Protein restriction, glomerular filtration rate and albuminuria in patients with type 2 diabetes mellitus: a randomized trial

Effects of a Low-Protein Diet on Kidney Function in Patients With Chronic Kidney Disease: An Umbrella Review of Systematic Reviews and Meta-analyses of Randomized Controlled Trials

CONTEXT

Chronic kidney disease (CKD) stands out as one of the most widespread diseases globally. Dietary interventions, such as adopting a low-protein diet (LPD), play a crucial role as a key approach in impeding the advancement of CKD.

OBJECTIVE

The objective of this umbrella review was to provide understanding into the effects of an LPD on kidney function among individuals with CKD, along with evaluating the certainty of the available evidence.

DATA SOURCES

Searches for relevant studies were conducted without limitations through databases such as PubMed, Scopus, Web of Science, and Google Scholar, encompassing findings up to June 2023.

DATA EXTRACTION

The effect sizes for each meta-analysis were recalibrated using a random-effects model. The certainty of the evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

DATA ANALYSIS

Twenty-five meta-analyses including 47 randomized controlled trials were included in this study. Moderate certainty of the evidence suggests that LPDs may reduce glycated hemoglobin (HbA1c) and phosphorus levels, and the risk of progressing to end-stage renal disease in patients with CKD. Moreover, notable outcomes include increased glomerular filtration rate and decreased levels of serum albumin, blood urea nitrogen, and bicarbonate, although the certainty of evidence is low. In addition, LPDs can substantially decrease proteinuria, urine urea, and parathyroid hormone (PTH), although with very low certainty. The effects on serum creatinine, calcium, systolic blood pressure, and diastolic blood pressure are statistically nonsignificant, with the certainty of evidence ranging from low to moderate.

CONCLUSION

LPDs demonstrated beneficial effects on renal function in patients with CKD, which is supported by moderate to very low certainty evidence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023473647.

Chronic Kidney Disease in the Older Adult Patient with Diabetes

Diabetes mellitus (DM) and chronic kidney disease (CKD) are common in middle aged and older adult individuals. DM may accelerate the aging process, and the age-related declines in the estimated glomerular filtration rate (eGFR) can pose a challenge to diagnosing diabetic kidney disease (DKD) using standard diagnostic criteria especially with the absence of severe albuminuria among older adults. In the presence of CKD and DM, older adult patients may need multidisciplinary care due to susceptibility to various health issues, e.g., cognitive decline, auditory or visual impairment, various comorbidities, complex medical regimens, and increased sensitivity to medication adverse effects. As a result, it can be challenging to apply recent therapeutic advancements for the general population to older adults. We review the evidence that the benefits from these newer therapies apply equally to older and younger patients with CKD and diabetes type 2 and propose a comprehensive management. This framework will address nonpharmacological measures and pharmacological management with renin angiotensin system inhibitors (RASi), sodium glucose co-transporter 2 inhibitors (SGLT2i), non-steroidal mineralocorticoids receptor antagonists (MRAs), and glucagon like peptide 1 receptor agonists (GLP1-RAs).

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.

Impact of low-protein diet on cardiovascular risk factors and kidney function in diabetic nephropathy: A systematic review and meta-analysis of randomized-controlled trials

AIM

To assess the efficacy of low-protein diets (LPD) on cardiovascular risk factors and kidney function in diabetic nephropathy (DN) based on randomized controlled trials (RCTs).

METHODS

A comprehensive systematic search was undertaken in PubMed/MEDLINE, Web of Science, SCOPUS and Embase databases from inception until January 2022 without using time or language restrictions. RCTs which reported the effects of LPD on cardiovascular risk factors and kidney function in DN were considered.

RESULTS

The results of the present study showed that a LPD significantly reduces urinary urea (WMD: -244.49 g/day, 95 % CI: -418.83, -70.16, P = 0.006) and HbA1c (WMD: -0.20, 95 % CI: -0.39, -0.01, P = 0.036) levels. However, the results did not show neither significant nor beneficial effect on other renal function and cardiovascular risk factors. Furthermore, the results of subgroup analysis showed LPD caused a further decrease in HbA1c during the follow-up period of ≤ 24 weeks, protein intake less than 0.8 g/kg/d and in individuals younger than 50 years. Albuminuria also showed a greater reduction in people under the age of 50 with type 1 diabetes (DMT1) following a LPD.

