Protein Intake and Long-term Change in Glomerular Filtration Rate in the Jackson Heart Study

Relationship of Different Sourced Protein Intake, Quantity of Plasma Amino Acid with Chronic Kidney Disease

BACKGROUND

The association of protein from different food sources and different plasma amino acids with risk of chronic kidney disease (CKD) is unclear.

OBJECTIVES

We aimed to investigate longitudinal relationships of dietary protein intake from different sources and quantity of plasma amino acids with new-onset CKD in the general population.

METHODS

Participants (mean age: 56 y) without CKD at baseline were included in the UK Biobank. A total of 176,980 were included in the analysis for protein intakes and 99,061 participants were included in the analysis for plasma amino acids. Information on dietary protein was collected based on a 24-h dietary recall from the previous day. Plasma amino acid concentrations were measured by a high-throughput nuclear magnetic resonance (NMR)-based metabolic biomarker profiling platform. The study outcome was new-onset CKD.

RESULTS

During a median follow-up of 12 y (beginning between 2006 and 2010 and ending in 2021), 3542 participants (2,128,626 person-year) developed new-onset CKD. Higher intakes of dairy-derived and fish-derived protein were associated with lower incidence of CKD [per standard deviation, SD increment, adjusted hazard ratio, HR (95% confidence interval, 95% CI): 0.95 (0.91, 0.98) and 0.95 (0.92, 0.99), respectively], but protein intake from other foods was not (P-trend > 0.1). Moreover, incident CKD was lower among those with higher plasma histidine (per SD increment; adjusted HR = 0.90; 95% CI: 0.86, 0.95), tyrosine (0.90; 0.87, 0.94), isoleucine (0.89; 0.85, 0.92), leucine (0.89; 0.85, 0.93), and valine (0.89; 0.85, 0.93).

CONCLUSIONS

The protein intake from dairy and fish, as well as the concentration of plasma histidine, tyrosine, isoleucine, leucine, and valine, was inversely associated with new-onset CKD.

The Effect of Protein Intake on Bone Disease, Kidney Disease, and Sarcopenia: A Systematic Review

Background

Protein is essential for optimal growth, function, and maintenance of health. Its impact on bone, kidney health, and sarcopenia progression remains debated.

Objectives

This review examines the association between dietary protein intake and the risk of bone disease, kidney disease, and sarcopenia to inform protein dietary reference intake updates.

Methods

We searched Medline, EMBASE, AGRICOLA, and Scopus from January 2000 to May 2024, supplemented by citation searching for relevant reviews and original research. We included randomized and nonrandomized controlled trials, prospective cohort studies, and nested case-control studies examining dietary protein intake without exercise. We assessed the risk of bias (RoB), performed a qualitative synthesis of low to moderate RoB studies, and evaluated the strength of evidence.

Results

Of 82 articles detailing 81 unique studies, only 13 were assessed with low to moderate RoB and synthesized, comprising bone disease [4 randomized controlled trials (RCTs) and 1 prospective cohort study], kidney disease (1 RCT), and sarcopenia (9 RCTs). The overarching evidence was insufficient, largely due to the limited number of low to moderate RoB studies, the diversity of dietary protein interventions, and the broad range of outcomes, which complicated synthesis and comparison. Notably, sparse literature addressed children and adolescents, and only a single study each examined the impact of dietary protein intake on bone disease risk (yielding mixed findings) in these populations and on kidney disease risk (showing no significant effects) in adults. The findings on the impact of protein intake on bone disease in adults and sarcopenia risk were mixed; some studies showed no effect, whereas others indicated benefits.

Conclusions

The evidence since 2000 on associations between dietary protein intake and the risks of bone disease, kidney disease, and sarcopenia is unclear, indicating a need for more rigorous research.This trial was registered at PROSPERO as CRD42023446621.

