emphasis on upstream disease-related factors that reduce dietary protein utilization and impair dietary intakes. From this, we present a theoretical diet model for managing PEW that includes etiology-based dietary strategies to address barriers to intake and treat disease-related factors, as well as supportive dietary strategies to promote adequate energy and protein intakes. Given the complexity of diet-disease interactions in the pathogenesis of PEW, and its ongoing burden in HD patients, interventional trials are urgently needed to evaluate alternative diet therapy approaches for PEW in this population.

Feasibility and Acceptability of mHealth Interventions for Managing Hyperphosphatemia in Patients Undergoing Hemodialysis.

OBJECTIVE: The objective of the study was to evaluate the feasibility and acceptability of mobile health (mHealth) phosphorus management programs in hemodialysis (HD) patients. METHODS: Patients receiving thrice-weekly HD who had 3-month average serum phosphorus of >5.5 mg/dL were randomized to one of the three self-directed phosphorus management programs delivered using tablet PCs: (1) educational videos and handouts (Education), (2) education intervention plus mobile self-monitoring with email feedback (Monitoring), or (3) education and monitoring interventions plus social cognitive theory-based behavioral videos (Combined). Feasibility and acceptability were assessed based on enrollment and retention and training needs (feasibility) and adherence to self-monitoring and reported satisfaction (acceptability). RESULTS: Of 312 patients, 56 expressed interest, and 40 were enrolled. The majority of participants (80%) completed the 6-month study; none withdrew for intervention-related reasons. The Monitoring and Combined groups received 44 ± 15 minutes of technology training, which was considered adequate by most (75%). Self-monitoring rates were initially high, with 78% and 71% of the participants recording at least one meal and phosphate binder in week 1, respectively, but decreased over time to 15% and 9% in the final week. Most participants reported that self-monitoring helped them stay motivated (64%), track nutrients (80%), and understand how to change diet (76%), and nearly two-thirds of participants (64%) stated that they would like to continue using the tablet PC to manage their health. However, few participants (16%) indicated that self-monitoring was worth the effort. The Monitoring and Combined groups did not differ from the Education group in study outcomes. CONCLUSION: Although the mHealth programs were generally well received, self-monitoring rates decreased substantially over time and were unaffected by social cognitive theory-based videos. Self-directed mHealth programs may be a useful adjunct to standard care but should be compared to more resource intensive programs (e.g., involving more "live" contact with a dietitian) to determine overall cost-effectiveness and role in HD care.

Managing Hyperkalemia: Another Benefit of Exercise in People With Chronic Kidney Disease?

People with chronic kidney disease (CKD) are at increased risk of hyperkalemia, an electrolyte abnormality that can cause serious, sometimes fatal, cardiac arrhythmias. Muscle contraction causes potassium to be released from cells, increasing serum potassium concentrations. However, these effects are transient, and the long-term impact of exercise training on hyperkalemia risk in CKD patients is largely unknown. In this review, we examine the effects of exercise on factors affecting potassium balance in people with CKD, highlighting the potential benefits of regular exercise on hyperkalemia risk in this population. Although regular exercise is already recommended for people with CKD, research examining this hypothesis may lead to novel therapeutic treatments for this life-threatening condition.

Managing protein-energy wasting in hemodialysis patients: A comparison of animal- and plant-based protein foods.

Protein-energy wasting (PEW) is a major diet-related complication in hemodialysis (HD) patients. Nutrient-based dietary guidelines emphasize animal-based protein foods for preventing and managing PEW in HD patients. Although dietary protein intake is important for protein anabolism, other dietary factors contribute to PEW. In this article, we examine the diet-related etiologies of PEW in HD patients, and discuss how they may be affected differently by animal- and plant-based protein foods. In general, animal foods are superior sources of protein, but may contribute more to metabolic derangements that cause PEW. Given the potential mixed effects of animal-based protein foods on PEW, human research studies are needed to determine the impact of liberalizing the diet to allow plant-based protein foods on protein status.

Determinants and the Role of Self-Efficacy in a Sodium-Reduction Trial in Hemodialysis Patients.

OBJECTIVE: This study was to assess the impact of baseline dietary self-efficacy on the effect of a dietary intervention to reduce sodium intake in patients undergoing hemodialysis (HD) and to identify determinants of low dietary self-efficacy. METHODS: This is a post hoc analysis of the BalanceWise study, a randomized controlled trial that aimed to reduce dietary sodium intake in HD patients recruited from 17 dialysis centers in Pennsylvania. The main outcome measures include dietary self-efficacy and reported dietary sodium density. Analysis of variance with post hoc group-wise comparison was used to examine the effect of baseline dietary self-efficacy on changes in reported sodium density in the intervention and control groups at 8 and 16 weeks. Chi-square test, independent t tests, or Wilcoxon rank-sum tests were used to identify determinants of low dietary self-efficacy. RESULTS: The interaction between dietary self-efficacy and the impact of the intervention on changes in reported dietary sodium density approached significance at 8 and 16 weeks (P interaction = 0.051 and 0.06, respectively). Younger age and perceived income inadequacy were significantly associated with low self-efficacy in patients undergoing HD. CONCLUSION: The benefits of dietary interventions designed to improve self-efficacy may differ by the baseline self-efficacy status. This may be particularly important for HD patients who are younger and report inadequate income as they had lower dietary self-efficacy.