CONCLUSION

The results of the present study showed that LPD significantly reduces urinary urea and HbA1c.

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.

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.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Efficacy of low-protein diet in diabetic nephropathy: a meta-analysis of randomized controlled trials

Purpose

We aimed to systematically assess the efficacy of low-protein diet preventing progression of diabetic nephropathy based on randomized controlled trials (RCTs).

Methods

A systematic and electronic search was conducted. Initial searches of literature updated to September 2018 were made using the following databases including CNKI, VIP, Wanfang, Cochrane, PubMed, and Embase using the index words for qualified RCTs. Additional searches were performed to identify linked literature sources. Data of RCTs on low-protein diet versus control diet, efficacy analysis of kidney function, nutritional status or proteinuria were extracted. Random effects model and fixed effects model were applied to combine the data which were further analyzed by Chi-squared test and I²tests. The main outcomes were then analyzed through the use of relative risks (RR), mean difference (MD) and its 95% confidence interval (95% CI).

Results

Twenty articles were included in the present meta-analysis with a total of 690 patients in the low-protein diet group (LPD) and a total of 682 patients in the control group. Moderate to strong evidence indicated that LPD was significantly effective for decreasing the urinary albumin excretion rate (SMD:0.62, 95%CI:0.06–1.19) and proteinuria (SMD:0.69, 95%CI:0.22–1.16) versus the control group. No statistical difference, however, was found in glycosylated hemoglobin (SMD:0.17, 95%CI:-0.18–0.51), serum creatinine (SMD:0.20, 95%CI:-0.26–0.66), as well as glomerular filtration rate (SMD:0.21, 95%CI:-0.29–0.71) between the two groups.

Conclusion

The current meta-analysis reveals an effective role of low-protein diet in improving diabetic nephropathy. However, the small number of involved patients may limit the accuracy of results. High-quality RCTs with a larger sample size in the future are required to confirm the current findings.

Efficacy of low-protein diet for diabetic nephropathy: a systematic review of randomized controlled trials

Background

A low-protein diet (LPD) is believed to be beneficial in slowing the progression of kidney disease. It is reported that low protein diet can improve protein, sugar and lipid metabolism, and reduce the symptoms and complications of renal insufficiency. However, there has been controversial regarding the effects of protein restriction on diabetic nephropathy (DN).

Objective

To investigate the efficacy of LPD on renal function in patients with type 1 or 2 DN by meta-analysis of randomized controlled trials (RCTs).

Design

PubMed, MEDLINE, EMBASE and China National Knowledge Infrastructure databases were searched. Eleven randomized controlled trials met the inclusion criteria, of which 10 were English and 1 was Chinese. The primary outcome was a change in glomerular filtration rate (GFR). The secondary outcome was a change in proteinuria. Random-effects models were used to calculate the standardized mean difference (SMD) and the corresponding 95% confidence intervals (CI). Subgroup analyses were also performed.

Results

Our research indicated that LPD was not associated with a significant improvement in GFR (1.59 ml · min⁻¹ · 1.73 m⁻², 95% CI -0.57, 3.75, I² = 76%; p = 0.15). This effect was consistent across the subgroups regardless of type of diabetes, course of diabetes and intervention period. Our results also showed that there was no significant difference on improvement of proteinuria in patients of LPD and those in normal-protein diet groups (− 0.48, 95%CI-1.70, 0.74, I² = 94%, p = 0.44). Subgroup analysis revealed that LPD resulted in increased excretion of proteinuria in patients with type 2 diabetes (1.32, 95% CI 0.17, 2.47, I² = 86%, p = 0.02).

Conclusion

The present research showed that LPD was not significantly associated with improvement of renal function in patients with either type 1 or 2 diabetic nephropathy. Although these results do not completely eliminate the possibility that LPD is beneficial for patients with diabetic nephropathy, it does not seem to be significant benefit to renal function.

