Dietary fiber, kidney function, inflammation, and mortality risk

The relationship between dietary inflammatory index (DII) and early renal injury in population with/without hypertension: analysis of the National health and nutrition examination survey 2001-2002

BACKGROUND

Inflammation plays a crucial role in occurrence of kidney injury, and specific dietary patterns can influence systemic inflammation levels. However, the relationship between dietary inflammatory potential and early-stage kidney damage remains unclear.

METHOD

2,108 participants was recruited from 2001-2002 National Health and Nutrition Examination Survey (NHANES). Dietary Inflammatory Index (DII) is utilized to assess dietary inflammatory potential, calculated through a 24-h dietary recall questionnaire. Early renal injury was evaluated using urinary albumin to creatinine (UACR), cystatin C (CysC), β-2 microglobulin (β2M), and estimated glomerular filtration rate (eGFR) based on serum creatinine (eGFRs), cystatin C (eGFRc), and both Scr and CysC (eGFRs&c). Participant characteristics were analyzed, and association between DII, hypertension, and early renal injury markers was explored using multiple linear and logistic regression models.

RESULTS

The average age of participants was 53.9 years. DII exhibited a positive correlation with UACR (β = -0.048[0.017,0.078]), β2M (β = 0.019[0.010,0.027]), CysC (β = 0.012 [0.004,0.021]). Conversely, a negative correlation was observed between DII and eGFRc (β = -1.126[-1.554, -0.699]), eGFRs&c (β=-1.101[-1.653, -0.549]). A significant association was observed between hypertension and abnormality of early kidney damage markers. Subgroup analysis reveals that the positive correlation between DII and the occurrence of abnormal markers of early kidney damage is only observed in individuals with hypertension. Furthermore, an interaction between DII and hypertension was detected in eGFRs&c (OR:1.250[1.042, 1.499], p for interaction = 0.03).

CONCLUSION

Higher levels of DII may be associated with occurrence of early kidney damage. For individuals with hypertension, avoiding excessive consumption of pro-inflammatory foods may reduce the risk of renal injury.

Unravelling the Link between the Gut Microbiome and Autoimmune Kidney Diseases: A Potential New Therapeutic Approach

The gut microbiota and short chain fatty acids (SCFA) have been associated with immune regulation and autoimmune diseases. Autoimmune kidney diseases arise from a loss of tolerance to antigens, often with unclear triggers. In this review, we explore the role of the gut microbiome and how disease, diet, and therapy can alter the gut microbiota consortium. Perturbations in the gut microbiota may systemically induce the translocation of microbiota-derived inflammatory molecules such as liposaccharide (LPS) and other toxins by penetrating the gut epithelial barrier. Once in the blood stream, these pro-inflammatory mediators activate immune cells, which release pro-inflammatory molecules, many of which are antigens in autoimmune diseases. The ratio of gut bacteria Bacteroidetes/Firmicutes is associated with worse outcomes in multiple autoimmune kidney diseases including lupus nephritis, MPO-ANCA vasculitis, and Goodpasture's syndrome. Therapies that enhance SCFA-producing bacteria in the gut have powerful therapeutic potential. Dietary fiber is fermented by gut bacteria which in turn release SCFAs that protect the gut barrier, as well as modulating immune responses towards a tolerogenic anti-inflammatory state. Herein, we describe where the current field of research is and the strategies to harness the gut microbiome as potential therapy.

Associations of dietary inflammatory index with low estimated glomerular filtration rate, albuminuria and chronic kidney disease in U.S adults: Results from the NHANES 2011-2018

BACKGROUND AND AIMS

Chronic Kidney Disease (CKD) is characterized by a high inflammation status with ever-increasing prevalence, and defined as low estimated glomerular filtration rate (eGFR) or albuminuria. Both low eGFR and albuminuria can have independent effects on the body. The dietary inflammatory index (DII) is a validated tool used to assess the inflammatory potential of the diet. We aim to explore not only the association between DII and CKD, but also the associations of DII with low eGFR and albuminuria, respectively. In addition, their associations in different subgroups remain to be explored.

METHODS AND RESULTS

18,070 participants from the 2011-2018 NHANES with complete data of dietary intake and laboratory data were involved in our study. The data of 24-hour dietary recall interview was used to calculate DII, CKD could be reflected by laboratory data of creatinine and albumin. Then weighted multivariate logistic regression models and subgroup analyses were performed. The prevalence of low eGFR, albuminuria and CKD were 6.8%, 9.8% and 14.5%, respectively. A positive association between DII and low eGFR was observed (OR=1.12, 95%CI: 1.05-1.21), Q2, Q3 and Q4 are positively associated with a significant 39%, 65% and 71% increased risk of low eGFR compared with Q1 (P for trend<0.05). DII was also associated with CKD (OR=1.06, 95%CI: 1.01-1.11).

CONCLUSION

Significant positive associations of DII with CKD and low eGFR were observed. But we didn't find such association between DII and albuminuria.

Relationship between dietary fiber to carbohydrate ratio and mortality risk in US adults: NHANES 2007-2018

BACKGROUND AND AIMS

The evidence is inconsistent regarding associations between relative proportions of macronutrient intake and disease risk, potentially due to limitations in accounting for differential effects of simple sugars and dietary fiber, grouped as "carbohydrates." We examined the association between the ratio of dietary fiber to carbohydrate intake (FC-R) measure, the relative proportion of macronutrients, and mortality risk in a nationally representative sample of U.S. adults.

METHODS AND RESULTS

We performed a retrospective cohort study, using data from the National Health and Nutrition Examination Survey in 2007-2018 and linked mortality data among 15,789 adults aged ≥40 years. We categorized participants into three groups by tertile cutpoints of FC-R, and by percent calories from carbohydrate (<45 %, 45-65 %, and >65 %). Cox proportional hazards regression was performed to estimate hazard ratios (HR) for all-cause mortality with 95 % confidence intervals (95 % CI), adjusting for demographic, health history, and lifestyle factors. During a median follow-up of 6.5 years, 2044 deaths were observed. Compared to the low FC-R group, higher FC-R groups showed a reduction in mortality risk after adjusting for potential confounders (high vs low: HR = 0.71, 95 % CI = 0.62-0.83). The association persisted in those consuming 45-65 % and >65 % of calories from carbohydrate, while the association was attenuated in those with <45 % of calories from carbohydrate. Percent calories from carbohydrate showed no association with mortality risk.

CONCLUSION

Higher FC-R was associated with lower all-cause mortality risk in adults with moderate to high levels of percent calories from carbohydrate. Mechanisms of the association warrant further investigation.

Dietary inflammatory index is associated with Vitamin D in CKD patients

OBJECTIVES

Multiple observational studies have shown that low serum level of 25-hydroxyvitamin D (25(OH)D) in patients with chronic kidney disease (CKD) have been associated with a faster progression of kidney disease and a higher risk of all-cause mortality. We aim to assess the association between dietary inflammatory index (DII) with Vitamin D in adults with CKD.

METHOD

The National Health and Nutrition Examination Survey appropriated participants from 2009 to 2018 were enrolled. The patients who were under the age of 18, pregnant, and having incomplete data were excluded. DII score were calculated based on a single 24-h dietary recall interview for each participant. Mutivariable regression analysis and subgroup analysis were utilized to determine the independent associations between vitamin D with DII in CKD patients.

RESULTS

In total, 4283 individuals were finally included. The results showed a negative association between DII scores and 25(OH)D with statistical significance (β =  - 1.83, 95% CI  - 2.31,  - 1.34, P < 0.001). In subgroup analysis stratified by gender, low eGFR, age and diabetes, the negative association between DII scores and 25(OH)D was still significant (all P for trend < 0.05). The results from interacion test indicated that the magnitude of the association was the same for the population with and without low eGFR (P for interacion = 0.464).

CONCLUSION

Higher consumption of pro-inflammatory diet correlates negatively with the 25(OH)D level in CKD patients with and without low eGFR. Anti-inflammatory diet management may reduce the reduction of vitamin D in CKD patients.

Dietary fiber intake and all-cause and cause-specific mortality: An updated systematic review and meta-analysis of prospective cohort studies

BACKGROUND

Accumulating evidence supports the effects of dietary fiber on the risk of non-communicable diseases (NCDs). However, there is no updated systematic review and meta-analysis that compares and pools the effect of different types of fiber on mortality.

METHODS

In this systematic review and meta-analysis, all prospective cohort studies that evaluated the relationship between dietary fiber intake and all-cause or cause-specific mortality were included. The PubMed, SCOPUS, and Web of Science databases were searched up to October 2022. Data extraction and quality assessment were performed by two researchers independently. Heterogeneity between studies was assessed using Chi-square based test. Random/fixed effect meta-analysis was used to pool the hazard ratios (HR) or relative risks (RR) and 95 % confidence intervals (CI) for the association between different types of fiber and mortality.