Assessment and misassessment of potassium, phosphorus, and protein in the hemodialysis diet.

Diet is a key determinant of several common and serious disease complications in hemodialysis (HD) patients. The recommended balance and variety of foods in the HD diet is designed to limit high potassium and phosphorus foods while maintaining protein adequacy. In this report, we examine the potassium, phosphorus, and protein content of foods, and identify critical challenges, and potential pitfalls when translating nutrient prescriptions into dietary guidelines. Our findings highlight the importance of individualized counseling based on a comprehensive dietary assessment by trained diet professionals, namely renal dietitians, for managing diet-related complications in HD patients.

Fetuin-A and Risk of Diabetes Independent of Liver Fat Content: The Multi-Ethnic Study of Atherosclerosis.

Fetuin-A is a hepatic secretory protein and a novel risk factor for diabetes. However, it remains unclear whether the association between high levels of fetuin-A and diabetes can be attributed to nonalcoholic fatty liver disease. We conducted a case-cohort study among 1,957 subcohort members and 455 incident diabetes cases in the Multi-Ethnic Study of Atherosclerosis, a multicenter US study of Caucasian, African-American, Hispanic, and Chinese-American adults aged 45-84 years. Serum fetuin-A and computed tomography-determined liver fat content were measured from samples collected at baseline (2000-2002). In multivariable Cox proportional hazards models with follow-up through 2012, a higher fetuin-A level was associated with a higher risk of diabetes, with a stronger association among women (for top quartile vs. bottom, hazard ratio (HR) = 3.36, 95% confidence interval (CI): 2.08, 5.44) than among men (HR = 1.47, 95% CI: 0.93, 2.35) (P-heterogeneity = 0.001). Adjustment for liver fat content attenuated these associations slightly (women: HR = 2.61, 95% CI: 1.59, 4.26; men: HR = 1.32, 95% CI: 0.84, 2.08). In this study, we observed a particularly strong association of fetuin-A with diabetes risk in women that could not be explained by liver fat.

Effect of high-protein meals during hemodialysis combined with lanthanum carbonate in hypoalbuminemic dialysis patients: findings from the FrEDI randomized controlled trial.

BACKGROUND: Inadequate protein intake and hypoalbuminemia, indicators of protein-energy wasting, are among the strongest mortality predictors in hemodialysis patients. Hemodialysis patients are frequently counseled on dietary phosphorus restriction, which may inadvertently lead to decreased protein intake. We hypothesized that, in hypoalbuminemic hemodialysis patients, provision of high-protein meals during hemodialysis combined with a potent phosphorus binder increases serum albumin without raising phosphorus levels. METHODS: We conducted a randomized controlled trial in 110 adults undergoing thrice-weekly hemodialysis with serum albumin <4.0 g/dL recruited between July 2010 and October 2011 from eight Southern California dialysis units. Patients were randomly assigned to receive high-protein (50-55 g) meals during dialysis, providing 400-500 mg phosphorus, combined with lanthanum carbonate versus low-protein (<1 g) meals during dialysis, providing <20 mg phosphorus. Prescribed nonlanthanum phosphorus binders were continued over an 8-week period. The primary composite outcome was a rise in serum albumin of ≥0.2 g/dL while maintaining phosphorus between 3.5-<5.5 mg/dL. Secondary outcomes included achievement of the primary outcome's individual endpoints and changes in mineral and bone disease and inflammatory markers. RESULTS: Among 106 participants who satisfied the trial entrance criteria, 27% ( n = 15) and 12% ( n = 6) of patients in the high-protein versus low-protein hemodialysis meal groups, respectively, achieved the primary outcome (intention-to-treat P-value = 0.045). A lower proportion of patients in the high-protein versus low-protein intake groups experienced a meaningful rise in interleukin-6 levels: 9% versus 31%, respectively (P = 0.009). No serious adverse events were observed. CONCLUSION: In hypoalbuminemic hemodialysis patients, high-protein meals during dialysis combined with lanthanum carbonate are safe and increase serum albumin while controlling phosphorus.

Examining the Proportion of Dietary Phosphorus From Plants, Animals, and Food Additives Excreted in Urine.

Phosphorus bioavailability is an emerging topic of interest in the field of renal nutrition that has important research and clinical implications. Estimates of phosphorus bioavailability, based on digestibility, indicate that bioavailability of phosphorus increases from plants to animals to food additives. In this commentary, we examined the proportion of dietary phosphorus from plants, animals, and food additives excreted in urine from four controlled-feeding studies conducted in healthy adults and patients with chronic kidney disease. As expected, a smaller proportion of phosphorus from plant foods was excreted in urine compared to animal foods. However, contrary to expectations, phosphorus from food additives appeared to be incompletely absorbed. The apparent discrepancy between digestibility of phosphorus additives and the proportion excreted in urine suggests a need for human balance studies to determine the bioavailability of different sources of phosphorus.

