Severe dietary protein restriction in overt diabetic nephropathy: benefits or risks?

Dietary recommendations for people with diabetes in special situations: a position statement report by Arabic Association for the Study of Diabetes and metabolism (AASD)

BACKGROUND

Diabetes is a significant global health concern. Regional factors play a crucial role in determining the appropriate diet for patients.

MAIN BODY

The Arabic Association for the Study of Diabetes and Metabolism has developed a position statement that addresses the dietary needs of patients in the context of low income and cultural dietary habits. This statement aims to explore the most suitable diet for Middle East and North Africa (MENA) region and provide guidance for physicians to overcome barriers in optimal care. While most dietary guidelines focus on uncomplicated diabetes, it's essential to recognize that diabetes often coexists with other common diseases in our region.

CONCLUSION

International guidelines cannot be directly applied to the Egypt and Arab countries due to cultural and dietary differences. Our position statement shares valuable insights into managing diabetes in special situations and diverse clinical settings within this region. These recommendations are flexible, considering personal, cultural, and traditional differences.

Association between dietary protein intake and mortality among patients with diabetic kidney disease

AIMS

This study aimed to investigate the association between dietary protein intake and mortality among patients with diabetic kidney disease.

METHODS

The research encompassed a total of 2901 participants diagnosed with diabetic kidney disease, drawn from the National Health and Nutrition Examination Survey (NHANES). To determine outcomes related to all-cause and cardiovascular mortality, connections were established with the National Death Index up until December 31, 2019. Estimations of hazard ratios (HRs) and their corresponding 95 % confidence intervals (CIs) were conducted using Cox proportional hazard ratio models.

RESULTS

During the 261,239 person-years of follow-up, 1236 deaths were recorded. After multivariate adjustment, the weighted hazard ratio (HR) and 95 % CIs for participants with 1.0-1.2 g/kg of protein intake was 0.65 (0.44, 0.96) for all-cause mortality. A higher proportion of animal protein intake was found to be associated with an increased mortality risk. Stratified analyses showed that higher protein intake benefited older participants.

CONCLUSIONS

In diabetic kidney disease patients, 1.0-1.2 g/kg of protein was associated with lower mortality and 0.6-1.2 g/kg of protein especially benefitted patients ≥60 years.

Intermittent protein restriction before but not after the onset of diabetic kidney disease attenuates disease progression in mice

Background

High dietary protein intake exacerbates proteinuria in individuals with diabetic kidney disease (DKD). However, studies on the impacts of low protein diet (LPD) on DKD have yielded conflicting results. Furthermore, patient compliance to continuous protein restriction is challenging.

Objective

The current study aims to investigate the effects of intermittent protein restriction (IPR) on disease progression of DKD.

Methods

Diabetic KK-Ay mice were used in this study. For the IPR treatment, three consecutive days of LPD were followed by four consecutive days of normal protein diet (NPD) within each week. For early intervention, mice received IPR before DKD onset. For late intervention, mice received IPR after DKD onset. In both experiments, age-matched mice fed continuous NPD served as the control group. Kidney morphology, structure and function of mice in different groups were examined.

Results

Intermittent protein restriction before DKD onset ameliorated pathological changes in kidney, including nephromegaly, glomerular hyperfiltration, tubular injuries and proteinuria, without improving glycemic control. Meanwhile, IPR initiated after DKD onset showed no renoprotective effects despite improved glucose homeostasis.

Conclusion

Intermittent protein restriction before rather than after DKD onset protects kidneys, and the impacts of IPR on the kidneys are independent of glycemic control. IPR shows promise as an effective strategy for managing DKD and improving patient compliance.

Secular Trend in GFR Decline in Non-Dialysis CKD Based on Observational Data From Standard of Care Arms of Trials

RATIONALE & OBJECTIVE

The standard of care (SoC) group of randomized controlled trials (RCTs) is a useful setting to explore the secular trends in kidney disease progression because implementation of best clinical practices is pursued for all patients enrolled in trials. This meta-analysis evaluated the secular trend in the change of glomerular filtration rate (GFR) decline in the SoC arm of RCTs in chronic kidney disease (CKD) published in the last 30 years.

STUDY DESIGN

Systematic review and meta-analysis of the SoC arms of RCTs analyzed as an observational study.

SETTING & STUDY POPULATIONS

Adult patients with CKD enrolled in the SoC arm of RCTs.

SELECTION CRITERIA FOR STUDIES

Phase 3 RCTs evaluating GFR decline as an outcome in SoC arms.

DATA EXTRACTION

Two independent reviewers evaluated RCTs for eligibility and extracted relevant data.

ANALYTICAL APPROACH

The mean of GFR declines extracted in the SoC arm of selected RCTs were pooled by using a random effects model. Meta-regression analyses were performed to identify factors that may explain heterogeneity.

RESULTS

The SoC arms from 92 RCTs were included in the meta-analysis with a total of 32,202 patients. The overall mean GFR decline was-4.00 (95% CI, -4.55 to-3.44) mL/min/1.73m2 per year in the SoC arms with a high level of heterogeneity (I2, 98.4% [95% CI, 98.2-98.5], P<0.001). Meta-regression analysis showed an association between publication year (β estimate, 0.09 [95% CI, 0.032-0.148], P=0.003) and reduction in GFR over time. When evaluating publication decade categorically, GFR decline was-5.44 (95% CI, -7.15 to-3.73), -3.92 (95% CI, -4.82 to-3.02), and -3.20 (95% CI, -3.75 to -2.64) mL/min/1.73m2 per year during 1991-2000, 2001-2010, and 2011-2023, respectively. Using meta-regression, the heterogeneity of GFR decline was mainly explained by age and proteinuria.

LIMITATIONS

Different methods assessing GFR in selected trials and observational design of the study.

CONCLUSIONS

In the last 3 decades, GFR decline has decreased over time in patients enrolled in RCTs who received the standard of care.

TRIAL REGISTRATION

Registered at PROSPERO with record number CRD42022357704.