RESULTS

This systematic review included 64 eligible studies, with a total sample size of 3512828 subjects, that investigated the association between dietary fiber intake and mortality from all-cause, cardiovascular disease (CVD), and cancer. Random-effect meta-analysis shows that higher consumption of total dietary fiber, significantly decreased the risk of all-cause mortality, CVD-related mortality, and cancer-related mortality by 23, 26 and 22 % (HR:0.77; 95%CI (0.73,0.82), HR:0.74; 95%CI (0.71,0.77) and HR:0.78; 95%CI (0.68,0.87)), respectively. The consumption of insoluble fiber tended to be more effective than soluble fiber intake in reducing the risk of total mortality and mortality due to CVD and cancer. Additionally, dietary fiber from whole grains, cereals, and vegetables was associated with a reduced risk of all-cause mortality, while dietary fiber from nuts and seeds reduced the risk of CVD-related death by 43 % (HR:0.57; 95 % CI (0.38,0.77)).

CONCLUSION

This comprehensive meta-analysis provides additional evidence supporting the protective association between fiber intake and all-cause and cause-specific mortality rates.

Changes in Dietary Nutrient Intake and Estimated Glomerular Filtration Rate over a 5-Year Period in Renal Transplant Recipients

The scarcity of dietary guidance for renal transplant recipients (RTRs) raises concerns regarding obesity and associated comorbidities, including impaired renal function. This two-stage cross-sectional study examined longitudinal changes in dietary nutrient intake in the same individuals over a 5-year interval. This study involved two stages: T1 (September 2016 to June 2018) and T2 (July 2022 to August 2023). The average duration between the two data collection stages was 6.17 ± 0.42 (range 5.20-6.87) years. The study included 227 RTRs with an average age and time since transplant of 49.97 ± 12.39 and 9.22 ± 7.91 years, respectively. Of the 35 patients who participated in both phases, fewer than half met the recommended intakes for energy, dietary fiber, and most vitamins and minerals, as set in the Dietary Reference Intakes (DRIs) or by the Dietitian Association Australia (DAA). Over half exceeded the DRI recommended intake for total protein, and more than 80% of the protein consumed per kilogram of body weight exceeded the DAA's recommendations. In the T2 stage, the RTRs had a significantly higher blood urea nitrogen level, lower albumin level, and estimated glomerular filtration rate. These findings indicate that deteriorating dietary intake in RTRs can adversely affect their nutritional status and transplanted kidney function over a 5-year period.

Total and different dietary fiber subtypes and the risk of all-cause, cardiovascular, and cancer mortality: a dose-response meta-analysis of prospective cohort studies

We aimed to conduct a comprehensive review of the association between dietary fiber and the risk of mortality. We did a systematic search in PubMed, Scopus, and Web of Science up to November 2022 to find prospective cohort studies of the relationship between total and subtypes of dietary fiber and the risk of all-cause, cardiovascular (CVD), and cancer mortality in the general population. The hazard ratios (HRs) and 95% CIs were calculated using a random-effects model. A total of 28 studies with 1 613 885 participants were included. Higher intake of total and subtypes of dietary fiber including cereal, vegetable, legume, soluble, and insoluble fiber, but not fruit fiber, was associated with a lower risk of all-cause mortality, with HRs ranging from 0.77 for insoluble fiber to 0.93 for legume fiber. Similar findings were observed for CVD mortality, where higher intake of total and all subtypes of dietary fiber was each associated with a lower risk. Higher intake of total, cereal, vegetable, and insoluble fiber was also associated with a lower risk of cancer mortality. No association was found between the intake of fruit, legume, and soluble fiber and cancer mortality. Dose-response meta-analyses suggested an inverse association between total fiber intake and the risk of all-cause, CVD, and cancer mortality. The certainty of evidence was rated moderate for the association of total fiber with all-cause, CVD, and cancer mortality. In conclusion, our findings highlight the potential advantages of consuming a wide range of dietary fiber subtypes against all-cause, CVD, and cancer mortality. Registry and registry number: PROSPERO (CRD42021226816).

Associations between ultra-processed food consumption and kidney function in an older adult population with metabolic syndrome

BACKGROUND & AIMS

Ultra-processed food (UPF) consumption has increased dramatically over the last decades worldwide. Although it has been linked to some cardiometabolic comorbidities, there is limited evidence regarding kidney function. This study aimed to cross-sectionally and longitudinally assess the association between UPF consumption and estimated-glomerular filtration rate (eGFR) based on Cystatin C (CysC).

METHODS

Older adults (mean age 65 ± 5.0 years, 46% women) with overweight/obesity and metabolic syndrome (MetS) who had available data of CysC at baseline (n = 1909), at one-year and at 3-years of follow-up (n = 1700) were analyzed. Food consumption was assessed using a validated 143-item semi-quantitative food frequency questionnaire and UPF consumption (% of g/d) at baseline and changes after one-year of follow-up were estimated according to NOVA classification system. Multivariable-adjusted linear and logistic regression models were performed to evaluate the cross-sectional associations between UPF consumption with eGFR levels and decreased kidney function (eGFR <60 ml/min/1.73 m2) at baseline. Multivariable-adjusted mixed-effects linear regression models were fitted to investigate the associations between one-year changes in UPF and eGFR over 3-years of follow-up.

RESULTS

Individuals with the highest baseline UPF consumption showed lower eGFR (β: -3.39 ml/min/1.73 m2; 95% CI: -5.59 to -1.20) and higher odds of decreased kidney function (OR: 1.64; 95% CI: 1.21 to 2.22) at baseline, compared to individuals in the lowest tertile. Participants in the highest tertile of one-year changes in UPF consumption presented a significant decrease in eGFR after one-year of follow-up (β: -1.45 ml/min/1.73 m2; 95% CI: -2.90 to -0.01) as well as after 3-years of follow-up (β: -2.18 ml/min/1.73 m2; 95% CI: -3.71 to -0.65) compared to those in the reference category.

CONCLUSIONS

In a Mediterranean population of older adults with overweight/obesity and MetS, higher UPF consumption at baseline and one-year changes towards higher consumption of UPF were associated with worse kidney function at baseline and over 3-years of follow-up, respectively.

CLINICAL TRIAL REGISTRY NUMBER

ISRCTN89898870.

Dietary intake of total vegetable, fruit, cereal, soluble and insoluble fiber and risk of all-cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies

Objectives

To conduct a systematic review and meta-analysis of prospective cohort studies to investigate the association between total, vegetable, fruit, cereal, soluble and insoluble fiber intake and risk of all causes, cardiovascular disease (CVD), and cancer mortality and quantitatively assess the dose-response relation.

Methods

Eligible studies were identified by searching PubMed, Embase and Web of science before August 2023. Random effects models were used to calculate summary relative risk (RR) and 95% confidence intervals (CI) and restricted cubic splines to model the linear/non-linear association.

Results

The summary RR for all-cause, CVD and cancer mortality of dietary fiber was 0.90 (95% CI: 0.86,0.93), 0.87 (0.84,0.91), 0.91 (0.88,0.93), respectively. Significant association was observed for all-cause and CVD mortality with fruit, vegetable cereal and soluble fiber intake and cancer mortality with cereal fiber intake. No significant association was found for insoluble fiber, vegetable or fruit fiber intake and cancer mortality. Dose-response analysis showed a significant non-linear relation of dietary fiber intake with all-cause mortality, and linear relation for others.

Conclusions

Higher dietary fiber including different type and food sources of fiber intake were associated with lower risk of mortality. Our findings provide more comprehensive evidence on dietary fiber intake with mortality.

Systematic review registration

https://www.crd.york.ac.uk/prospero, identifier: CRD42022338837.

The Role of Plant-Based Diets in Preventing and Mitigating Chronic Kidney Disease: More Light than Shadows

Chronic kidney disease (CKD) is a non-communicable disease that affects >10% of the general population worldwide; the number of patients affected by CKD is increasing due in part to the rise in risk factors such as obesity, hypertension, and diabetes mellitus. As many studies show, diet can be an important tool for preventing and mitigating the onset of non-communicable diseases. Plant-based diets (PBDs) are those that emphasize the consumption of plant foods and may or may not include small or moderate amounts of animal foods. Recently, these diets have received increasing interest because they have been associated with favourable effects on health and also appear to protect against the development and progression of CKD. PBDs, which are associated with protein restrictions, seem to offer adjunctive advantages in patients with chronic kidney disease, as compared to conventional low-protein diets that include animal proteins. The principal aims of this review are to provide a comprehensive overview of the existing literature regarding the role of plant-based diets and low-protein, plant-based diets in the context of chronic kidney disease. Moreover, we try to clarify the definition of plant-based diets, and then we analyse possible concerns about the use of PBDs in patients with chronic kidney disease (nutritional deficiency and hyperkalaemia risk). Finally, we offer some strategies to increase the nutritional value of plant-based low-protein diets. In the Materials and Methods section, many studies about plant-based diets and low-protein plant-based diets (e.g., the very-low-protein diet and vegan low-protein diet, LPD) in chronic kidney disease were considered. In the Results and Conclusion section, current data, most from observational studies, agree upon the protective effect of plant-based diets on kidney function. Moreover, in patients with advanced CKD, low-protein plant-based options, especially a very-low-protein diet supplemented with heteroanalogues (VLPDs), compared to a conventional LPD appear to offer adjunctive advances in terms of delaying dialysis and mitigating metabolic disturbances. However, further studies are necessary to better investigate the possible metabolic and cardiovascular advantages of plant-based LPDs versus conventional LPDs.