Isomaltodextrin inhibits kidney enlargement induced by a high-protein diet through its metabolism by gut microbiota

To evaluate the effects of the soluble fiber isomaltodextrin in a protein-biased diet, a 21-day protein diet trial was conducted in rats, with 60% of the calories derived from protein. The results revealed that the high-protein diet alone led to a significant increase in kidney weight. In contrast, the consumption of water with 5% isomaltodextrin dissolved in it, along with a high-protein diet, suppressed this weight gain. To elucidate this mechanism, an analysis of serum urea toxins confirmed that the concentrations of phenyl sulfate were significantly higher with high protein, and significantly lower with isomaltodextrin. The impact of a high-protein diet increased phenol in cecal contents, an increase that was mitigated by isomaltodextrin. This suggests that the inhibitory effect of isomaltodextrin on renal hypertrophy was due to the suppression of urea toxin precursor production by the gut microbiota.

Diabetes and Glucose Management in People on Hemodialysis

Diabetes is a major cause of end-stage kidney disease (ESKD). Glycemic management is challenging in this population, and A1C, commonly used for monitoring glycemic control, is unreliable. Continuous glucose monitoring indices can be used for glycemic monitoring in people with ESKD. Dipeptidyl peptidase 4 inhibitors, incretin mimetic agents (glucagon-like peptide 1 and glucose-dependent insulinotropic peptide receptor agonists), and insulin using an automated insulin delivery system are preferred to manage diabetes in people with ESKD on hemodialysis.

The Effect of Dietary Fiber on Hyperkalemia in Maintenance Hemodialysis Patients: A Cross-Sectional Study

OBJECTIVE

To explore the relationship between dietary fiber (DF) intake and hyperkalemia in maintenance hemodialysis (MHD) patients.

METHODS

A total of 110 MHD patients were included, including 67 males and 43 females. Patients were divided into normal serum potassium group (N) and a hyperkalemia group (H) according to the serum potassium level before dialysis. The daily diet was recorded by the 3-day dietary recording method. The daily dietary nutrient intake of patients was analyzed. Logistic regression was used to analyze the relationship between hyperkalemia and DF intake. A receiver operating characteristic curve was used to analyze the cutoff value of DF intake to prevent hyperkalemia.

RESULTS

Of the 110 patients, 38 had hyperkalemia (serum potassium >5.5 mmol/L) before dialysis. There was no difference in sex, residual kidney function, body mass index, energy intake, fat intake, protein intake, calcium intake, sodium intake, phosphorus intake or the administration history of potassium-lowering drugs between the 2 groups (P > .05). Compared with the H group, patients in the N group had higher carbohydrate intake (315 ± 76 g/d vs. 279 ± 66 g/d, P = .016), dietary fiber intake (19 ± 5 g/d vs. 12 ± 8 g/d, P < .0001), and potassium intake (1,698 ± 392 mg/d vs. 1,533 ± 413 mg/d, P = .041), and more patients in group N used renin-angiotensin-aldosterone system inhibitors (52.78% vs. 23.68%, P = .003). However, the number of patients with constipation in group N was less than that in group H (20.83% vs. 42.11%, P = .018). Logistic regression analysis showed that DF intake was an independent protective factor for hyperkalemia [P < .0001, odds ratio = 0.766 (95% confidence intervals: 0.675-0.870)]. Receiver operating characteristic analysis showed that daily intake of DF greater than 15.33 g may be helpful to prevent hyperkalemia.

CONCLUSION

Insufficient dietary nutrient intake is prevalent in MHD patients, especially DF intake, which may be associated with hyperkalemia. Clinically, attention should be given to the dietary balance of MHD patients, especially DF intake.

Association of plant and animal protein intake with sleep quality and quality of life in hemodialysis patients: a multicenter cross-sectional study

Background

The current study aimed to evaluate the association between the intake of plant-based protein, animal-based protein, total protein, and the ratio of plant to animal protein with sleep quality and quality of life in patients undergoing hemodialysis.

