Faculty Bibliography

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.

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.

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.

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.

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.

Dietary phosphorus restriction is recommended to help control hyperphosphatemia in hemodialysis patients, but many high-phosphorus foods are important sources of protein. In this review, we examine whether restricting dietary phosphorus compromises protein status in hemodialysis patients. Although dietary phosphorus and protein are highly correlated, phosphorus intakes can range up to 600 mg/day for a given energy and protein intake level. Furthermore, the collinearity of phosphorus and protein may be biased because the phosphorus burden of food depends on: (1) the presence of phosphate additives, (2) food preparation method, and (3) bioavailability of phosphorus, which are often unaccounted for in nutrition assessments. Ultimately, we argue that clinically relevant reductions in phosphorus intake can be made without limiting protein intake by avoiding phosphate additives in processed foods, using wet cooking methods such as boiling, and if needed, substituting high-phosphorus foods for nutritionally equivalent foods that are lower in bioavailable phosphorus.

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(R) 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.

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.

BACKGROUND:Recent studies have demonstrated considerable interindividual variability in postprandial glucose response (PPGR) to the same foods, suggesting the need for more precise methods for predicting and controlling PPGR. In the Personal Nutrition Project, the investigators tested a precision nutrition algorithm for predicting an individual's PPGR. OBJECTIVE:This study aimed to compare changes in glycemic variability (GV) and HbA1c in 2 calorie-restricted weight loss diets in adults with prediabetes or moderately controlled type 2 diabetes (T2D), which were tertiary outcomes of the Personal Diet Study. METHODS:The Personal Diet Study was a randomized clinical trial to compare a 1-size-fits-all low-fat diet (hereafter, standardized) with a personalized diet (hereafter, personalized). Both groups received behavioral weight loss counseling and were instructed to self-monitor diets using a smartphone application. The personalized arm received personalized feedback through the application to reduce their PPGR. Continuous glucose monitoring (CGM) data were collected at baseline, 3 mo and 6 mo. Changes in mean amplitude of glycemic excursions (MAGEs) and HbA1c at 6 mo were assessed. We performed an intention-to-treat analysis using linear mixed regressions. RESULTS:We included 156 participants [66.5% women, 55.7% White, 24.1% Black, mean age 59.1 y (standard deviation (SD) = 10.7 y)] in these analyses (standardized = 75, personalized = 81). MAGE decreased by 0.83 mg/dL per month for standardized (95% CI: 0.21, 1.46 mg/dL; P = 0.009) and 0.79 mg/dL per month for personalized (95% CI: 0.19, 1.39 mg/dL; P = 0.010) diet, with no between-group differences (P = 0.92). Trends were similar for HbA1c values. CONCLUSIONS:Personalized diet did not result in an increased reduction in GV or HbA1c in patients with prediabetes and moderately controlled T2D, compared with a standardized diet. Additional subgroup analyses may help to identify patients who are more likely to benefit from this personalized intervention. This trial was registered at clinicaltrials.gov as NCT03336411.

OBJECTIVES/OBJECTIVE: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/METHODS:, 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.