Association of Three Different Dietary Approaches to Stop Hypertension Diet Indices with Renal Function in Renal Transplant Recipients

Several dietary indices assess the impacts of the Dietary Approaches to Stop Hypertension (DASH) diet on health outcomes. We explored DASH adherence and renal function among 85 Taiwanese renal transplant recipients (RTRs) in a cross-sectional study. Data collection included demographics, routine laboratory data, and 3-day dietary records. Three separate DASH indices, that defined by Camões (based on nine nutrients), that defined by Fung (using seven food groups and sodium), and that modified by Fung (as above but separated for men and women) were used. Renal function was ascertained through the estimated glomerular filtration rate (eGFR) from patients' medical records. Participants' mean age was 49.7 ± 12.6 years and eGFR was 54.71 ± 21.48 mL/min/1.73 m2. The three established DASH diet indices displayed significant correlations (r = 0.50-0.91) and indicated the nutritional adequacy of the diet. Multiple linear regressions indicated a significant positive association between higher DASH scores for each index and increased eGFR. In addition, RTRs in the highest DASH score tertile had higher eGFR rates than those in the lowest tertile, regardless of confounding variables. Adherence to a DASH-style diet correlated with better renal function among RTRs. Educating RTRs about the DASH diet may prevent graft function deterioration.

The benefits of dietary fiber: the gastrointestinal tract and beyond

Dietary fiber is considered an essential constituent of a healthy child's diet. Diets of healthy children with adequate dietary fiber intake are characterized by a higher diet quality, a higher nutrient density, and a higher intake of vitamins and minerals in comparison to the diets of children with poor dietary fiber intake. Nevertheless, a substantial proportion of children do not meet the recommended dietary fiber intake. This is especially true in those children with kidney diseases, as traditional dietary recommendations in kidney diseases have predominantly focused on the quantities of energy and protein, and often restricting potassium and phosphate, while overlooking the quality and diversity of the diet. Emerging evidence suggests that dietary fiber and, by extension, a plant-based diet with its typically higher dietary fiber content are just as important for children with kidney diseases as for healthy children. Dietary fiber confers several health benefits such as prevention of constipation and fewer gastrointestinal symptoms, reduced inflammatory state, and decreased production of gut-derived uremic toxins. Recent studies have challenged the notion that a high dietary fiber intake confers an increased risk of hyperkalemia or nutritional deficits in children with kidney diseases. There is an urgent need of new studies and revised guidelines that address the dietary fiber intake in children with kidney diseases.

Low-protein diet supplemented with inulin lowers protein-bound toxin levels in patients with stage 3b-5 chronic kidney disease: a randomized controlled study

Introduction

Objective: this study aimed to evaluate whether low-salt low-protein diet (LPD) supplemented with 10 g of inulin could lower serum toxin levels in patients with chronic kidney disease (CKD), thereby providing evidence for adjusting dietary prescriptions of inhospital patients and outpatient nutrition consultants. Methods: we randomized 54 patients with CKD into two groups. Dietary protein intake compliance was evaluated using a 3-day dietary diary and 24-h urine nitrogen levels. The primary outcomes were indoxyl sulfate (IS) and p-cresyl sulfate (PCS), and secondary outcomes included inflammation marker levels, nutritional status, and renal function. We assessed 89 patients for eligibility, and a total of 45 patients completed the study, including 23 and 22 in the inulin-added and control groups, respectively. Results: PCS values decreased in both groups after intervention: inulin-added group, ∆PCS -1.33 (-4.88, -0.63) μg/mL vs. LPD group, -4.7 (-3.78, 3.69) μg/mL (p = 0.058). PCS values reduced from 7.52 to 4.02 μg/mL (p < 0.001) in the inulin-added group (p < 0.001). Moreover, IS decreased from 3.42 (2.53, 6.01) μg/mL to 2.83 (1.67, 4.74) μg/mL after adding inulin; ∆IS was -0.64 (-1.48, 0.00) μg/mL, and a significant difference was observed compared with the control group (p = 0.004). The inflammation index decreased after intervention. Conclusion: dietary fiber supplementation may reduce serum IS and PCS levels and modulate their inflammatory status in predialysis CKD patients.

The Ideal Diet for Humans to Sustainably Feed the Growing Population - Review, Meta-Analyses, and Policies for Change

INTRODUCTION

As of now, no study has combined research from different sciences to determine the most suitable diet for humans. This issue is urgent due to the predicted population growth, the effect of this on the environment, and the deterioration of human health and associated costs.

METHODS

A literature review determined whether an optimal diet for humans exists and what such a diet is, followed by six meta-analyses. The standard criteria for conducting meta-analyses of observational studies were followed. A review of literature reporting Hazard Ratios with a 95% confidence interval for red meat intake, dairy intake, plant-based diet, fiber intake, and serum IGF-1 levels were extracted to calculate effect sizes.

RESULTS

Results calculated using NCSS software show that high meat consumption increases mortality probability by 18% on average and increases diabetes risk by 50%. Plant-based and high-fiber diets decrease mortality by 15% and 20% respectively ( p < .001). Plant-based diets decreased diabetes risk by 27%, and dairy consumption (measured by increased IGF-1 levels) increased cancer probability by 48% ( p < 0.01). A vegetarian or Mediterranean diet was not found to decrease the probability of heart disease. A vegetarian diet can be healthy or not, depending on the foods consumed. A Mediterranean diet with high quantities of meat and dairy products will not produce the health effects desired. The main limitations of the study were that observational studies were heterogeneous and limited by potential confounders.

DISCUSSION

The literature and meta-analyses point to an optimal diet for humans that has followed our species from the beginnings of humankind. The optimal diet is a whole food, high fiber, low-fat, 90+% plant-based diet. This diet allowed humans to become the most developed species on Earth. To ensure people's nutritional needs are met healthily and sustainably, governmental dietary interventions are necessary.

Plant or Animal-Based or PLADO Diets: Which Should Chronic Kidney Disease Patients Choose?

Nutrition therapy is the cornerstone treatment for chronic kidney disease (CKD). Although much attention has been given to dietary protein intake in CKD patients, many findings now demonstrate that the type of dietary protein intake may be more critical for CKD patients. In protein bioavailability and malnutrition prevention, many physicians recommend that CKD patients adhere to a low protein diet and restrict their plant foods, such as vegetables, fruits, and soybeans. However, nephrologists should not ignore the potential benefits of plant foods for CKD patients. It is not advisable to restrict the intake of plant foods in the later stage of CKD simply to prevent the development of hyperkalemia and malnutrition. This article highlights the benefits and possible problems of a plant-dominant low protein diet (PLADO) diet, defined as an LPD with dietary protein intake of 0.6-0.8 g/kg/day with at least 50% plant-based source for CKD patients. We hope to provide new opinions for clinical work and CKD patients.

The Role of Dietary Potassium in the Cardiovascular Protective Effects of Plant-Based Diets

Dietary intervention is an essential factor in managing a multitude of chronic health conditions such as cardiovascular and chronic kidney disease. In recent decades, there has been a host of research suggesting the potential benefit of plant-based diets in mitigating the health outcomes of these conditions. Plant-based diets are rich in vegetables and fruits, while limiting processed food and animal protein sources. The underlying physiological mechanism involves the interaction of several macronutrients and micronutrients such as plant protein, carbohydrates, and dietary potassium. Specifically, plant-based foods rich in potassium provide cardiorenal protective effects to include urinary alkalization and increased sodium excretion. These diets induce adaptive physiologic responses that improve kidney and cardiovascular hemodynamics and improve overall metabolic health. A shift toward consuming plant-based diets even in subjects with cardiorenal decrements may reduce their morbidity and mortality. Nonetheless, randomized controlled trials are needed to confirm the clinical benefits of plant-based diets.