Methods

In this cross-sectional study, 479 adult patients undergoing dialysis for a minimum of 3 months were included. The dietary intake was calculated using information from a validated 168-item semi-quantitative food frequency questionnaire. Quality of life (QOL) was assessed using the Kidney Disease Quality of Life Short Form (KDQOL-SF 1.3). and the Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality.

Results

In this study, the mean age of the participants was 58.18 years (± 14.25 years), with the majority being male (58.2%). After adjusting for potential confounders, significant positive associations were observed between total protein intake (β = 0.12, p = 0.03) and quality of life (QOL). Conversely, there were significant negative associations between the ratio of plant to animal protein intake (β = -0.94, p < 0.01) and QOL. Furthermore, significant negative associations were found between total protein intake (β = -0.02, p < 0.05) and animal protein intake (β = -0.19, p < 0.05) with poor sleep quality. Additionally, there were significant positive associations between the ratio of plant to animal protein intake (β = 0.188, p < 0.05) and poor sleep quality.

Conclusion

Increased consumption of animal protein is associated with improved sleep quality and Quality of Life (QOL) in patients undergoing hemodialysis (HD). Further research, especially prospective studies, is required to confirm these associations.

High Protein Diets and Glomerular Hyperfiltration in Athletes and Bodybuilders: Is Chronic Kidney Disease the Real Finish Line?

Several observational and experimental studies in humans have suggested that high protein intake (PI) causes intraglomerular hypertension leading to hyperfiltration. This phenomenon results in progressive loss of renal function with long-term exposure to high-protein diets (HPDs), even in healthy people. The recommended daily allowance for PI is 0.83 g/kg per day, which meets the protein requirement for approximately 98% of the population. A HPD is defined as a protein consumption > 1.5 g/kg per day. Athletes and bodybuilders are encouraged to follow HPDs to optimize muscle protein balance, increase lean body mass, and enhance performance. A series of studies in resistance-trained athletes looking at HPD has been published concluding that there are no harmful effects of HPD on renal health. However, the aim of these studies was to evaluate body composition changes and they were not designed to assess safety or kidney outcomes. Here we review the effects of HPD on kidney health in athletes and healthy individuals with normal kidney function.

Addition of bioimpedance-derived body cell mass improves performance of serum creatinine-based GFR estimation in a chronic kidney disease cohort

PURPOSE

Serum creatinine-based glomerular filtration rate (GFR) estimating equations are imprecise and systemic overestimate GFR in chronic kidney disease (CKD) populations with low muscle mass. Bioimpedance devices can measure body cell mass (BCM), a surrogate for muscle mass which has been included in a published GFR estimating equation. This BCM GFR equation is validated and compared with MDRD and CKD-EPI 2021 equations in an Indian CKD population.

METHODS

Patients with stable CKD stages 1-5 and voluntary kidney donors underwent measurement of serum creatinine, DTPA GFR and bioimpedance on the same day. BCM GFR was tested for consistency, agreement and performance with respect to DTPA GFR.

RESULTS

A total of 125 study participants were enrolled, including 106 patients with CKD (Stage 1: 8; stage 2: 32, stage 3: 42, stage 4: 20 and stage 5: 4 patients) and 19 voluntary kidney donors, with 66% males, and a mean age of 43.3 (± 16.5) years. The median bias of BCM GFR was 5.45 ml/min/1.73 m2 [95% confidence interval (CI) 4.2-8.3], absolute precision was 10.16 ml/min/1.73 m2 [95% CI 4.5-12.6], P30 was 59.1% [95% CI 50.0-67.7] and accuracy was 8.62% [95% CI 6.4-20.0]. Kappa measurement of agreement was the highest for BCM GFR-based staging (0.628 vs 0.545 for MDRD and 0.487 for CKD-EPI).

CONCLUSION

BCM-based GFR estimating equation performed better than MDRD and CKD-EPI equations in this Indian CKD population, and BCM GFR-based KDIGO staging was associated with lesser misclassification than the MDRD and CKD-EPI equations.

TRIAL REGISTRATION (PROSPECTIVE)

Clinical Trials Registry of India (CTRI/2019/11/021850).