PLAIN-LANGUAGE SUMMARY

This study evaluated the secular trend in the change in glomerular filtration rate (GFR) decline in the placebo arms of randomized controlled trials (RCTs) that were studying approaches to protect the kidneys in the setting of chronic kidney disease. The placebo groups of RCTs are useful for examining whether the rate of progression of kidney disease has changed over time. We found an improvement in the slope of change in GFR over time. These findings suggest that adherence to standards of kidney care as implemented in clinical trials may be associated with improved clinical outcomes, and these data may inform the design of future RCTs in nephrology.

Personalized Low-Protein Diet Prescription in CKD Population: Merging Evidence From Randomized Trials With Observational Data

Nutritional therapy is a cornerstone of the clinical management of chronic kidney disease (CKD). Nevertheless, randomized controlled trials often have failed to show a relevant benefit of low-protein diets in nonselected CKD populations in terms of slowing the progression of kidney disease and need for dialysis. The more the target population is selected, the less the results can be generalizable to implement in clinical practice. On the contrary, observational studies, especially if performed with patient-centered, flexible approaches, point toward an extensive implementation of dietary protein restriction in different and unselected CKD populations. The observational evidence cannot be disregarded anymore. The most recent guidelines advise implementing low-protein diets or even very-low-protein diets in all CKD patients as early as stage 3. However, the lack of data from large randomized controlled trials on unselected CKD populations as well as on specific subpopulations, such as diabetic or obese patients, which nowadays comprise the majority of CKD subjects, reduces the generalizability of the recommendations. For some patient populations, such as those encompassing very old, nephrotic, or pregnant patients, the literature is even more limited because of the lower prevalence of these conditions and diffused prejudices against reducing protein intake. This pragmatic review discusses the need for integrating information derived from randomized trials with evidence derived from observational studies to guide feasible strategies for more successful implementation of low-protein diets in the treatment of all segments of the CKD population.

Protein restriction for diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) continues to be the leading cause of kidney failure across the world. For decades dietary protein restriction has been proposed for patients with DKD with the aim to retard the progression of chronic kidney disease (CKD) towards kidney failure. However, the relative benefits and harms of dietary protein restriction for slowing the progression of DKD have not been addressed.

OBJECTIVES

To determine the efficacy and safety of low protein diets (LPD) (0.6 to 0.8 g/kg/day) in preventing the progression of CKD towards kidney failure and in reducing the incidence of kidney failure and death (any cause) in adult patients with DKD. Moreover, the effect of LPD on adverse events (e.g. malnutrition, hyperglycaemic events, or health-related quality of life (HRQoL)) and compliance were also evaluated.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 17 November 2022 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs in which adults with DKD not on dialysis were randomised to receive either a LPD (0.6 to 0.8 g/kg/day) or a usual or unrestricted protein diet (UPD) (≥ 1.0 g/kg/day) for at least 12 months.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies and extracted data. Summary estimates of effect were obtained using a random-effects model. Results were summarised as risk ratios (RR) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) or standardised MD (SMD) with 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We identified eight studies involving 486 participants with DKD. The prescribed protein intake in the intervention groups ranged from 0.6 to 0.8 g/kg/day. The prescribed protein intake in the control groups was ≥ 1.0 g/kg/day, or a calculated protein intake ≥ 1.0 g/kg/day if data on prescribed protein intake were not provided. The mean duration of the interventions was two years (ranging from one to five years). Risks of bias in most of the included studies were high or unclear, most notably for allocation concealment, performance and detection bias. All studies were considered to be at high risk for performance bias due to the nature of the interventions. Most studies were not designed to examine death or kidney failure. In low certainty evidence, a LPD may have little or no effect on death (5 studies, 358 participants: RR 0.38, 95% CI 0.10 to 1.44; I² = 0%), and the number of participants who reached kidney failure (4 studies, 287 participants: RR 1.16, 95% CI 0.38 to 3.59; I² = 0%). Compared to a usual or unrestricted protein intake, it remains uncertain whether a LPD slows the decline of glomerular filtration rate over time (7 studies, 367 participants: MD -0.73 mL/min/1.73 m²/year, 95% CI -2.3 to 0.83; I² = 53%; very low certainty evidence). It is also uncertain whether the restriction of dietary protein intake impacts on the annual decline in creatinine clearance (3 studies, 203 participants: MD -2.39 mL/min/year, 95% CI -5.87 to 1.08; I² = 53%). There was only one study reporting 24-hour urinary protein excretion. In very low certainty evidence, a LPD had uncertain effects on the annual change in proteinuria (1 study, 80 participants: MD 0.90 g/24 hours, 95% CI 0.49 to 1.31). There was no evidence of malnutrition in seven studies, while one study noted this condition in the LPD group. Participant compliance with a LPD was unsatisfactory in nearly half of the studies. One study reported LPD had no effect on HRQoL. No studies reported hyperglycaemic events.

AUTHORS' CONCLUSIONS

Dietary protein restriction has uncertain effects on changes in kidney function over time. However, it may make little difference to the risk of death and kidney failure. Questions remain about protein intake levels and compliance with protein-restricted diets. There are limited data on HRQoL and adverse effects such as nutritional measures and hyperglycaemic events. Large-scale pragmatic RCTs with sufficient follow-up are required for different stages of CKD.

Meat intake and risk of mortality and graft failure in kidney transplant recipients

BACKGROUND

It is unknown whether meat intake is beneficial for long-term patient and graft survival in kidney transplant recipients (KTR).

OBJECTIVES

We first investigated the association of the previously described meat intake biomarkers 1-methylhistidine and 3-methylhistidine with intake of white and red meat as estimated from a validated food frequency questionnaire (FFQ). Second, we investigated the association of the meat intake biomarkers with long-term outcomes in KTR.

METHODS

We measured 24-h urinary excretion of 1-methylhistidine and 3-methylhistidine by validated assays in a cohort of 678 clinically stable KTR. Cross-sectional associations were assessed by linear regression. We used Cox regression analyses to prospectively study associations of log2-transformed biomarkers with mortality and graft failure.