Association between Fiber Intake and Risk of Incident Chronic Kidney Disease: The UK Biobank Study

OBJECTIVES

Dietary fiber intake is associated with a lower risk of diabetes, cardiovascular disease, and cancer. However, it is unknown whether dietary fiber has a beneficial effect on preventing the development of chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Using the UK Biobank prospective cohort, 110,412 participants who completed at least one dietary questionnaire and had an estimated glomerular filtration rate ≥60 mL/min/1.73 m2, urinary albumin-to-creatinine ratio <30 mg/g, and no history of CKD were included. The primary exposure was total dietary fiber density, calculated by dividing the absolute amount of daily total fiber intake by total energy intake (g/1,000 kcal). We separately examined soluble and insoluble fiber densities as additional predictors. The primary outcome was incident CKD based on diagnosis codes.

RESULTS

A total of 3,507 (3.2%) participants developed incident CKD during a median follow-up of 9.9 years. In a multivariable cause-specific model, the adjusted hazard ratios (aHRs; 95% confidence intervals [CIs]) for incident CKD were 0.85 (0.77-0.94), 0.78 (0.70-0.86), and 0.76 (0.68-0.86), respectively, for the second, third, and highest quartiles of dietary fiber density (reference: lowest quartile). In a continuous model, the aHR for each +∆1.0g/1,000 kcal increase in dietary fiber density was 0.97 (95% CI, 0.95-0.99). This pattern of associations was similar for both soluble and insoluble fiber densities and did not differ across subgroups of sex, age, body mass index, hypertension, diabetes, smoking, and inflammation.

CONCLUSION

Increased fiber intake was associated with a lower risk of CKD in this large well-characterized cohort.

Gut-kidney axis in IgA nephropathy: Role on mesangial cell metabolism and inflammation

IgA Nephropathy (IgAN) is the commonest primary glomerular disease around the world and represents a significant cause of end-stage renal disease. IgAN is characterized by mesangial deposition of IgA-immune complexes and mesangial expansion. The pathophysiological process includes an abnormally glycosylated IgA1, which is an antigenic target. Autoantibodies specifically recognize galactose-deficient IgA1 forming immune complexes that are amplified in size by the soluble IgA Fc receptor CD89 leading to deposition in the mesangium through interaction with non-classical IgA receptors. The local production of cytokines promotes local inflammation and complement system activation, besides the stimulation of mesangial proliferation. The spectrum of clinical manifestations is quite variable from asymptomatic microscopic hematuria to rapidly progressive glomerulonephritis. Despite all the advances, the pathophysiology of the disease is still not fully elucidated. The mucosal immune system is quoted to be a factor in triggering IgAN and a "gut-kidney axis" is proposed in its development. Furthermore, many recent studies have demonstrated that food intake interferes directly with disease prognosis. In this review, we will discuss how mucosal immunity, microbiota, and nutritional status could be interfering directly with the activation of intrinsic pathways of the mesangial cells, directly resulting in changes in their function, inflammation and development of IgAN.

Association Between Ultraprocessed Food Consumption and Risk of Incident CKD: A Prospective Cohort Study

RATIONALE & OBJECTIVE

Ultraprocessed foods have become readily available in the global food supply in the past few decades. Several adverse health outcomes have been linked with higher consumption of ultraprocessed foods. However, the impact of ultraprocessed foods on chronic kidney disease (CKD) risk remains unknown.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

14,679 middle-aged adults without CKD at baseline in the Atherosclerosis Risk in Communities (ARIC) study.

EXPOSURE

Ultraprocessed foods consumption (servings per day) calculated using dietary data collected via a food frequency questionnaire at visit 1 and visit 3.

OUTCOME

Incident CKD defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 accompanied by ≥25% eGFR decline, CKD-related hospitalization or death, or kidney failure with kidney replacement therapy.

ANALYTICAL APPROACH

Multivariable-adjusted Cox proportional hazards models were used to assess the association between ultraprocessed foods consumption and CKD. Restricted cubic splines were used to examine the shape of the association.

RESULTS

During a median follow-up period of 24 years, there were 4,859 cases of incident CKD. The incidence rate for the highest quartile of ultraprocessed foods consumption was 16.5 (95% CI, 15.6-17.4) per 1,000 person-years and 14.7 (95% CI, 13.9-15.5) per 1,000 person-years for the lowest quartile of consumption. After adjusting for a range of confounders including lifestyle factors, demographic characteristics, and health behaviors, participants in the highest quartile of ultraprocessed foods consumption had a 24% higher risk (HR, 1.24 [95% CI, 1.15-1.35]) of developing CKD compared with those in the lowest quartile. There was an approximately linear relationship observed between ultraprocessed food intake and risk of CKD. By substituting 1 serving of ultraprocessed foods with minimally processed foods, there was a 6% lower risk of CKD observed (HR, 0.94 [95% CI, 0.93-0.96]; P < 0.001).

LIMITATIONS

Self-reported data and residual confounding.

CONCLUSIONS

Higher ultraprocessed foods consumption was independently associated with a higher risk of incident CKD in a general population.

Fibre Intake in Chronic Kidney Disease: What Fibre Should We Recommend?

Chronic kidney disease (CKD) is a major global health problem that challenges all patients' healthcare needs. Fibre consumption benefits kidney patients by acting preventively on associated risk factors, improving intestinal microbiota composition or reducing metabolic acidosis and inflammation. In this review, we focus on increasing fibre consumption and the quality of fibre to recommend, in addition to increasing the consumption of foods that naturally have it in their design, that can resort to fortified foods or fibre supplements. The Western nutritional practice, which is low in fibre and rich in animal proteins, saturated fats, sodium, and sugar, increases the risk of mortality in these patients. On the contrary, patterns with higher consumption of fibre and vegetable proteins, such as the Mediterranean, vegetarian, or Plant dominant low protein diet (PLADO), seem to have a preventive effect on the associated risk factors and influence CKD progression. Until now, the use of fibre supplements has not achieved an evident impact on clinical results. Fibre-rich foods contain other nutrients that reduce cardiovascular risk. Promoting diets richer in vegetables and guaranteeing adequate energy and protein intake is a challenge for the multidisciplinary teams involved in the standard of care for CKD.

Dose-response relationship between dietary inflammatory index and diabetic kidney disease in US adults

OBJECTIVE

The impact of the dietary potential inflammatory effect on diabetic kidney disease (DKD) has not been adequately investigated. The present study aimed to explore the association between dietary inflammatory index (DII) and DKD in US adults.

DESIGN

This is a cross-sectional study.

SETTING

Data from the National Health and Nutrition Examination Survey (2007-2016) were used. DII was calculated from 24-h dietary recall interviews. DKD was defined as diabetes with albuminuria, impaired glomerular filtration rate or both. Logistic regression and restricted cubic spline models were adopted to evaluate the associations.

PARTICIPANTS

Data from the National Health and Nutrition Examination Survey (2007-2016) were used, which can provide the information of participants.

RESULTS

Four thousand two-hundred and sixty-four participants were included in this study. The adjusted OR of DKD was 1·04 (95 % CI 0·81, 1·36) for quartile 2, 1·24 (95 % CI 0·97, 1·59) for quartile 3 and 1·64 (95 % CI 1·24, 2·17) for quartile 4, respectively, compared with the quartile 1 of DII. A linear dose-response pattern was observed between DII and DKD (Pnonlinearity = 0·73). In the stratified analyses, the OR for quartile 4 of DII were significant among adults with higher educational level (OR 1·83, 95 % CI 1·26, 2·66) and overweight or obese participants (OR 1·67, 95 % CI 1·23, 2·28), but not among the corresponding another subgroup. The interaction effects between DII and stratified factors on DKD were not statistically significant (all P values for interactions were >0·05).

CONCLUSIONS

Our findings suggest that a pro-inflammatory diet, shown by a higher DII score, is associated with increased odd of DKD.

Diet Quality and Biological Risk in a National Sample of Older Americans

Objectives: Using comprehensive measures of biological risk, this study aims to investigate the relationship between intake of individual dietary components, overall diet quality, and biological dysregulation. Methods: We analyzed nationally representative data from 3734 older adults who participated in the Health and Retirement Study Venous Blood Study in 2016 and Health Care and Nutrition Survey in 2013. Results: Eleven out of 13 individual dietary components were associated with lower biological risk. Respondents with poor/suboptimal quality diet had higher biological risk than those with good quality diet. Discussion: Findings from this study emphasize the importance of healthy eating in improving health of older adults. Encouraging intake of fruits, greens and beans, whole grains, and fatty acids, while limiting consumption of sodium, added sugar, and saturated fat would improve overall diet quality and contribute to the prevention of chronic diseases and morbidity.