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.

Dietary interventions to contrast the onset and progression of diabetic nephropathy: A critical survey of new data

This article is a critical overview of recent contributions on the dietary corrections and the foods that have been claimed to delay or hinder the onset of diabetic nephropathy (DN) and its progression to end-stage renal disease. Innovative dietary and behavioral approaches to the prevention and therapy of DN appear to be the most captivating in consideration of the rather well-established protocols for glucose and blood pressure control in use. In addition to restricted caloric intake to contrast obesity and the metabolic syndrome, adjustments in the patient's macronutrients intake, and in particular some degree of reduction in protein, have been long considered in the prevention of DN progression. More recently, the focus has shifted to the source of proteins and the content of glycotoxins in the diet as well as to the role of specific micronutrients. Few clinical trials have specifically addressed the role of those micronutrients associated with diet proteins that show the most protective effect against DN. Research on clinical outcome and mechanisms of action of such micronutrients appears the most promising in order to develop both effective intervention on nutritional education of the patient and selection of functional foods capable of contrasting the onset and progression of DN.

Correlations of dietary energy and protein intakes with renal function impairment in chronic kidney disease patients with or without diabetes

Dietary energy and protein intake can affect progression of chronic kidney disease (CKD). CKD complicated with diabetes is often associated with a decline in renal function. We investigated the relative importance of dietary energy intake (DEI) and dietary protein intake (DPI) to renal function indicators in nondiabetic and diabetic CKD patients. A total of 539 Stage 3-5 CKD patients [estimated glomerular filtration rate (eGFR)<60 mL/min/1.73 m² using the Modification of Diet in Renal Disease equation] with or without diabetes were recruited from outpatient clinics of Nephrology and Nutrition in a medical center in Taiwan. Appropriateness of DEI and DPI was used to subcategorize CKD patients into four groups:(1) kidney diet (KD) A (KD-A), the most appropriate diet, was characterized by low DPI and adequate DEI; (2) KD-B, low DPI and inadequate DEI; (3) KD-C, excess DPI and adequate DEI; and (4) KD-D, the least appropriate diet, excess DPI and inadequate DEI. Inadequate DEI was defined as a ratio of actual intake/recommended intake less than 90% and adequate DEI as over 90%. Low DPI was defined as less than 110% of recommended intake and excessive when over 110%. Outcome measured was eGFR. In both groups of CKD patients, DEI was significantly lower (p<0.001) and DPI higher (p=0.002) than recommended levels. However, only in the nondiabetic CKD patients were KD-C and KD-D significantly correlated with reduced eGFR compared with KD-A at increments of -5.63 mL/min/1.73 m² (p = 0.029) and -7.72 mL/min/1.73 m² (p=0.015). In conclusion, inadequate energy and excessive protein intakes appear to correlate with poorer renal function in nondiabetic CKD patients. Patients with advanced CKD are in need of counseling by dietitians to improve adherence to diets.

Protein Diet Restriction Slows Chronic Kidney Disease Progression in Non-Diabetic and in Type 1 Diabetic Patients, but Not in Type 2 Diabetic Patients: A Meta-Analysis of Randomized Controlled Trials Using Glomerular Filtration Rate as a Surrogate

BACKGROUND/OBJECTIVE

Studies, including various meta-analyses, on the effect of Protein Diet Restriction on Glomerular Filtration Rate (GFR) in Chronic Kidney Disease (CKD) have reported conflicting results. In this paper, we have provided an update on the evidence available on this topic. We have investigated the reasons why the effect has been inconsistent across studies. We have also compared the effect on GFR in various subgroups including type 1 diabetics, type 2 diabetics and non-diabetics.

METHOD

We searched for Randomized Controlled Trials on this intervention from MEDLINE, EMBASE, and other information sources. The PRISMA guidelines, as well as recommended meta-analysis practices were followed in the selection process, analysis and reporting of our findings. The effect estimate used was the change in mean GFR. Heterogeneity across the considered studies was explored using both subgroup analyses and meta-regression. Quality assessment was done using the Cochrane risk of bias tool and sensitivity analyses.