RESULTS

Urinary 1-methylhistidine and 3-methylhistidine excretion values were median: 282; interquartile range (IQR): 132-598 µmol/24 h and median: 231; IQR: 175-306 µmol/24 h, respectively. Urinary 1-methylhistidine was associated with white meat intake [standardized β (st β): 0.20; 95% CI: 0.12, 0.28; P < 0.001], whereas urinary 3-methylhistidine was associated with red meat intake (st β: 0.30; 95% CI: 0.23, 0.38; P < 0.001). During median follow-up for 5.4 (IQR: 4.9-6.1) y, 145 (21%) died and 83 (12%) developed graft failure. Urinary 3-methylhistidine was inversely associated with mortality independently of potential confounders (HR per doubling: 0.55; 95% CI: 0.42, 0.72; P < 0.001). Both urinary 1-methylhistidine and urinary 3-methylhistidine were inversely associated with graft failure independent of potential confounders (HR per doubling: 0.84; 95% CI: 0.73, 0.96; P = 0.01; and 0.59; 95% CI: 0.41, 0.85; P = 0.004, respectively).

CONCLUSIONS

High urinary 3-methylhistidine, reflecting higher red meat intake, is independently associated with lower risk of mortality. High urinary concentrations of both 1- and 3-methylhistidine, of which the former reflects higher white meat intake, are independently associated with lower risk of graft failure in KTR. Future intervention studies are warranted to study the effect of high meat intake on mortality and graft failure in KTR, using these biomarkers.

Dietary protein sources and risk of diabetic nephropathy in women: A case-control study

BACKGROUND

Several studies have investigated the association between dietary protein and the risk of diabetic nephropathy (DN); however, there is no agreement on the type of dietary protein sources that might increase the risk of DN. This study was conducted to investigate the associations between different protein sources and the odds of DN developing in Iranian women with existing type 2 diabetes.

METHODS

In this case-control study, 105 women with DN and 105 controls, matched for age and diabetes duration, were selected from the Kowsar Diabetes Clinic in Semnan, Iran. Dietary intake was assessed using a validated and reliable food frequency questionnaire. Dietary protein patterns were estimated using the factor analysis method. Multivariate logistic regression was performed to examine the association between protein patterns and the odds of developing DN.

RESULTS

Two patterns were identified: the Mediterranean-based Dietary Protein Sources (MDPS) pattern which is rich in low-fat dairy, fish, poultry, soy, and legumes, and the Western-based Dietary Protein Sources (WDPS) pattern, rich in red and processed meats, eggs, and high-fat dairy. After adjusting for several confounders, greater adherence (third vs. the first tertile) to the MDPS pattern was associated with lower odds of DN (OR = 0.03; 95 % CI: 0.00, 0.10). In contrast, a strong positive association was observed between adherence to the WDPS pattern and DN (OR = 2.81; 95 % CI: 1.09-7.21).

CONCLUSIONS

Our results show that there is a potential association between the type of protein sources consumed and the odds of DN development in women with type 2 diabetes. Further studies are needed to confirm these findings.

Nutrition in Chronic Kidney Disease-The Role of Proteins and Specific Diets

Chronic kidney disease (CKD) is a global public health burden, needing comprehensive management for preventing and delaying the progression to advanced CKD. The role of nutritional therapy as a strategy to slow CKD progression and uremia has been recommended for more than a century. Although a consistent body of evidence suggest a benefit of protein restriction therapy, patients' adherence and compliance have to be considered when prescribing nutritional therapy in advanced CKD patients. Therefore, these prescriptions need to be individualized since some patients may prefer to enjoy their food without restriction, despite knowing the potential importance of dietary therapy in reducing uremic manifestations, maintaining protein-energy status.

The International Society of Renal Nutrition and Metabolism Commentary on the National Kidney Foundation and Academy of Nutrition and Dietetics KDOQI Clinical Practice Guideline for Nutrition in Chronic Kidney Disease

The Academy of Nutrition and Dietetics and the National Kidney Foundation collaborated to provide an update to the Clinical Practice Guidelines (CPG) for nutrition in chronic kidney disease (CKD). These guidelines provide a valuable update to many aspects of the nutrition care process. They include changes in the recommendations for nutrition screening and assessment, macronutrients, and targets for electrolytes and minerals. The International Society of Renal Nutrition and Metabolism assembled a special review panel of experts and evaluated these recommendations prior to public review. As one of the highlights of the CPG, the recommended dietary protein intake range for patients with diabetic kidney disease is 0.6-0.8 g/kg/day, whereas for CKD patients without diabetes it is 0.55-0.6 g/kg/day. The International Society of Renal Nutrition and Metabolism endorses the CPG with the suggestion that clinicians may consider a more streamlined target of 0.6-0.8 g/kg/day, regardless of CKD etiology, while striving to achieve intakes closer to 0.6 g/kg/day. For implementation of these guidelines, it will be important that all stakeholders work to detect kidney disease early to ensure effective primary and secondary prevention. Once identified, patients should be referred to registered dietitians or the region-specific equivalent, for individualized medical nutrition therapy to slow the progression of CKD. As we turn our attention to the new CPG, we as the renal nutrition community should come together to strengthen the evidence base by standardizing outcomes, increasing collaboration, and funding well-designed observational studies and randomized controlled trials with nutritional and dietary interventions in patients with CKD.

Diabetic Kidney Disease Benefits from Intensive Low-Protein Diet: Updated Systematic Review and Meta-analysis

A dietary protein intake (DPI) of between 0.6 and 0.8 g protein per kilogram body weight per day (g/kg/day) is frequently recommended for adults with moderate-to-advanced chronic kidney disease (CKD). However, evidence on whether patients with diabetic kidney disease (DKD) actually benefit from a DPI of ≤ 0.8 g/kg/day and from a low-protein diet (LPD) at CKD stages 1-3 has not been consistent. We systematically searched MEDLINE, EMBASE, Cochrane Library, Web of Knowledge, as well as the bibliographies of articles identified in the search, for eligible randomized controlled trials that had investigated the effects of LPD (prescribed DPI < 0.8 g/kg/day) versus control diet on the progression of DKD. Nine trials that included 506 participants and follow-up periods varying from 4.5 to 60 months were included in the subsequent systematic review and meta-analysis. The data showed that patients with DKD who consumed < 0.8 g protein/kg/day had a significantly reduced decline in glomerular filtration rate (GFR) (mean difference [MD] 22.31 mL/min/1.73 m², 95% confidence interval [CI] 17.19, 27.42; P  < 0.01) and a significant decrease in proteinuria (standard mean difference [SMD] - 2.26 units, 95% CI - 2.99, - 1.52; P  < 0.001) versus those on the control diet. The benefits of LPD to patients with DKD at CKD stages 1-3 were a markedly decreased proteinuria (SMD - 0.96 units, 95% CI - 1.81, - 0.11; P  = 0.03) and slight but significant decreases in glycated hemoglobin (- 0.42%) and cholesterol levels (- 0.22 mmol/L). Our meta-analysis indicated that a DPI of < 0.8 g/kg/day was strongly associated with a slow decline in GFR and decreased proteinuria in the patients with DKD. Patients with CKD stages CKD 1-3 benefited from LPD in terms of a marked decrease of proteinuria and slight but significant improvements in lipid and glucose control.