Associations of Physical Activity, Kidney Function, Diet, and Inflammatory Markers in High-Risk Type-2 Diabetes With Early-Stage Chronic Kidney Disease (CKD)

OBJECTIVES Quantitative information and associations of physical activity, kidney function, diet, and inflammation are dearth in high-risk diabetes. Yet could delay type-2 diabetes, late-stage chronic kidney disease (CKD) and could be useful in designing effective interventions. The study aims to quantify the associations of physical activity, kidney function, diet and inflammation in adults with high-risk type-2 diabetes (and early CKD) recruited to a lifestyle education programme.METHODS Baseline, 12-month dietary, accelerometery, and circulating inflammatory markers, Interleukin-6 (IL-6) and C-reactive protein (CRP) data were assessed from 159 (104 male) high-risk diabetes with stage 2 CKD (mean (SD) estimated glomerular filteration rate (eGFR); 77.5(7.6) ml/min/1.73m2, age; 66(6) years, BMI; 31.8(4.2) kg/m2) who were recruited to a lifestyle education programme. Linear regression examined the effects and associations of the outcome measures.RESULTS eGFR decreased by -2.0 (1.7) ml/min/1.73 m2 (P = 0.04) after 12-months, but mean daily steps, moderate to vigorous physical activity (MVPA) levels, intakes of fibre, total and unsaturated fat, and circulating IL-6 and CRP did not change. However, inter-individual responses were highly variable. eGFR correlated positively with baseline IL-6 (r = 0.17, P = 0.02). Unadjusted, there were no associations between change in eGFR (12_0) and change in any of the activity, inflammatory or dietary outcomes. However, the regression models of these outcomes for change in eGFR (12_0) became significant with multiple covariates.CONCLUSION A combination of healthy lifestyle behaviours should be encouraged for a positive effect on future kidney function.

Associations between Consumption of Dietary Fibers and the Risk of Type 2 Diabetes, Hypertension, Obesity, Cardiovascular Diseases, and Mortality in Chinese Adults: Longitudinal Analyses from the China Health and Nutrition Survey

Although many studies have explored the relationship between total dietary fiber intake and the risk of chronic non-communicable diseases, the results are mixed. There is also a lack of research on the association between dietary fiber intake from different food sources and disease. Using data from the China Nutrition and Health Database from 2004 to 2015, Cox proportional risk models were used to explore the associations between total dietary fiber and fiber intake from different food sources and the occurrence of type 2 diabetes, hypertension, obesity, cardiovascular disease, and all-cause mortality. After multi-factorial adjustment, the hazard ratios (95% confidence interval) of total dietary fiber intake (quartile 4 vs. quartile 1) in type 2 diabetes, hypertension, obesity, cardiovascular disease, and all-cause mortality cohorts were 1.20 (0.93, 1.55), 0.91 (0.75, 1.12), 0.93 (0.64, 1.35), 1.13 (0.60, 2.12), 1.13 (0.60, 2.12), and 1.13 (0.84, 1.52). Whole-grain fiber intake was positively associated with hypertension but not with the occurrence of other diseases. No association was observed between legume fibers, fruit fibers, and vegetable fibers in the cohorts of type 2 diabetes, hypertension, obesity, cardiovascular diseases and all-cause mortality. Our study did not find any association between total dietary fiber and dietary fiber intake from different food sources and type 2 diabetes, obesity, cardiovascular disease, and all-cause mortality in the Chinese population. The role of dietary fiber in the Chinese population may be overestimated. More extraordinary efforts are needed to further confirm the association between dietary fiber and these diseases in the Chinese population.

The association between dietary fiber intake and the concentrations of aldehydes in serum

Aldehydes have been shown to be potentially carcinogenic, mutagenic, and cardiotoxic to humans. Dietary fiber reduces exposure to certain environmental pollutants and has been widely used to improve various metabolic disorders. However, the effects of dietary fiber on serum concentrations of aldehydes remain unexplored. Data was collected from the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Generalized linear regression and restricted cubic spline models were performed to elucidate the association of dietary fiber intake with the serum concentration of aldehydes. After fully adjusting for age, sex, education level, race, smoking status, alcohol use, diabetes, hypertension, body mass index, energy intake, poverty-income ratio, and physical activity, dietary fiber intake had a strong negative association with serum levels of isopentanaldehyde and propanaldehyde and a positive association with serum levels of benzaldehyde. The estimated increases in the mean log2-unit (ng/mL) of aldehydes for each fold increase in dietary fiber were -0.140 (95% confidence interval [CI]: -0.195 to -0.085) for isopentanaldehyde, -0.060 (95% CI: -0.099 to -0.015) for propanaldehyde, and 0.084 (95% CI: 0.017 to 0.150) for benzaldehyde, respectively. No significant association was observed between dietary fiber intake and the concentration of any other aldehydes. These results demonstrate that dietary fiber reduces the concentration of certain aldehydes in serum.

Association between Dietary Fiber Intake and Hyperuricemia among Chinese Adults: Analysis of the China Adult Chronic Disease and Nutrition Surveillance (2015)

This study aimed to assess the association of dietary fiber intake with serum uric acid (SUA) levels and risk of hyperuricemia (HUA) among Chinese adults using the latest nationally representative data. A total of 66,427 Chinese adults aged 18 years and over from the China Adult Chronic Disease and Nutrition Surveillance in 2015 were included in this study. Dietary intakes were measured with a 3-day 24 h dietary recall and the household condiment weighing method. Mixed-effect linear and logistic regression models were used to evaluate the associations of dietary fiber intake with SUA levels and risk of HUA, respectively. Compared to the lowest intake group, the coefficient and 95% confidence in the highest intake group of total fiber were −0.06 (−0.08, −0.04) (p-trend < 0.001), −0.18 (−0.2, −0.16) (p-trend < 0.001) for cereal fiber, 0.03 (0.01, 0.04) (p-trend = 0.051) for legume fiber, 0 (−0.01, 0.02) (p-trend = 0.869) for vegetable fiber and 0.01 (−0.001, 0.04) (p-trend = 0.296) for fruit fiber. The odds ratio (OR) and 95% confidence interval (CI) of HUA for the highest vs. lowest intake group of total fiber were 0.88 (0.84, 0.91) (p-trend = 0.001), 0.67 (0.63, 0.71) (p-trend < 0.001) for cereal fiber, 1.05 (1, 1.09) (p-trend = 0.248) for legume fiber, 1.01 (0.97, 1.05) (p-trend = 0.982) for vegetable fiber and 1.06 (1, 1.12) (p-trend = 0.264) for fruit fiber. Our findings suggest that consumption of total fiber and cereal fiber were significantly inversely associated with SUA levels and HUA risk among the Chinese adult population. Developing and implementing effective public education programs are urgently needed to increase the intake of dietary fiber, especially cereal fiber among Chinese adults.

Differential Effect of Dietary Fibers in Intestinal Health of Growing Pigs: Outcomes in the Gut Microbiota and Immune-Related Indexes

Although dietary fibers (DFs) have been shown to improve intestinal health in pigs, it is unclear whether this improvement varies according to the type/source of DF. In the current study, we investigated the impact of dietary supplement (15%) of pea-hull fiber (PF), oat bran (OB), and their mixture (MIX, PF, and OB each accounted for 7.5%) in the growth performance as well as intestinal barrier and immunity-related indexes in growing pigs. Twenty-four cross-bred pigs (32.42 ± 1.95 kg) were divided into four groups: CON (basal diet with no additional DF), PF, OB, and MIX. After 56 days of feeding, we found that the growth performance of PF pigs was decreased (p < 0.05) compared with pigs in other groups. Results of real-time polymerase chain reaction and Western blot showed that the improvement of immune-related indexes (e.g., interleukin 10 [IL-10]) in OB and MIX pigs mainly presented in the ileum, whereas the improvement of intestinal barrier–related indexes (e.g., MUC1 and MUC2) mainly presented in the colon. Whether in the ileum or colon, such improvement of immune function may be dependent on NOD rather than TLR-associated pathways. Amplicon sequencing results showed that PF and MIX pigs shared a similar bacterial community, such as lower abundance of ileal Clostridiaceae and colonic Streptoccocus than that of CON pigs (p < 0.05). Our results indicate that OB and MIX, rather than PF, benefit the intestinal health in growing pigs, and multiple-sourced DF may reduce the adverse effect of single-soured DF on the growth performance and gut microbiota in pigs.

Fiber intake and health in people with chronic kidney disease

Emerging evidence suggests that diet, particularly one that is rich in dietary fiber, may prevent the progression of chronic kidney disease (CKD) and its associated complications in people with established CKD. This narrative review summarizes the current evidence and discusses the opportunities for increasing fiber intake in people with CKD to improve health and reduce disease complications. A higher consumption of fiber exerts multiple health benefits, such as increasing stool output, promoting the growth of beneficial microbiota, improving the gut barrier and decreasing inflammation, as well decreasing uremic toxin production. Despite this, the majority of people with CKD consume less than the recommended dietary fiber intake, which may be due in part to the competing dietary potassium concern. Based on existing evidence, we see benefits from adopting a higher intake of fiber-rich food, and recommend cooperation with the dietitian to ensure an adequate diet plan. We also identify knowledge gaps for future research and suggest means to improve patient adherence to a high-fiber diet.