Phosphate Additive Avoidance in Chronic Kidney Disease.

IN BRIEF Dietary guidelines for patients with diabetes extend beyond glycemic management to include recommendations for mitigating chronic disease risk. This review summarizes the literature suggesting that excess dietary phosphorus intake may increase the risk of skeletal and cardiovascular disease in patients who are in the early stages of chronic kidney disease (CKD) despite having normal serum phosphorus concentrations. It explores strategies for limiting dietary phosphorus, emphasizing that food additives, as a major source of highly bioavailable dietary phosphorus, may be a suitable target. Although the evidence for restricting phosphorus-based food additives in early CKD is limited, diabetes clinicians should monitor ongoing research aimed at assessing its efficacy.

North American experience with Low protein diet for Non-dialysis-dependent chronic kidney disease.

Whereas in many parts of the world a low protein diet (LPD, 0.6-0.8 g/kg/day) is routinely prescribed for the management of patients with non-dialysis-dependent chronic kidney disease (CKD), this practice is infrequent in North America. The historical underpinnings related to LPD in the USA including the non-conclusive results of the Modification of Diet in Renal Disease Study may have played a role. Overall trends to initiate dialysis earlier in the course of CKD in the US allowed less time for LPD prescription. The usual dietary intake in the US includes high dietary protein content, which is in sharp contradistinction to that of a LPD. The fear of engendering or worsening protein-energy wasting may be an important handicap as suggested by a pilot survey of US nephrologists; nevertheless, there is also potential interest and enthusiasm in gaining further insight regarding LPD's utility in both research and in practice. Racial/ethnic disparities in the US and patients' adherence are additional challenges. Adherence should be monitored by well-trained dietitians by means of both dietary assessment techniques and 24-h urine collections to estimate dietary protein intake using urinary urea nitrogen (UUN). While keto-analogues are not currently available in the USA, there are other oral nutritional supplements for the provision of high-biologic-value proteins along with dietary energy intake of 30-35 Cal/kg/day available. Different treatment strategies related to dietary intake may help circumvent the protein- energy wasting apprehension and offer novel conservative approaches for CKD management in North America.

Nutrient Non-equivalence: Does Restricting High-Potassium Plant Foods Help to Prevent Hyperkalemia in Hemodialysis Patients?

Hemodialysis patients are often advised to limit their intake of high-potassium foods to help manage hyperkalemia. However, the benefits of this practice are entirely theoretical and not supported by rigorous randomized controlled trials. The hypothesis that potassium restriction is useful is based on the assumption that different sources of dietary potassium are therapeutically equivalent. In fact, animal and plant sources of potassium may differ in their potential to contribute to hyperkalemia. In this commentary, we summarize the historical research basis for limiting high-potassium foods. Ultimately, we conclude that this approach is not evidence-based and may actually present harm to patients. However, given the uncertainty arising from the paucity of conclusive data, we agree that until the appropriate intervention studies are conducted, practitioners should continue to advise restriction of high-potassium foods.

Exploring Problems in Following the Hemodialysis Diet and Their Relation to Energy and Nutrient Intakes: The BalanceWise Study.

OBJECTIVE: To identify the problems experienced by hemodialysis (HD) patients in attempting to follow the HD diet and their relation to energy and nutrient intakes. DESIGN: Cross-sectional analysis of baseline data from the BalanceWise Study. SUBJECTS: Participants included community-dwelling adults recruited from outpatient HD centers. After excluding participants with incomplete dietary analyses (n = 50), 140 African American and white (40/60%) men and women (52/48%) on chronic intermittent HD for at least 3 months (median 3 years) were included. INTERVENTION: Participant responses, on a 5-point Likert scale ranging from "not at all a problem" to "a very important problem for me," to 34 questions pertaining to potential barriers to following the HD diet in the previous 2 months were classified as either a problem (1) or not a problem (2-5). MAIN OUTCOME MEASURE: Energy and nutrient intakes determined using the Nutrition Data System for Research® based on 3, non-consecutive, unscheduled, 2-pass 24-hour dietary recalls collected on 1 dialysis and 1 non-dialysis weekday, and 1 non-dialysis weekend day. RESULTS: More than half of participants reported having problems related to specific behavioral factors (e.g., feeling deprived), technical difficulties (e.g., tracking nutrients), and physical condition (e.g., appetite), but issues of time and food preparation and behavioral factors tended to be most deterministic of reported dietary intakes. Longer duration of HD was associated with lower intakes of protein, potassium, and phosphorus (P < .05). CONCLUSION: Registered dietitian nutritionists should consider issues of time and food preparation, and behavioral factors in their nutrition assessment of HD patients and should continually monitor HD patients for changes in protein intake that may occur over time.