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.

The association between plant and animal protein intake and quality of life in patients undergoing hemodialysis

Background

Hemodialysis (HD) patients often experience a significant reduction in quality of life (QOL). The source of dietary protein intake may influence the renal function and complications of HD patients. The present study assessed the relationship between plant and animal protein intake and QOL in HD patients.

Methods

264 adult patients under dialysis for at least three months were included in this cross-sectional study. Dietary intakes were collected using a valid and reliable 168-item semi-quantitative food frequency questionnaire (FFQ) over the past year. Total, animal, and plant proteins were calculated for each patient. To evaluate QOL, Kidney Disease Quality of Life Short Form (KDQOL-SF 1/3) was used. Anthropometric measures were assessed according to standard protocols.

Results

In this study, the average age of participants was 58.62 ± 15.26 years old; most (73.5%) were men. The mean of total, plant, and animal proteins intake were 66.40 ± 34.29 g/d, 34.60 ± 18.24 g/d, and 31.80 ± 22.21 g/d. Furthermore, the mean score of QOL was 59.29 ± 18.68. After adjustment for potential confounders, a significant positive association was found between total dietary protein intake and QOL (β = 0.12; p = 0.03). Moreover, there was a significant association between plant-based protein intake and QOL (β = 0.26; p < 0.001). However, the association between animal protein intake and QOL was insignificant (β = 0.03; p = 0.60).

Conclusion

Higher total and plant proteins intake were associated with better QOL in HD patients. Further studies, particularly prospective ones, are needed to corroborate these associations.

Dietary Protein, Chronic Salt-Sensitive Hypertension, and Kidney Damage

It has been estimated that over a fifth of deaths worldwide can be attributed to dietary risk factors. A particularly serious condition is salt-sensitive (SS) hypertension and renal damage, participants of which demonstrate increased morbidity and mortality. Notably, a large amount of evidence from humans and animals has demonstrated that other components of the diet can also modulate hypertension and associated end-organ damage. Evidence presented in this review provides support for the view that immunity and inflammation serve to amplify the development of SS hypertension and leads to malignant disease accompanied by tissue damage. Interestingly, SS hypertension is modulated by changes in dietary protein intake, which also influences immune mechanisms. Together, the evidence presented in this review from animal and human studies indicates that changes in dietary protein source have profound effects on the gut microbiota, microbiota-derived metabolites, gene expression, immune cell activation, the production of cytokines and other factors, and the development of SS hypertension and kidney damage.

Plant-Dominant Low Protein Diet: A Potential Alternative Dietary Practice for Patients with Chronic Kidney Disease

Dietary protein restriction has long been a cornerstone of nutritional therapy for patients with chronic kidney diseases (CKD). However, the recommended amount of dietary protein intake is different across guidelines. This is partly because previous randomized controlled trials have reported conflicting results regarding the efficacy of protein restriction in terms of kidney outcomes. Interestingly, a vegetarian, very low protein diet has been shown to reduce the risk of kidney failure among patients with advanced CKD, without increasing the incidence of hyperkalemia. This finding suggests that the source of protein may also influence the kidney outcomes. Furthermore, a plant-dominant low-protein diet (PLADO) has recently been proposed as an alternative dietary therapy for patients with CKD. There are several potential mechanisms by which plant-based diets would benefit patients with CKD. For example, plant-based diets may reduce the production of gut-derived uremic toxins by increasing the intake of fiber, and are useful for correcting metabolic acidosis and hyperphosphatemia. Plant proteins are less likely to induce glomerular hyperfiltration than animal proteins. Furthermore, plant-based diets increase magnesium intake, which may prevent vascular calcification. More evidence is needed to establish the efficacy, safety, and feasibility of PLADO as a new adjunct therapy in real-world patients with CKD.

Association of dietary proteins with serum creatinine and estimated glomerular filtration rate in a general population sample: the CHRIS study

BACKGROUND

Diet is known to affect kidney function. However, population-based studies provide contrasting evidence, resulting in a poor understanding of the effect of proteins from specific foods on kidney health.