Nutrition, Immunology, and Kidney: Looking Beyond the Horizons

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is epidemic throughout the word. Despite various novel therapeutic opportunities, CKD is still associated with high morbidity and mortality. In CKD, patient's chronic inflammation is frequent and related with adverse outcomes. Both innate and adaptive immunity are dysfunctional in CKD. Therefore, it is plausible to interfere with dysfunctional immunity in these patients. In the current review, we present the updated experimental and clinical data summarizing the effects of nutritional interventions including natural products and dietary supplements on immune dysfunction in the context of CKD.

RECENT FINDINGS

Nutritional interventions including natural products and dietary supplements (e.g., curcumin, sulforaphane, resistant starch, anthocyanin, chrysin, short chain fatty acids, fish oil resistant starch) slow down the inflammation by at least 6 mechanisms: (i) decrease nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB); (ii) decrease NLR family pyrin domain containing 3 (NLRP3); (iii) decrease interleukin-1 (IL-1), decrease interleukin-6 (IL-6) secretion; (iv) decrease polymorphonuclear priming); (v) promote anti-inflammatory pathways (nuclear factor-erythroid factor 2-related factor 2 (NFR2); (vi) increase T regulatory (Tregs) cells). Natural products and dietary supplements may provide benefit in terms of kidney health. By modulation of nutritional intake, progression of CKD may be delayed.

High Dietary Diabetes Risk Reduction Score Is Associated with Decreased Risk of Chronic Kidney Disease in Tehranian Adults

AIM

In the current study, we examined the association of dietary diabetes risk reduction score (DDRRS) with chronic kidney disease (CKD) among an Iranian adult population.

METHODS

We followed up 2076 ≥20-year-old participants of the Tehran Lipid and Glucose Study (2006-2008), who were initially free of CKD for 5.98 years. The dietary diabetes risk reduction score was calculated based on scoring eight components, including cereal fiber, nuts, coffee, polyunsaturated fatty acids-to-saturated fatty acids ratio, glycemic index, sugar-sweetened beverages, trans fatty acids, and red and processed meat using a valid and reliable 168-item food frequency questionnaire. CKD was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m². A Cox proportional hazard regression model was used to assess the association between the quartiles of DDRRS and CKD incidence.

RESULTS

Mean ± SD age of the study population (53% women) was 37.6 ± 12.61 years. During 5.98 years of follow-up, 357 incident cases of CKD were reported. The median (25-75 interquartile range) of DDRRS was 20 (18-22). After adjustment for age, sex, smoking status, total energy intake, body mass index, hypertension, diabetes, eGFR, and physical activity, individuals in the highest versus lowest quartile of DDRRS were 33% less likely to have CKD (HR: 0.67; 95% CI: 0.48-0.96, P for trend: 0.043).

CONCLUSION

The present study's findings suggest that greater adherence to a dietary pattern with a higher score of DDRRS may be associated with a lower risk of CKD incident.

Medical nutrition therapy using plant-focused low-protein meal plans for management of chronic kidney disease in diabetes

PURPOSE OF REVIEW

Nearly half of all Americans with chronic kidney disease (CKD) also have type-2-diabetes (T2D). Whereas traditional and emerging pharmacotherapies are increasingly frequently used for the management of CKD in diabetes (CKD/DM), the role of integrated or multimodal interventions including the potentially synergistic and additive effect of diet and lifestyle modifications in addition to pharmacotherapy has not been well examined, in sharp contrast to the well-known integrated approaches to heart disease.

RECENT FINDINGS

Low-carbohydrate low-fat diets are often recommended in T2D, whereas low-protein diets (LPD) are recommended by guidelines for nondiabetic CKD with increasing emphasis on plant-based protein sources. High-protein diets with greater animal protein lead to glomerular hyperfiltration, especially in patients with T2D, and faster decline in renal function. Guidelines provide differing recommendations regarding the amount (low vs high) and source (plant vs animal) of dietary protein intake (DPI) in CKD/DM. Some such as KDIGO recommend 0.8 g/kg/day based on insufficient evidence for DPI restriction in CKD/DM, whereas KDOQI and ISRNM recommend a DPI of 0.6 to <0.8 g/kg/day. A patient-centered plant-focused LPD for the nutritional management of CKD/DM (PLAFOND), a type of PLADO diet comprising DPI of 0.6 to <0.8 g/kg/day with >50% plant-based sources, high dietary fiber, low glycemic index, and 25-35 Cal/kg/day energy, can be implemented by renal dietitians under Medical Nutrition Therapy.

SUMMARY

Potential risks vs benefits of high vs low protein intake in CKD/DM is unknown, for which expert recommendations remain opinion based. Randomized controlled studies are needed to examine safety, acceptability and efficacy of PLAFOND.

Kidney disease risk factors do not explain impacts of low dietary protein on kidney function and structure

The kidneys balance many byproducts of the metabolism of dietary components. Previous studies examining dietary effects on kidney health are generally of short duration and manipulate a single macronutrient. Here, kidney function and structure were examined in C57BL/6J mice randomized to consume one of a spectrum of macronutrient combinations (protein [5%–60%], carbohydrate [20%–75%], and fat [20%–75%]) from weaning to late-middle age (15 months). Individual and interactive impacts of macronutrients on kidney health were modeled. Dietary protein had the greatest influence on kidney function, where chronic low protein intake decreased glomerular filtration rates and kidney mass, whereas it increased kidney immune infiltration and structural injury. Kidney outcomes did not align with cardiometabolic risk factors including glucose intolerance, overweight/obesity, dyslipidemia, and hypertension in mice with chronic low protein consumption. This study highlights that protein intake over a lifespan is an important determinant of kidney function independent of cardiometabolic changes.

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Chronic high macronutrient intake from any source increases kidney function (GFR)

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Low protein intake led to greater kidney tubular structural injury and inflammation

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Lower protein intake decreased kidney mass and glomerular filtration capacity

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Kidney outcomes did not align with longevity or cardiometabolic outcomes

Dietary strategies for gut-derived protein-bound uremic toxins and cardio-metabolic risk factors in chronic kidney disease: A focus on dietary fibers

Chronic kidney disease (CKD) is associated with altered composition and function of gut microbiota. The cause of gut dysbiosis in CKD is multifactorial and encompasses the following: uremic state, metabolic acidosis, slow colonic transit, dietary restrictions of plant-based fiber-rich foods, and pharmacological therapies. Dietary restriction of potassium-rich fruits and vegetables, which are common sources of fermentable dietary fibers, inhibits the conversion of dietary fibers to short-chain fatty acids (SCFA), which are the primary nutrient source for the symbiotic gut microbiota. Reduced consumption of fermentable dietary fibers limits the population of SCFA-forming bacteria and causes dysbiosis of gut microbiota. Gut dysbiosis induces colonic fermentation of protein and formation of gut-derived uremic toxins. In this review, we discuss the roles and benefits of dietary fiber on gut-derived protein-bound uremic toxins and plant-based dietary patterns that could be recommended to decrease uremic toxin formation in CKD patients. Recent studies have indicated that dietary fiber supplementation may be useful to decrease gut-derived uremic toxin formation and slow CKD progression. However, research on associations between adherence of healthy dietary patterns and gut-derived uremic toxins formation in patients with CKD is lacking.

How important is dietary management in chronic kidney disease progression? A role for low protein diets

High dietary protein intake may lead to increased intraglomerular pressure and glomerular hyperfiltration, which in the long-term can lead to de novo or aggravating preexisting chronic kidney disease (CKD). Hence, a low protein diet (LPD, 0.6 to 0.8 g/kg/day) is recommended for the management of CKD. There are evidences that dietary protein restriction mitigate progression of CKD and retard the initiation of dialysis or facilitate incremental dialysis. LPD is also helpful to control metabolic derangements in CKD such as metabolic acidosis and hyperphosphatemia. Recently, a growing body of evidence has emerged on the benefits of plant-dominant low-protein diet (PLADO), which composed of > 50% plant-based sources. PLADO is considered to be helpful for relieving uremic burden and metabolic complications in CKD compared to animal protein dominant consumption. It may also lead to favorable alterations in the gut microbiome, which can modulate uremic toxin generation along with reducing cardiovascular risk. Alleviation of constipation in PLADO may minimize the risk of hyperkalemia. A balanced and individualized dietary approach for good adherence to LPD utilizing various plant-based sources as patients' preference should be elaborated for the optimal care in CKD. Periodic nutritional assessment under supervision of trained dietitians should be warranted to avoid protein-energy wasting.