Effects of dietary protein intake on renal outcome and mortality in patients with advanced diabetic nephropathy

BACKGROUND

The difficulty of adhering to a low-protein diet is a serious limitation of randomized controlled trials aimed at validating the efficacy of this therapy. In this observational study of patients with diabetic nephropathy, we examined the association of dietary protein intake (DPI) with renal outcome and mortality, taking into account the nutritional status.

METHODS

We conducted a single-center historical cohort study of 449 adult Japanese patients with type 2 diabetes and the urinary albumin-to-creatinine ratio of ≥ 300 mg/g or estimated glomerular filtration rate of < 30 mL/min/1.73 m². DPI was estimated with a formula using nitrogen levels in spot urine and body mass index. Malnutrition was defined as the Geriatric Nutritional Risk Index of ≤ 98. The primary and secondary endpoints were renal replacement therapy (RRT) initiation and mortality before RRT initiation, respectively. The Fine and Gray subdistribution hazard model was used to determine the relative effects of DPI on the respective endpoint.

RESULTS

Decreased DPI was associated with lower incidence of RRT with an adjusted hazard ratio of 0.81 (95% confidence interval: 0.72-0.92, p < 0.001). The interaction between DPI and nutritional status with respect to mortality was significant (p interaction = 0.047). Decreased DPI was a risk factor for mortality in patients with malnutrition (p = 0.009) but not in those without malnutrition (p = 0.559).

CONCLUSIONS

In patients with type 2 diabetic nephropathy, lower DPI was associated with lower incidence of RRT initiation, suggesting beneficial effects of a low-protein diet on kidneys. Conversely, lower DPI might lead to increased mortality in patients with malnutrition.

Safety and effectiveness of low-protein diet supplemented with ketoacids in diabetic patients with chronic kidney disease

BACKGROUND

The impact of the low-protein diet on nutrition in CKD diabetics is uncertain.

METHODS

The metabolic and nutritional effects of a low-protein (0.5-0.6 g/kg/d), normal-high energy (30-35 kcal/kg/d) diet supplemented with ketoacids (LPD-KA) were prospectively evaluated in CKD patients with (DM) and without (non-DM) diabetes mellitus.

RESULTS

197 patients on CKD stages 3-5 were enrolled. DM (n = 81) and non-DM (n = 116) were comparable for gender (Male 58 vs 55%), age (66 ± 9 vs 63 ± 18 years), renal function (eGFR 23 ± 13 vs 24 ± 13 mL/min). After 6-month, serum urea (DM: 131 ± 58 to 105 ± 49 mg/dl, p < 0.05; non-DM: 115 ± 52 to 88 ± 36, p < 0.05) and phosphate (DM: 4.5 ± 1.3 to 4.1 ± 1.2 mg/dl, p = 0.06; non-DM: 4.3 ± 1.0 to 3.7 ± 0.8, p < 0.05) declined. Fasting glucose decreased in DM (126 ± 52 to 103 ± 29 mg/dl, p < 0.05) without insulin dose increase. These effects were preserved after 3-year. Serum albumin did not change after 6 months (DM: 3.7 ± 0.6 to 3.8 ± 0.4 mg/dl; non-DM: 4.0 ± 0.6 to 4.0 ± 0.4) and in the long-term. Body weight (BW) declined after the diet start (DM: 68.9 ± 14.3 to 65.1 ± 12.1 kg, p < 0.05; non-DM: 66.6 ± 15.1 to 64.1 ± 15.1, p < 0.05) and was stable at 6 months and 3 years. Muscle strength at baseline was reduced in all patients and remained stable during the diet period. Changes of nutritional markers during the study were similar among groups and diabetes was not associated to any nutritional change at the multivariate analysis. As attain wasting, lower BMI (< 23 kg/m²) and albumin (< 3.8 g/dl) levels were present in 1/3 patients at start and along 3 years, cholesterol never dropped below the lower threshold (< 100 mg/dl) and poorer FM (< 10%) was less than 10% during the study in both groups.

CONCLUSIONS

In diabetic CKD patients a low-protein diet supplemented with ketoacids improves uremia and diabetes, causes sudden decline of body weight which remains stable over time and has not a negative effect on wasting and muscle mass and fitness. In diabetic CKD patients the LPD-KA is safe and the nutritional impact is the same as in non-diabetics CKD.

Dietary Approaches in the Management of Diabetic Patients with Kidney Disease

Chronic kidney disease (CKD) is one of the most prevalent complications of diabetes, and patients with diabetic kidney disease (DKD) have a substantially higher risk of cardiovascular disease and death compared to their non-diabetic CKD counterparts. In addition to pharmacologic management strategies, nutritional and dietary interventions in DKD are an essential aspect of management with the potential for ameliorating kidney function decline and preventing the development of other end-organ complications. Among DKD patients with non-dialysis dependent CKD, expert panels recommend lower dietary protein intake of 0.8 g/kg of body weight/day, while higher dietary protein intake (>1.2 g/kg of body weight/day) is advised among diabetic end-stage renal disease patients receiving maintenance dialysis to counteract protein catabolism, dialysate amino acid and protein losses, and protein-energy wasting. Carbohydrates from sugars should be limited to less than 10% of energy intake, and it is also suggested that higher polyunsaturated and monounsaturated fat consumption in lieu of saturated fatty acids, trans-fat, and cholesterol are associated with more favorable outcomes. While guidelines recommend dietary sodium restriction to less than 1.5-2.3 g/day, excessively low sodium intake may be associated with hyponatremia as well as impaired glucose metabolism and insulin sensitivity. As patients with advanced DKD progressing to end-stage renal disease may be prone to the "burnt-out diabetes" phenomenon (i.e., spontaneous resolution of hypoglycemia and frequent hypoglycemic episodes), further studies in this population are particularly needed to determine the safety and efficacy of dietary restrictions in this population.