RESULTS

15 randomized controlled trials, including 1965 subjects, were analyzed. The pooled effect size, as assessed using random-effects model, for all the 15 studies was -0.95 ml/min/1.73m2/year (95% CI: -1.79, -0.11), with a significant p value of 0.03. The combined effect estimate for the non-diabetic and type 1 diabetic studies was -1.50 ml/min/1.73m2/year (95% CI: -2.73, -0.26) with p value of 0.02. The effect estimate for the type 2 diabetic group was -0.17 ml/min/1.73m2/year (95% CI: -1.88, 1.55) with p value of 0.85. There was significant heterogeneity across the included studies (I2 = 74%, p value for Q < 0.0001), explained by major variations in the percentage of type 2 diabetic subjects, the number of subjects and overall compliance level to diet prescribed.

CONCLUSION

Our findings suggest that protein diet restriction slows chronic renal disease progression in non-diabetic and in type 1 diabetic patients, but not in type 2 diabetic patients.

Impact of Lifestyle Modification on Diabetic Kidney Disease

Kidney disease is common in patients with type 1 and type 2 diabetes mellitus and is associated with adverse health outcomes, including progression to end-stage renal disease. In the general population, adherence to a healthy lifestyle is known to reduce the risk of cardiovascular events and death. Among individuals with diabetic kidney disease, modifications in lifestyle factors, including diet, physical activity, smoking habits, and body mass index, represent a promising cost-effective therapeutic adjunct to pharmacologic treatment of kidney disease incidence and progression.

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.

Ketogenic diet for obesity: friend or foe?

Obesity is reaching epidemic proportions and is a strong risk factor for a number of cardiovascular and metabolic disorders such as hypertension, type 2 diabetes, dyslipidemia, atherosclerosis, and also certain types of cancers. Despite the constant recommendations of health care organizations regarding the importance of weight control, this goal often fails. Genetic predisposition in combination with inactive lifestyles and high caloric intake leads to excessive weight gain. Even though there may be agreement about the concept that lifestyle changes affecting dietary habits and physical activity are essential to promote weight loss and weight control, the ideal amount and type of exercise and also the ideal diet are still under debate. For many years, nutritional intervention studies have been focused on reducing dietary fat with little positive results over the long-term. One of the most studied strategies in the recent years for weight loss is the ketogenic diet. Many studies have shown that this kind of nutritional approach has a solid physiological and biochemical basis and is able to induce effective weight loss along with improvement in several cardiovascular risk parameters. This review discusses the physiological basis of ketogenic diets and the rationale for their use in obesity, discussing the strengths and the weaknesses of these diets together with cautions that should be used in obese patients.

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.

Nutrition therapy recommendations for the management of adults with diabetes

There is no standard meal plan or eating pattern that works universally for all people with diabetes. In order to be effective, nutrition therapy should be individualized for each patient/client based on his or her individual health goals; personal and cultural preferences; health literacy and numeracy; access to healthful choices; and readiness, willingness, and ability to change. Nutrition interventions should emphasize a variety of minimally processed nutrient dense foods in appropriate portion sizes as part of a healthful eating pattern and provide the individual with diabetes with practical tools for day-to-day food plan and behavior change that can be maintained over the long term.

Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets

Very-low-carbohydrate diets or ketogenic diets have been in use since the 1920s as a therapy for epilepsy and can, in some cases, completely remove the need for medication. From the 1960s onwards they have become widely known as one of the most common methods for obesity treatment. Recent work over the last decade or so has provided evidence of the therapeutic potential of ketogenic diets in many pathological conditions, such as diabetes, polycystic ovary syndrome, acne, neurological diseases, cancer and the amelioration of respiratory and cardiovascular disease risk factors. The possibility that modifying food intake can be useful for reducing or eliminating pharmaceutical methods of treatment, which are often lifelong with significant side effects, calls for serious investigation. This review revisits the meaning of physiological ketosis in the light of this evidence and considers possible mechanisms for the therapeutic actions of the ketogenic diet on different diseases. The present review also questions whether there are still some preconceived ideas about ketogenic diets, which may be presenting unnecessary barriers to their use as therapeutic tools in the physician's hand.