Dietary fiber and the microbiota: A narrative review by a group of experts from the Asociación Mexicana de Gastroenterología

Dietary fiber intake is one of the most influential and efficacious strategies for modulating the gut microbiota. Said fiber can be digested by the microbiota itself, producing numerous metabolites, which include the short-chain fatty acids (SCFAs). SCFAs have local and systemic functions that impact the composition and function of the gut microbiota, and consequently, human health. The aim of the present narrative review was to provide a document that serves as a frame of reference for a clear understanding of dietary fiber and its direct and indirect effects on health. The direct benefits of dietary fiber intake can be dependent on or independent of the gut microbiota. The use of dietary fiber by the gut microbiota involves several factors, including the fiber's physiochemical characteristics. Dietary fiber type influences the gut microbiota because not all bacterial species have the same capacity to produce the enzymes needed for its degradation. A low-fiber diet can affect the balance of the SCFAs produced. Dietary fiber indirectly benefits cardiometabolic health, digestive health, certain functional gastrointestinal disorders, and different diseases.

Dietary fiber and the microbiota: A narrative review by a group of experts from the Asociación Mexicana de Gastroenterología

Dietary fiber intake is one of the most influential and efficacious strategies for modulating the gut microbiota. Said fiber can be digested by the microbiota itself, producing numerous metabolites, which include the short-chain fatty acids (SCFAs). SCFAs have local and systemic functions that impact the composition and function of the gut microbiota, and consequently, human health. The aim of the present narrative review was to provide a document that serves as a frame of reference for a clear understanding of dietary fiber and its direct and indirect effects on health. The direct benefits of dietary fiber intake can be dependent on or independent of the gut microbiota. The use of dietary fiber by the gut microbiota involves several factors, including the fiber's physiochemical characteristics. Dietary fiber type influences the gut microbiota because not all bacterial species have the same capacity to produce the enzymes needed for its degradation. A low-fiber diet can affect the balance of the SCFAs produced. Dietary fiber indirectly benefits cardiometabolic health, digestive health, certain functional gastrointestinal disorders, and different diseases.

Dietary Amino Acid Patterns Are Associated With Incidence of Chronic Kidney Disease

OBJECTIVES

No findings are available regarding the association of the dietary amino acid (AA) intakes with the risk of chronic kidney disease (CKD) in adults. We aimed to assess the association between dietary AA patterns and incidence of CKD in adults.

DESIGN AND METHODS

This study was conducted within the framework of Tehran Lipid and Glucose Study on 4,233 adults, who were free of CKD at baseline (2009-2011) and were followed for 3.1 years (2011-2014). The principal component analysis was used based on 8 AA groups to characterize major AA patterns. Multivariable logistic regression models were used to estimate the risk of CKD across quartiles of dietary AA pattern scores.

RESULTS

Three major AA patterns were extracted: (1) higher loads of branched-chain, alcoholic, and aromatic AAs; (2) higher loads of acidic AAs, proline, and lower load of alkaline AAs and small AAs; and (3) higher loads of sulfuric AAs and small AAs. The mean ± standard deviation age of participants (45.9% male) was 39.4 ± 11.7 at baseline and the incidence of CKD was 12.1% (513 cases) after 3.1 years of follow-up. The highest score of first dietary AA pattern tended to be associated with an increased risk of CKD (odds ratio = 1.43, 95% confidence interval1.06-1.93); however, the second pattern was related to a decreased risk of CKD (odds ratio = 0.71, 95% confidence interval: 0.52-0.97) in the multivariable model.

CONCLUSION

These novel findings suggest that the dietary AA patterns may modify risk of CKD.

Microbiome modulation as a novel therapeutic approach in chronic kidney disease

PURPOSE OF REVIEW

Gut dysbiosis has been implicated in the pathogenesis of chronic kidney disease (CKD). Interventions aimed at restoring gut microbiota have emerged as a potential therapeutic option in CKD. This review summarizes the current evidence on gut microbiota-targeted strategies in patients with CKD.

RECENT FINDINGS

A growing number of studies have shown that plant-based diets, low-protein diets, prebiotic, probiotic, and synbiotic supplementation, and constipation treatment may lead to favorable alterations in the gut microbiota. Current evidence suggests that the implementation of both plant-based and low-protein diets has potential benefits for the primary prevention of CKD, and for slowing CKD progression, with minimal risk of hyperkalemia and/or cachexia. The use of prebiotics, probiotics, and synbiotics and laxatives may have beneficial effects on uremic toxin generation, but their evidence is limited for the prevention and treatment of CKD. Recent advances in diagnostic technologies (e.g., high-throughput sequencing and nanotechnology) could enhance rapid diagnosis, monitoring, and design of effective therapeutic strategies for mitigating gut dysbiosis in CKD.

SUMMARY

Plant-based and low-protein diets, prebiotic, probiotic, and synbiotic supplementation, and constipation treatment represent novel gut microbiota-targeted strategies in the conservative management of CKD, which could improve clinical outcomes in CKD.

Source and Composition in Amino Acid of Dietary Proteins in the Primary Prevention and Treatment of CKD

Nutrition is a cornerstone in the management of chronic kidney disease (CKD). To limit urea generation and accumulation, a global reduction in protein intake is routinely proposed. However, recent evidence has accumulated on the benefits of plant-based diets and plant-derived proteins without a clear understanding of underlying mechanisms. Particularly the roles of some amino acids (AAs) appear to be either deleterious or beneficial on the progression of CKD and its complications. This review outlines recent data on the role of a low protein intake, the plant nature of proteins, and some specific AAs actions on kidney function and metabolic disorders. We will focus on renal hemodynamics, intestinal microbiota, and the production of uremic toxins. Overall, these mechanistic effects are still poorly understood but deserve special attention to understand why low-protein diets provide clinical benefits and to find potential new therapeutic targets in CKD.

Mediterranean diet and the risk of chronic kidney disease: A systematic review and meta-analysis

OBJECTIVE

Mediterranean diet has been shown to be associated with lower risk of cardiovascular disease. However, its association with chronic kidney disease (CKD) remains inconclusive as the results were not consistent among population-based studies. This study aims to assess the association between Mediterranean diet adherence and CKD prevention.

METHODS

We performed a systematic review and meta-analysis of studies describing the risk for CKD in community-dwelling subjects ≥18 years of age. Mediterranean diet adherence was assessed by standardized food frequency questionnaires. The search was conducted through MEDLINE, EMBASE and Cochrane Library.

RESULTS

Of 168 citations, a total of nine (n = 19 151) and four studies (n = 8467) were included in the systematic review and meta-analysis, respectively. Only studies adopting Mediterranean Diet Scale (MDS) were included in the analysis. The mean score was 3.8 ± 0.3 points. With the mean follow-up duration of 20.6 ± 7.0 years, the pooled odds ratio (OR) for CKD was 0.901 (95% confidence interval [CI] 0.868-0.935) for each 1-point increment of MDS. The incidence of CKD was 0.026 events per person-year (95% CI 0.008-0.045). Moreover, male sex was associated with the incidence of CKD in an adjusted meta-regression analysis. In contrast, there was no significant association between age, black race, smoking, diabetes, hypertension estimated glomerular filtration rate and total daily energy intake vs CKD incidence.

CONCLUSION

Adherence to Mediterranean diet by a 1-point increment of MDS was associated with 10% lower risk of CKD. However, there were insufficient data on patients with pre-existing CKD or dialysis.

Healthy adult vegetarians have better renal function than matched omnivores: a cross-sectional study in China

Background

An appropriate diet is an important determinant of kidney health. However, the association between vegetarian diets and renal function is unclear. We aimed to study the association between vegetarian diets and renal function in healthy adults.

Methods

A total of 269 vegetarians and 269 sex- and age-matched nonvegetarian omnivores were enrolled in this cross-sectional study. Basic characteristics and daily dietary intakes were assessed by face-to-face interviews. Blood samples were collected, and renal function was assessed by measuring blood urea nitrogen (BUN), serum creatinine (SCr), uric acid (UA) and the estimated glomerular filtration rate (eGFR). Blood pressure, fasting blood glucose and blood lipid profiles were also assessed.

Results

The average age of the vegetarians was 35.4 ± 8.6 years, 82.2% of whom were female. We evaluated the association between vegetarian diets and renal function using multivariate analysis. Compared with omnivores, vegetarians had lower BUN [β = − 0.63, 95% confidence interval (CI): (− 0.88, − 0.38)], SCr [β = − 2.04, 95% CI:(− 4.10, 0.02)], and UA levels [β = − 15.15, 95% CI: (− 27.81, − 2.50)] and higher eGFRs [β = 4.04, 95% CI: (0.30, 7.78)] after adjusting for sex, age, body mass index (BMI), physical activity, alcohol consumption, smoking status, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), systolic pressure and fasting blood glucose. Further analysis of food composition and renal function showed that dietary fiber intake was significantly negatively associated with BUN [β = − 0.02, 95% CI: (− 0.03, 0.00)], SCr [β = − 0.14, 95% CI: (− 0.25, 0.04)], and UA levels [β = − 0.72, 95% CI: (− 1.36, 0.07)] and positively associated with the eGFR [β = 0.20, 95% CI: (0.00, 0.40)].