Diet and Diabetic Kidney Disease: Plant Versus Animal Protein

PURPOSE OF REVIEW

The goal of this review is to present an overview of the evidence on the effectiveness of plant-based diets in delaying progression of diabetic kidney disease (DKD).

RECENT FINDINGS

The ideal quantity of dietary protein has been a controversial topic for patients with DKD. Smaller studies have focused on protein source, plant versus animal, for preventing progression. Limited evidence suggests that dietary patterns that focus on plant-based foods, those that are lower in processed foods, or those that are lower in advanced glycation end products (AGE) may be useful in prevention of DKD progression. Increasing plant-based foods, incorporating diet patterns that limit processed foods, or potentially lowering AGE contents in diets may be beneficial for dietary management of DKD. However, dietary studies specifically targeted at DKD treatment are sparse. Further, large trials powered to assess outcomes including changes in kidney function, end-stage kidney disease, and mortality are needed to provide more substantial evidence for these diets.

Nutrition Intervention for Advanced Stages of Diabetic Kidney Disease

IN BRIEF For the goals of reducing diabetic kidney disease (DKD) onset and progression, approaches to nutritional therapy are a subject of much debate. This article discusses selected nutrients that have a role in affecting DKD outcomes and introduces application of newer, individualized concepts for healthful eating, as supported by clinical evidence relevant to patients with DKD. Selected aspects of management of advanced DKD are also reviewed.

Diabetic kidney disease: a report from an ADA Consensus Conference

The incidence and prevalence of diabetes mellitus have grown significantly throughout the world, due primarily to the increase in type 2 diabetes. This overall increase in the number of people with diabetes has had a major impact on development of diabetic kidney disease (DKD), one of the most frequent complications of both types of diabetes. DKD is the leading cause of end-stage renal disease (ESRD), accounting for approximately 50% of cases in the developed world. Although incidence rates for ESRD attributable to DKD have recently stabilized, these rates continue to rise in high-risk groups such as middle-aged African Americans, Native Americans, and Hispanics. The costs of care for people with DKD are extraordinarily high. In the Medicare population alone, DKD-related expenditures among this mostly older group were nearly $25 billion in 2011. Due to the high human and societal costs, the Consensus Conference on Chronic Kidney Disease and Diabetes was convened by the American Diabetes Association in collaboration with the American Society of Nephrology and the National Kidney Foundation to appraise issues regarding patient management, highlighting current practices and new directions. Major topic areas in DKD included 1) identification and monitoring, 2) cardiovascular disease and management of dyslipidemia, 3) hypertension and use of renin-angiotensin-aldosterone system blockade and mineralocorticoid receptor blockade, 4) glycemia measurement, hypoglycemia, and drug therapies, 5) nutrition and general care in advanced-stage chronic kidney disease, 6) children and adolescents, and 7) multidisciplinary approaches and medical home models for health care delivery. This current state summary and research recommendations are designed to guide advances in care and the generation of new knowledge that will meaningfully improve life for people with DKD.

The role of dietary proteins among persons with diabetes

Examining the role of dietary protein and establishing intake guidelines among individuals with diabetes is complex. The 2013 American Diabetes Association (ADA) standards of care recommend an individualized approach to decision making with regard to protein intake and dietary macronutrient composition. Needs may vary based on cardiometabolic risk factors and renal function. Among individuals with impaired renal function, the ADA recommends reducing protein intake to 0.8-1.0 g/kg per day in earlier stages of chronic kidney disease (CKD), and to 0.8 g/kg per day in the later stages of CKD. Epidemiological studies suggest animal protein may increase risk of diabetes; however, few data are available to suggest how protein sources influence diabetes complications.

Low-protein diet for diabetic nephropathy

Diabetic nephropathy is the leading cause of progressive kidney disease, leading to end-stage renal disease and renal replacement therapy. Angiotensin-converting enzyme inhibitors and/or angiotensin receptor blockers have been considered effective at slowing the progression of kidney function deterioration. However, these drugs cannot sufficiently halt the progression of nephropathy to the extent that is required. A low-protein diet (LPD) is believed to be a nutritional intervention that may slow kidney disease progression. In fact, preclinical animal experiments have demonstrated excellent renoprotective effects of an LPD. However, in human clinical trials, analyses of the effects of protein restriction on diabetic nephropathy have not yet revealed consistently positive outcomes of this nutritional intervention. In this review, we analyze the potential renoprotective effects of an LPD on diabetic nephropathy and summarize the outcomes of clinical trials that have systematically investigated the efficacy of an LPD in diabetic nephropathy. In addition, we discuss some potential approaches associated with nutritional interventions to combat progressive kidney disease.

Effect of low-protein diet on kidney function in diabetic nephropathy: meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effect of low-protein diet on kidney function in patients with diabetic nephropathy.

DESIGN

A systematic review and a meta-analysis of randomised controlled trials.

DATA SOURCES

MEDLINE, EMBASE, Cochrane Library, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number (ISRCTN) Register and University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CTR) from inception to 10 December 2012. Internet searches were also carried out with general search engines (Google and Google Scholar).

STUDY SELECTION

Randomised controlled trials that compared low-protein diet versus control diet and assessed the effects on kidney function, proteinuria, glycaemic control or nutritional status.

PRIMARY AND SECONDARY OUTCOME MEASURES AND DATA SYNTHESIS

The primary outcome was a change in the glomerular filtration rate (GFR). The secondary outcomes were changes in proteinuria, post-treatment value of glycated haemoglobin A1C (HbA1c) and post-treatment value of serum albumin. The results were summarised as the mean difference for continuous outcomes and pooled by the random effects model. Subgroup analyses and sensitivity analyses were conducted regarding patient characteristics, intervention period, methodological quality and assessment of diet compliance. The assessment of diet compliance was performed based on the actual protein intake ratio (APIR) of the low-protein diet group to the control group.