METHODS

We analyzed the effect of total daily protein intake (TDPI) and source-specific daily protein intake (DPI) on fasting serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) in the Cooperative Health Research In South Tyrol (CHRIS) cross-sectional study (n = 5889), using the GA²LEN food frequency questionnaire for TDPI and DPI estimation. We fitted multivariable adjusted mixed models of SCr and eGFR on TDPI and DPI quartiles (Q1-Q4) in the overall sample, and after removing individuals with known hypertension, diabetes or chronic kidney disease (CKD).

RESULTS

Higher TDPI as well as DPI from overall animal sources, fish, and poultry, were associated with higher SCr (trend test p, p_trend < 0.01), with larger effect after excluding individuals with known hypertension, diabetes or CKD. The eGFR was lower at higher TDPI (Q4 vs Q1: - 1.6 ml/min/1.73 m²; 95% CI - 2.5, - 0.7; p_trend = 3e-4) and DPI from fish (Q4 vs Q1: - 2.1 ml/min/1.73 m²; 95% CI - 2.9, - 1.20; p_trend = 4.3e-6), overall animal source (Q4 vs Q1: - 1.6 ml/min/1.73 m²; 95% CI -2.5, - 0.8), processed meat (Q4 vs Q1: - 1.4 ml/min/1.73 m²; p_trend = 0.027), red meat, offal and processed meat (Q4 vs Q1: - 1.4 ml/min/1.73 m²; p_trend = 0.015) and poultry (Q4 vs Q1: - 0.9 ml/min/1.73 m²; p_trend = 0.015).

CONCLUSIONS

TDPI and DPI from specific animal sources were positively associated with SCr and negatively associated with eGFR. Lacking an alternative marker of kidney function, confounding involving muscle mass metabolism cannot be fully excluded.

Gut-Immune-Kidney Axis: Influence of Dietary Protein in Salt-Sensitive Hypertension

Humans with salt-sensitive hypertension demonstrate increased morbidity, increased mortality, and renal end-organ damage when compared with normotensive subjects or those with salt-resistant hypertension. Substantial evidence from humans and animals has also demonstrated the role of dietary components other than salt to modulate hypertension. Evidence presented in this review provides support for the view that immunity and inflammation serve to amplify the development of salt-sensitive hypertension and leads to malignant disease accompanied by end-organ damage. Interestingly, salt-sensitive disease is modulated by changes in dietary protein intake, which also influences immune mechanisms. Together, the evidence presented in this review from animal and human studies indicates that changes in dietary protein source have profound effects on the gut microbiota, microbiota-derived metabolites, DNA methylation, gene expression, immune cell activation, the production of cytokines and other factors, and the development of salt-sensitive hypertension and related disease phenotypes.

Low-protein diet is inversely related to the incidence of chronic kidney disease in middle-aged and older adults: results from a community-based prospective cohort study

PURPOSE

Dietary protein intake can modulate renal health. However, the effect of dietary protein restriction on kidney function in the general population remains unclear. This study aimed to examine the association between total protein intake and new-onset chronic kidney disease (CKD) in Korean adults.

METHODS

We included 7339 participants from the Korean Genome and Epidemiology Study. Participants were divided into low-protein diet (LPD, < 0.8 g/kg/day), normal-protein diet (NPD, 0.8-1.3 g/kg/day), and high-protein diet (HPD, > 1.3 g/kg/day) groups. New-onset CKD was defined as two consecutive events of estimated glomerular filtration rate < 60 mL/min/1.73 m². Multivariable Cox hazard regression analysis was conducted to examine the association of total protein intake with new-onset CKD. Subgroup analyses according to diabetes mellitus (DM) status were performed. We performed the same analyses by dividing participants into total protein, plant protein, and animal protein intake tertiles.