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.

Light and shadows of dietary protein restriction in elderly with chronic kidney disease

Approximately 45% of the elderly population suffers from chronic kidney disease (CKD). The onset and the course of CKD can be ameliorated to a significant degree by several interventions, such as lowering blood pressure and serum lipid levels and achieving optimal glucose control in diabetes. In elderly patients with more advanced CKD, additional treatment may be needed. In these patients, a low-protein diet (LPD) regimen may delay the need for dialysis therapy. However, in the elderly, feasibility and compliance to LPD could be difficult and its effects are uncertain. In this contribution, we discuss the usefulness and the barriers of LPD regimen in the elderly.

Nutrition and acne: therapeutic potential of ketogenic diets

The influence of nutrition on skin health is a growing research area but the findings of various studies on the effect of diet on the development of acne have often been contradictory. The general opinion among researchers has oscillated between two different, opposing positions: that diet either is or is not a key factor for acne development. This review examines the evidence supporting an influence of various dietary components on the development of acne particularly focusing on the role played by carbohydrates. The physiological and biochemical effects of the ketogenic diet are examined from this perspective and mechanisms will be proposed via which this type of diet could have a role in the treatment of acne.

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.

Diabetic nephropathy

Diabetic nephropathy is the leading cause of chronic renal disease and a major cause of cardiovascular mortality. Diabetic nephropathy has been categorized into stages: microalbuminuria and macroalbuminuria. The cut-off values of micro- and macroalbuminuria are arbitrary and their values have been questioned. Subjects in the upper-normal range of albuminuria seem to be at high risk of progression to micro- or macroalbuminuria and they also had a higher blood pressure than normoalbuminuric subjects in the lower normoalbuminuria range. Diabetic nephropathy screening is made by measuring albumin in spot urine. If abnormal, it should be confirmed in two out three samples collected in a three to six-months interval. Additionally, it is recommended that glomerular filtration rate be routinely estimated for appropriate screening of nephropathy, because some patients present a decreased glomerular filtration rate when urine albumin values are in the normal range. The two main risk factors for diabetic nephropathy are hyperglycemia and arterial hypertension, but the genetic susceptibility in both type 1 and type 2 diabetes is of great importance. Other risk factors are smoking, dyslipidemia, proteinuria, glomerular hyperfiltration and dietary factors. Nephropathy is pathologically characterized in individuals with type 1 diabetes by thickening of glomerular and tubular basal membranes, with progressive mesangial expansion (diffuse or nodular) leading to progressive reduction of glomerular filtration surface. Concurrent interstitial morphological alterations and hyalinization of afferent and efferent glomerular arterioles also occur. Podocytes abnormalities also appear to be involved in the glomerulosclerosis process. In patients with type 2 diabetes, renal lesions are heterogeneous and more complex than in individuals with type 1 diabetes. Treatment of diabetic nephropathy is based on a multiple risk factor approach, and the goal is retarding the development or progression of the disease and to decrease the subject's increased risk of cardiovascular disease. Achieving the best metabolic control, treating hypertension (<130/80 mmHg) and dyslipidemia (LDL cholesterol <100 mg/dl), using drugs that block the renin-angiotensin-aldosterone system, are effective strategies for preventing the development of microalbuminuria, delaying the progression to more advanced stages of nephropathy and reducing cardiovascular mortality in patients with diabetes.

Gender-specific reference value of urine albumin-creatinine ratio in healthy Chinese adults: results of the Beijing CKD survey

BACKGROUND

The reference value of urine albumin-creatinine ratio (ACR) has racial disparities. The ACR reference value in a healthy Beijing population is reported.

METHODS

A reference Beijing population was sampled via a multistage, clustered complex sampling method. By excluding subjects with self-reported kidney disease, hypertension, diabetes, dyslipidemia, cardiovascular disease, obesity or underweight condition, overt proteinuria, hematuria, or pyuria, as well as those with an estimated glomerular filtration rate (eGFR) > 200ml/min/1.73m2 or < 60ml/min/1.73m2, apparently healthy subjects (1260 males, 2305 females, aged 18-84y) were selected to be included in the current analysis. Urine albumin was measured using the immunoturbidimetic method, creatinine was measured using Jaffe's kinetic method on a morning spot-urine sample, and ACR was calculated. The 95th percentile of ACR was used as the normal upper limit. The association between ACR and each of gender, age, systolic blood pressure, body mass index, serum glucose, lipids, and eGFR was examined.