RESULTS

We identified 13 randomised controlled trials enrolling 779 patients. A low-protein diet was associated with a significant improvement in GFR (5.82 ml/min/1.73 m(2), 95% CI 2.30 to 9.33, I(2)=92%; n=624). This effect was consistent across the subgroups of type of diabetes, stages of nephropathy and intervention period. However, GFR was improved only when diet compliance was fair (8.92, 95% CI 2.75 to 15.09, I(2)=92% for APIR <0.9 and 0.03, 95% CI -1.49 to 1.56, I(2)=90% for APIR ≥0.9). Proteinuria and serum albumin were not differed between the groups. HbA1c was slightly but significantly decreased in the low-protein diet group (-0.26%, 95% CI -0.35 to -0.18, I(2)=0%; n=536).

CONCLUSIONS

Low-protein diet was significantly associated with improvement of diabetic nephropathy. The adverse effects of low-protein diet were not apparent such as worsening of glycaemic control and malnutrition.

The mean dietary protein intake at different stages of chronic kidney disease is higher than current guidelines

The actual dietary protein intake of adults without and with different stages of chronic kidney disease is not known. To evaluate this we performed cross-sectional analyses of 16,872 adults (20 years of age and older) participating in the National Health and Nutrition Examination Survey 2001-2008 who completed a dietary interview by stage of kidney disease. Dietary protein intake was assessed from 24-h recall systematically collected using the Automated Multiple Pass Method. Complex survey analyses were used to derive population estimates of dietary protein intake at each stage of chronic kidney disease. Using dietary protein intake of adults without chronic kidney disease as the comparator, and after adjusting for age, the mean dietary protein intake was 1.30 g/kg ideal body weight/day (g/kgIBW/d) and was not different from stage 1 or stage 2 (1.28 and 1.25 g/kgIBW/d, respectively), but was significantly different in stage 3 and stage 4 (1.22 and 1.13 g/kgIBW/d, respectively). These mean values appear to be above the Institute of Medicine requirements for healthy adults and the NKF-KDOQI guidelines for stages 3 and 4 chronic kidney disease. Thus, the mean dietary protein intake is higher than current guidelines, even after adjusting for age.

The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults

This article reviews the evidence and nutrition practice recommendations from the American Dietetic Association's nutrition practice guidelines for type 1 and type 2 diabetes in adults. The research literature was reviewed to answer nutrition practice questions and resulted in 29 recommendations. Here, we present the recommendations and provide a comprehensive and systematic review of the evidence associated with their development. Major nutrition therapy factors reviewed are carbohydrate (intake, sucrose, non-nutritive sweeteners, glycemic index, and fiber), protein intake, cardiovascular disease, and weight management. Contributing factors to nutrition therapy reviewed are physical activity and glucose monitoring. Based on individualized nutrition therapy client/patient goals and lifestyle changes the client/patient is willing and able to make, registered dietitians can select appropriate interventions based on key recommendations that include consistency in day-to-day carbohydrate intake, adjusting insulin doses to match carbohydrate intake, substitution of sucrose-containing foods, usual protein intake, cardioprotective nutrition interventions, weight management strategies, regular physical activity, and use of self-monitored blood glucose data. The evidence is strong that medical nutrition therapy provided by registered dietitians is an effective and essential therapy in the management of diabetes.

Randomized controlled trial of nutritional counseling on body composition and dietary intake in severe CKD

BACKGROUND

Progressive loss of kidney function results in an increased risk of malnutrition. Despite this, there is little evidence informing the impact of nutrition intervention on predialysis patients with chronic kidney disease (CKD; stages 4 and 5).

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

56 outpatients (men, 62%; mean age, 70.7 +/- 14.0 [SD] years) with CKD were randomly allocated to intervention (n = 29) or control (n = 27) by using a concealed computer-generated sequence.

INTERVENTION

The intervention group, provided with individualized dietary counseling with regular follow-up aimed at achieving an intake of 0.8 to 1.0 g/kg of protein and greater than 125 kJ/kg of energy, or control, receiving written material only.

OUTCOMES & MEASURES

Change in body composition (body cell mass, measured by means of total-body potassium, in 40 of 56 participants), nutritional status (Subjective Global Assessment), and energy and protein intake (3-day food record).

RESULTS

During the 12 weeks, the intervention group had 3.5% (95% confidence interval, -2.1 to 9.1) less decrease in body cell mass, 17.7-kJ/kg/d (95% confidence interval, 8.2 to 27.2) greater increase in energy intake, greater improvement in Subjective Global Assessment (P < 0.01), and no significant difference in protein intake compared with the control group (-0.04 g/kg/d; 95% confidence interval, -0.73 to 0.16). The intervention was associated with greater increases in energy and protein intake in women than men (interaction P < 0.001 for both).

LIMITATIONS

Power to detect change in body cell mass, potential bias in ascertainment of Subjective Global Assessment.

CONCLUSIONS

In predialysis patients with CKD, structured nutrition intervention had a greater effect on energy and protein intake in women than men. Additional investigations are warranted to determine the impact on body composition.

Protein restriction for diabetic renal disease

BACKGROUND

Diabetic renal disease (diabetic nephropathy) is a leading cause of end-stage renal failure. Once the process has started, it cannot be reversed by glycaemic control, but progression might be slowed by control of blood pressure and protein restriction.

OBJECTIVES

To assess the effects of dietary protein restriction on the progression of diabetic nephropathy in patients with diabetes.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE, ISI Proceedings, Science Citation Index Expanded and bibliographies of included studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and before and after studies of the effects of a modified or restricted protein diet on diabetic renal function in people with type 1 or type 2 diabetes following diet for at least four months were considered.

DATA COLLECTION AND ANALYSIS

Two reviewers performed data extraction and evaluation of quality independently. Pooling of results was done by means of random-effects model.