Conclusions

Healthy adult vegetarians have better renal function than omnivores, and the higher dietary fiber intake associated with vegetarian diets may contribute to the protective effect on renal function.

Plant-Dominant Low-Protein Diet for Conservative Management of Chronic Kidney Disease

Chronic kidney disease (CKD) affects >10% of the adult population. Each year, approximately 120,000 Americans develop end-stage kidney disease and initiate dialysis, which is costly and associated with functional impairments, worse health-related quality of life, and high early-mortality rates, exceeding 20% in the first year. Recent declarations by the World Kidney Day and the U.S. Government Executive Order seek to implement strategies that reduce the burden of kidney failure by slowing CKD progression and controlling uremia without dialysis. Pragmatic dietary interventions may have a role in improving CKD outcomes and preventing or delaying dialysis initiation. Evidence suggests that a patient-centered plant-dominant low-protein diet (PLADO) of 0.6–0.8 g/kg/day composed of >50% plant-based sources, administered by dietitians trained in non-dialysis CKD care, is promising and consistent with the precision nutrition. The scientific premise of the PLADO stems from the observations that high protein diets with high meat intake not only result in higher cardiovascular disease risk but also higher CKD incidence and faster CKD progression due to increased intraglomerular pressure and glomerular hyperfiltration. Meat intake increases production of nitrogenous end-products, worsens uremia, and may increase the risk of constipation with resulting hyperkalemia from the typical low fiber intake. A plant-dominant, fiber-rich, low-protein diet may lead to favorable alterations in the gut microbiome, which can modulate uremic toxin generation and slow CKD progression, along with reducing cardiovascular risk. PLADO is a heart-healthy, safe, flexible, and feasible diet that could be the centerpiece of a conservative and preservative CKD-management strategy that challenges the prevailing dialysis-centered paradigm.

Plant-based diets to manage the risks and complications of chronic kidney disease

Traditional dietary recommendations for patients with chronic kidney disease (CKD) focus on the quantity of nutrients consumed. Without appropriate dietary counselling, these restrictions can result in a low intake of fruits and vegetables and a lack of diversity in the diet. Plant nutrients and plant-based diets could have beneficial effects in patients with CKD: increased fibre intake shifts the gut microbiota towards reduced production of uraemic toxins; plant fats, particularly olive oil, have anti-atherogenic effects; plant anions might mitigate metabolic acidosis and slow CKD progression; and as plant phosphorus has a lower bioavailability than animal phosphorus, plant-based diets might enable better control of hyperphosphataemia. Current evidence suggests that promoting the adoption of plant-based diets has few risks but potential benefits for the primary prevention of CKD, as well as for delaying progression in patients with CKD G3-5. These diets might also help to manage and prevent some of the symptoms and metabolic complications of CKD. We suggest that restriction of plant foods as a strategy to prevent hyperkalaemia or undernutrition should be individualized to avoid depriving patients with CKD of these potential beneficial effects of plant-based diets. However, research is needed to address knowledge gaps, particularly regarding the relevance and extent of diet-induced hyperkalaemia in patients undergoing dialysis.

Plant-based diets, insulin sensitivity and inflammation in elderly men with chronic kidney disease

BACKGROUND

In persons with CKD, adherence to plant-based diets is associated with lower risk of CKD progression and death, but underlying mechanisms are poorly characterized. We here explore associations between adherence to plant-based diets and measures of insulin sensitivity and inflammation in men with CKD stages 3-5.

METHODS

Cross-sectional study including 418 men free from diabetes, aged 70-71 years and with cystatin-C estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m² and not receiving kidney-specific dietetic advice. Information from 7-day food records was used to evaluate the adherence to a plant-based diet index (PBDi), which scores positively the intake of plant-foods and negatively animal-foods. Insulin sensitivity and glucose disposal rate were assessed with the gold-standard hyperinsulinemic euglycemic glucose clamp technique. Inflammation was evaluated by serum concentrations of C-reactive protein (CRP) and interleukin (IL)-6. Associations were explored through linear regression and restricted cubic splines.

RESULTS

The majority of men had CKD stage 3a. Hypertension and cardiovascular disease were the most common comorbidities. The median PBDi was 38 (range 14-55). Across higher quintiles of PBDi (i.e. higher adherence), participants were less often smokers, consumed less alcohol, had lower BMI and higher eGFR (P for trend <0.05 for all). Across higher PBDi quintiles, patients exhibited higher insulin sensitivity and lower inflammation (P for trend <0.05). After adjustment for eGFR, lifestyle factors, BMI, comorbidities and energy intake, a higher PBDi score remained associated with higher glucose disposal rate and insulin sensitivity as well as with lower levels of IL-6 and CRP.

CONCLUSION

In elderly men with non-dialysis CKD stages 3-5, adherence to a plant-based diet was associated with higher insulin sensitivity and lower inflammation, supporting a possible role of plant-based diets in the prevention of metabolic complications of CKD.

Chronic inflammation in end-stage renal disease and dialysis

Under normal conditions, inflammation is a protective and physiological response to various harmful stimuli. However, in several chronic debilitating disorders, such as chronic kidney disease, inflammation becomes maladaptive, uncontrolled and persistent. Systemic persistent inflammation has, for almost 20 years, been recognized as a major contributor to the uraemic phenotype (such as cardiovascular disease, protein energy wasting, depression, osteoporosis and frailty), and a predictor of cardiovascular and total mortality. Since inflammation is mechanistically related to several ageing processes (inflammageing), it may be a major driver of a progeric phenotype in the uraemic milieu. Inflammation is likely the consequence of a multifactorial aetiology and interacts with a number of factors that emerge when uraemic toxins accumulate. Beside interventions aiming to decrease the production of inflammatory molecules in the uraemic milieu, novel strategies to increase the removal of large middle molecules, such as expanded haemodialysis, may be an opportunity to decrease the inflammatory allostatic load associated with retention of middle molecular weight uraemic toxins.

Dietary Fiber and Gut Microbiota in Renal Diets

Nutrition is crucial for the management of patients affected by chronic kidney disease (CKD) to slow down disease progression and to correct symptoms. The mainstay of the nutritional approach to renal patients is protein restriction coupled with adequate energy supply to prevent malnutrition. However, other aspects of renal diets, including fiber content, can be beneficial. This paper summarizes the latest literature on the role of different types of dietary fiber in CKD, with special attention to gut microbiota and the potential protective role of renal diets. Fibers have been identified based on aqueous solubility, but other features, such as viscosity, fermentability, and bulking effect in the colon should be considered. A proper amount of fiber should be recommended not only in the general population but also in CKD patients, to achieve an adequate composition and metabolism of gut microbiota and to reduce the risks connected with obesity, diabetes, and dyslipidemia.

Greater Dietary Inflammatory Index score is associated with higher likelihood of chronic kidney disease

Chronic kidney disease (CKD) is described as a progressive alteration of kidney function, resulting from multiple factors, including behaviours. We investigated the association of the Dietary Inflammatory Index (DII®) with prevalent CKD in adult Americans. National Health and Nutrition Examination Survey participants with measured data on kidney function markers from 2005 to 2012 were included in this study. Prevalent CKD was based on an estimated glomerular filtration rate (eGFR) <60 ml/min per 1·73 m2 or urinary albumin/creatinine≥30 mg/g. Energy-adjusted DII (E-DIITM) scores were calculated from 24-h dietary recalls. Statistical analyses accounted for the survey design and sample weights. We included 21 649 participants, with 1634 (6·8 %) having prevalent CKD. Participants with high E-DII scores had greater BMI, fasting blood glucose and systolic blood pressure, and were more likely to be diabetic or hypertensive (all P<0·001) compared with those with lower E-DII scores. In regression models adjusted for age, sex, race, fasting blood glucose, blood pressure, BMI, hypertension and diabetes status, mean eGFR significantly decreased across increasing quartiles of E-DII, whereas serum uric acid level and log urinary albumin:creatinine ratio significantly increased (all P<0·001). Prevalent CKD increased from 5·3 % in the lowest to 9·3 % in the highest E-DII quartile (P=0·02). In multivariable-adjusted logistic regression models, the odds of prevalent CKD were 29 % higher in the highest compared with the lowest E-DII quartile. Pro-inflammatory diet is associated with declining kidney function and high prevalence of CKD. Dietary changes that reduce inflammation have a potential to prevent CKD.