RESULTS

The normal upper limit of ACR was 14mg/g (1.58mg/mmol) for males and 20mg/g (2.26mg/mmol) for females. Females had higher ACR values than males, and age, systolic blood pressure, and eGFR were positively correlated with ACR.

CONCLUSIONS

The ACR reference value in the healthy Beijing population is lower than that of the Western population. Age, systolic blood pressure, and eGFR were found to correlate with ACR.

Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials

BACKGROUND

A low-protein diet (LPD) has been proposed for many years to delay the progression of diabetic nephropathy. However, the efficacy of an LPD with respect to renal outcome is disputed.

OBJECTIVE

We aimed to determine the effect of an LPD on renal function in patients with type 1 or 2 diabetic renal diseases by using a meta-analysis of randomized controlled trials.

DESIGN

Medline, EMBASE, and the Cochrane Central Register of Controlled Trials were searched. Eight studies met the inclusion criteria for our meta-analysis: a duration of >6 mo, use of a randomized control group, availability of outcome data for changes in glomerular filtration rate (GFR) or creatinine clearance rate (CCR), and albuminuria or proteinuria in patients with type 1 or 2 diabetic nephropathy. Data were combined by means of a fixed-effects model. Weighted mean differences (WMD) were calculated for the change in GFR or CCR, glycated hemoglobin (HbA(1c)), and serum albumin between the LPD and control groups. A random-effects model was also used to calculate the standardized mean difference for the change in urinary albumin excretion or proteinuria.

RESULTS

Overall, a change in WMD for GFR or CCR was not significantly associated with an LPD, but a decrease in WMD for HbA(1c) was significant in the LPD group (P = 0.005). Although the benefit of LPD therapy on proteinuria was significant (P = 0.003), great heterogeneity was observed. In a subgroup analysis, LPD resulted in lower serum albumin concentrations.

CONCLUSION

LPD was not associated with a significant improvement of renal function in patients with either types 1 or 2 diabetic nephropathy.

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.

Nutritional status in patients with diabetes and chronic kidney disease: a prospective study

BACKGROUND

A poor nutritional status reduces the life expectancy of diabetes patients undergoing hemodialysis.

OBJECTIVE

The study objective was to specify the nutritional outcome in patients with chronic kidney disease (CKD) and well-controlled diabetes.

DESIGN

Forty-five diabetes patients with CKD were enrolled in a cooperative-care program designed to control glucose, blood pressure, LDL cholesterol, and the albumin excretion rate (AER). Their glomerular filtration rate (GFR), body composition, serum albumin (SA), and resting energy expenditure were assessed and compared at baseline and 2 y later.

RESULTS

Thirty-five patients did not start dialysis. Their glycated hemoglobin, blood pressure, LDL cholesterol, and AER improved; their GFR declined slowly (-3.3 mL x min(-1) x 1.73 m(-2) x y(-1)). Their body mass index (BMI), lean body mass, and SA increased. The GFR decline was correlated negatively with the initial BMI (r = -0.37, P < 0.05) and positively with the initial GFR (r = 0.34, P < 0.05). Ten patients started hemodialysis: except for higher total body water (P < 0.05) and extracellular volume (P < 0.01), their initial nutritional status did not differ significantly from that of 10 patients with comparable baseline severe CKD but without dialysis. At the second evaluation, patients on hemodialysis lost lean body mass, and their SA was lower than that of the patients with severe CKD (P = 0.05); lean body mass was unchanged and SA was higher (P = 0.01) in the patients with severe CKD. No significant difference was detected for resting energy expenditure.

CONCLUSIONS

Nutritional status improved in CKD patients with well-controlled diabetes without dialysis, and it deteriorated in patients who started dialysis. A high initial BMI was associated with a slower decline in GFR.