MAIN RESULTS

Twelve studies were included, nine RCTs and three before and after studies. Only one study explored all-cause mortality and end-stage renal disease (ESRD) as endpoints. The relative risk (RR) of ESRD or death was 0.23 (95% confidence interval (CI) 0.07 to 0.72) for patients assigned to a low protein diet (LPD). Pooling of the seven RCTs in patients with type 1 diabetes resulted in a non-significant reduction in the decline of glomerular filtration rate (GFR) of 0.1 ml/min/month (95% CI -0.1 to 0.3) in the LPD group. For type 2 diabetes, one trial showed a small insignificant improvement in the rate of decline of GFR in the protein-restricted group and a second found a similar decline in both the intervention and control groups. Actual protein intake in the intervention groups ranged from 0.7 to 1.1 g/kg/day. One study noted malnutrition in the LPD group. We found no data on the effects of LPDs on health-related quality of life and costs.

AUTHORS' CONCLUSIONS

The results show that reducing protein intake appears to slightly slow progression to renal failure but not statistically significantly so. However, questions concerning the level of protein intake and compliance remain. Further longer-term research on large representative groups of patients with both type 1 and type 2 diabetes mellitus is necessary. Because of the variability amongst patients, there might perhaps be a six month therapeutic trial of protein restriction in all individuals, with continuation only in those who responded best. Trials are required of different types of protein.

Dietary advice for treatment of type 2 diabetes mellitus in adults

BACKGROUND

While initial dietary management immediately after formal diagnosis is an 'accepted' cornerstone of treatment of type 2 diabetes mellitus, a formal and systematic overview of its efficacy and method of delivery is not currently available.

OBJECTIVES

To assess the effects of type and frequency of different types of dietary advice for adults with type 2 diabetes.

SEARCH STRATEGY

We carried out a comprehensive search of The Cochrane Library, MEDLINE, EMBASE, CINAHL, AMED, bibliographies and contacted relevant experts.

SELECTION CRITERIA

All randomised controlled trials, of six months or longer, in which dietary advice was the main intervention.

DATA COLLECTION AND ANALYSIS

The lead investigator performed all data extraction and quality scoring with duplication being carried out by one of the other six investigators independently with discrepancies resolved by discussion and consensus. Authors were contacted for missing data.

MAIN RESULTS

Thirty-six articles reporting a total of eighteen trials following 1467 participants were included. Dietary approaches assessed in this review were low-fat/high-carbohydrate diets, high-fat/low-carbohydrate diets, low-calorie (1000 kcal per day) and very-low-calorie (500 kcal per day) diets and modified fat diets. Two trials compared the American Diabetes Association exchange diet with a standard reduced fat diet and five studies assessed low-fat diets versus moderate fat or low-carbohydrate diets. Two studies assessed the effect of a very-low-calorie diet versus a low-calorie diet. Six studies compared dietary advice with dietary advice plus exercise and three other studies assessed dietary advice versus dietary advice plus behavioural approaches. The studies all measured weight and measures of glycaemic control although not all studies reported these in the articles published. Other outcomes which were measured in these studies included mortality, blood pressure, serum cholesterol (including LDL and HDL cholesterol), serum triglycerides, maximal exercise capacity and compliance. The results suggest that adoption of regular exercise is a good way to promote better glycaemic control in type 2 diabetic patients, however all of these studies were at high risk of bias.

AUTHORS' CONCLUSIONS

There are no high quality data on the efficacy of the dietary treatment of type 2 diabetes, however the data available indicate that the adoption of exercise appears to improve glycated haemoglobin at six and twelve months in people with type 2 diabetes. There is an urgent need for well-designed studies which examine a range of interventions, at various points during follow-up, although there is a promising study currently underway.

The suppressive effects of dietary protein restriction on the progression of renal impairment in OLETF rats

BACKGROUND

The suppressive effect of dietary protein restriction on the progression of diabetic nephropathy remains controversial. We investigated the effects of protein and energy restrictions on both albuminuria and morphology using diabetic-prone Otsuka Long-Evans Tokushima fatty (OLETF) rats.

METHODS

In this study, male OLETF rats were divided into two groups according to their energy intake. They were then further divided into three subgroups based on their amount of dietary protein, which ranged between 10% and 30% of their total intake. Urinary albumin excretion (UAE) was used as a marker of renal impairment, and body weight fasting (F) and postchallenge (P), blood glucose (BG) levels, and systolic blood pressure (SBP) were all measured during various experimental periods up to 28 weeks of age.

RESULTS

The OLETF rats fed with the high-calorie diet started to gain weight at 12 weeks, and their FBG and PBG were elevated at 22 weeks, while SBP did not differ between the two groups. In addition, UAE increased significantly in the rats fed with the high-calorie diet. However, the increasing rates of UAE with age were higher in the rats with a higher protein diet within the same energy groups. UAE correlated well with the amounts of dietary energy and protein at 16 and 28 weeks of age, while it correlated with both the FBG and PBG at only 28 weeks of age. A linear regression analysis, using the data obtained at 28 weeks, showed that the amount of protein intake and FBG explained 63.4% and 23.9% of the variation in UAE, respectively. Histological studies revealed that protein and energy restriction markedly reduced the sclerotic changes of the glomeruli.

CONCLUSION

Dietary protein restriction starting very early in the life of OLETF rats, in combination with energy restriction, clearly suppressed UAE and the typical morphological changes that otherwise occurred at around 16 weeks of age. This method also seemed to be more effective than energy restriction alone in slowing down any increase in UAE. The influence of BG levels on UAE was lower at an early age, while it became an increasingly important factor at later ages in the experimental rat model.

A low-carbohydrate diet may prevent end-stage renal failure in type 2 diabetes. A case report

An obese patient with type 2 diabetes whose diet was changed from the recommended high-carbohydrate, low-fat type to a low-carbohydrate diet showed a significant reduction in bodyweight, improved glycemic control and a reversal of a six year long decline of renal function. The reversal of the renal function was likely caused by both improved glycemic control and elimination of the patient's obesity. Insulin treatment in type 2 diabetes patients usually leads to weight increase which may cause further injury to the kidney. Although other unknown metabolic mechanisms cannot be excluded, it is likely that the obesity caused by the combination of high-carbohydrate diet and insulin in this case contributed to the patient's deteriorating kidney function. In such patients, where control of bodyweight and hyperglycemia is vital, a trial with a low-carbohydrate diet may be appropriate to avoid the risk of adding obesity-associated renal failure to already failing kidneys.

A randomized trial of low-protein diet in type 1 and in type 2 diabetes mellitus patients with incipient and overt nephropathy

OBJECTIVE

The efficacy of a low-protein diet in the secondary prevention of diabetic nephropathy is not established in patients with type 1 or type 2 diabetes mellitus. To determine whether a low-protein diet slows the decrease in glomerular filtration rate (GFR) and decreases the albumin excretion rate (AER) in diabetic patients with incipient and overt nephropathy, we performed a 2-year prospective, randomized controlled trial comparing the effects of a low-protein diet (0.8 g/kg/day) with a usual-protein diet.

SETTING AND PATIENTS

The study was conducted in a University hospital and included 63 type 1 and type 2 diabetic patients with either incipient or overt nephropathy and mild renal failure (prestudy GFR, 80 +/- 20 mL/min). The primary outcome measures were decreased in GFR and 24-hour AER.

RESULTS

In the low-protein-diet group, patients were younger (52 +/- 12 versus 63 +/- 9 years old) and more often were type 2 diabetic. During the follow-up period, according to dietary records the low-protein-diet group consumed 16% +/- 3% of total caloric intakes as compared with 19% +/- 4% in the usual-protein-diet group (P < .02), but 24-hour urinary urea excretions did not differ between the two groups. The 2-year GFR decrease was 7 +/- 11 mL/min in the low-protein-diet group and 5 +/- 15 mL/min in the usual-protein-diet group (P = not significant). AER did not increase significantly in the two diet groups during the follow-up period. Blood pressure and glycemic control were similar in the two groups all along the study. The decrease in GFR and AER were also similar in 6 compliant patients according to dietary records and to 24-hour urinary urea excretions from the low-protein-diet group and in 12 patients from the usual-protein-diet group.

CONCLUSIONS

A 2-year low-protein diet did not alter the course of GFR or of AER in diabetic patients with incipient or overt nephropathy receiving renin-angiotensin blockers with strict blood pressure control.

Evaluation of epidemiologic evidence on the role of nutrition in the development of diabetes and its complications

This article evaluates the body of epidemiologic evidence on the effects of nutritional factors in diabetes development published within the past 5 years (2000-2004), considering strengths and weaknesses of specific studies, as well as of various study designs in general. Furthermore, this article aims to determine whether clinical practice and public health practice guidelines should, or should not, be determined based on the totality of available scientific evidence.

[The role of the diet as a risk factor for the development and progression of diabetic nephropathy]

Diabetic nephropathy (DN) is the leading cause of kidney disease in patients starting renal replacement therapy, and affects up to 40% of type 1 and type 2 diabetic patients. Diet seems to play an important role in the development of the disease. There are evidences supporting the concept that not only the amount but also the origin of dietary protein are associated with DN. Few studies analyzed the role of dietary lipids. A low-protein diet slows down the decline of renal function and ameliorates the DN prognosis and death in patients with type 1 diabetes with micro- and macroalbuminuria. Studies in type 2 diabetic patients are scanty but short-term studies suggest that this approach decreases albuminuria. However, the use of low-protein diet for long periods is compromised by poor compliance and its long-term safety is not firmly established. Enthusiastic results come up when comparing the effect of different sources of animal protein on renal function and lipid profile in patients with DN, which may represent an alternative strategy for low-protein diet on medical nutritional therapy in patients with DN and in cardiovascular risk factors and endothelial function.

Effects of an angiotensin II receptor blocker, valsartan, on residual renal function in patients on CAPD

BACKGROUND

Both residual renal function and blood pressure (BP) control contribute to patient survival in patients receiving continuous ambulatory peritoneal dialysis (CAPD). It is unknown whether antihypertensive drugs affect residual renal function in addition to BP reduction.

METHODS

We examined the effects of an angiotensin II receptor blocker, valsartan, on residual renal function and total clearance (renal and peritoneal) in 34 Japanese CAPD patients from 3 months to 2 years after the start of dialysis therapy. Patients were randomly assigned to valsartan (n = 18; age, 63.5 +/- 3.7 years; 11 men, 7 women) or a control group (n = 16; age, 63.5 +/- 3.3 years; 10 men, 6 women). Conventional antihypertensive treatment was continued in all patients to achieve the target BP in both groups of 130/80 mm Hg or less, measured at home.

RESULTS

BP reduction was similar in the valsartan and control groups. Valsartan significantly slowed the progressive decline in both residual renal function (3.2 +/- 0.3 to 4.3 +/- 0.7 mL/min/1.73 m2) and total clearance (42.1 +/- 3.2 to 48.3 +/- 4.8 L/wk/1.73 m2) by dialysis in CAPD patients compared with controls (5.9 +/- 0.5 to 2.8 +/- 0.4 mL/min/1.73 m2; 47.1 +/- 4.8 to 31.4 +/- 5.2 L/wk/1.73 m2).

CONCLUSION

This study shows that in patients with hypertension starting CAPD therapy, valsartan slows the decline in residual renal function and contributes to maintenance of weekly creatinine clearance and Kt/V (fraction per dialysis), which are the major factors contributing to the mortality and morbidity of CAPD patients. This effect appears to be mostly a result of maintaining residual renal function.

Nutrition therapy for diabetic nephropathy

Human observational studies report no association between protein intakes less than 20% of energy intake and the development of renal disease. With protein intakes greater than 20% of energy intake there is an association between protein with increased albumin excretion rate. Once albuminuria is present, intervention studies suggest a beneficial effect on renal function with a reduction of protein to 0.8 to 1.0 g/kg/d with microalbuminuria and to 0.8 g/kg/d with macroalbuminuria. Restriction of sodium to 2400 mg/d or possibly for some to 2000 mg/d assists in the control of hypertension. In macroalbuminuria, there may be additional benefits in lowering phosphorus intake to 500 to 1000 mg/d. There is no strong evidence to suggest benefit from vegetable or plant proteins over animal protein, but there is evidence for benefit on renal function, glucose, lipids, and blood pressure from weight-maintaining diets meeting guidelines for a healthy diet.