RESULTS

During a median follow-up of 13.7 years, 633 (8.7%) participants newly developed CKD. The fully adjusted hazard ratios (HR) with 95% confidence interval (CI) for incident CKD of the LPD and HPD groups compared with the NPD group were 1.49 (1.18-1.87) and 0.63 (0.45-0.87), respectively. The HR (95% CI) of the highest tertile group of plant protein intake for incident CKD was 0.72 (0.54-0.93), compared with that of the lowest tertile group. Similar trends were observed only in the non-DM subgroup, not in the DM subgroup.

CONCLUSION

Protein intake, especially plant proteins, was negatively associated with the incidence of new-onset CKD in middle-aged and older Korean adults.

Effectiveness of low-carbohydrate diets for long-term weight loss in obese individuals: A meta-analysis of randomized controlled trials

AIM

To assess whether low-carbohydrate (LC) diets are associated with differences in weight loss and well-being in people with obesity, and their cardiovascular and renal safety.

MATERIALS AND METHODS

A meta-analysis of randomized controlled trials longer than 3 months, retrieved through an extensive search on MedLine and Embase databases, comparing weight loss with LC and control diets in people with body mass index (BMI) greater than 30 kg/m2 , was conducted.

RESULTS

We retrieved 25 trials. Compared with controls, LC diets were associated with significant reduction of body weight at 3-4 (MD -2.59 [-3.93, -1.25] kg) and 6-8 months (MD -2.64 [-4.32, -0.95]), but no difference at 10-14 and 18-30 months, and significantly greater BMI reduction at 3-4 months (-1.66 [-2.70, -0.61] kg/m2 ), but not at other time points. Because only four trials reported data on renal function and psychological variables, renal safety and impact on well-being could not be assessed. Differences in fasting plasma glucose at any time point were not statistically significant. No significant differences in total or LDL cholesterol or blood pressure were found in the long term, whereas a long-term reduction of triglycerides (23.26 [-45.53, -0.98] mg/dl at 18-30 months), and increase of HDL cholesterol (MD 4.94 [0.30, 9.57] mg/dl at 18-30 months), were observed.

CONCLUSION

LC diets are associated with greater short-term weight loss than non-carbohydrate-restricted diets and a longer term favourable effect on cardiovascular risk factors. Further evidence on long-term efficacy and renal safety is needed before LC diets can be recommended as the preferred diets in obese people.

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.

Revisiting glomerular hyperfiltration and examining the concept of high dietary protein-related nephropathy in athletes and bodybuilders

PURPOSE OF REVIEW

High-protein diets (HPDs) are popular but their consequences for kidney health, especially among athletes and bodybuilders who typically maintain a high protein intake for a long time, have not been investigated. This review focused on recent studies of the association of HPD with long-term kidney health and the concept of high dietary protein-related nephropathy.

RECENT FINDINGS

Several long-term observational studies including large populations have reinforced the notion that HPDs are associated with a rapid decline of kidney function. An increase in renal blood flow and glomerular hyperfiltration caused by vasodilation, and increased levels of endocrine and paracrine factors (glucagon, IGF-1, prostanoids, and nitric oxide), facilitates the excretion of protein-derived nitrogenous waste. Inhibition of tubule-glomerular feedback and increased proximal tubular Na+ reabsorption after a HPD augment glomerular hyperfiltration and may trigger synthesis of proinflammatory cytokines and receptor for advanced glycation end-products (RAGE). Focal segmental glomerulosclerosis reported in association with anabolic steroid may indeed be a HPD nephropathy given that HPD results in progressive glomerulosclerosis, especially in remnant glomeruli or in diabetic kidney disease but can happen in any high-risk situation, such as solitary kidney and polycystic kidneys.

SUMMARY

HPD among athletes and bodybuilders in an extreme way across a long-term period may pose a risk to renal health including high incidence of HPD nephropathy.

Net Endogenous Acid Excretion and Kidney Allograft Outcomes

BACKGROUND AND OBJECTIVES

High dietary acid load may accelerate a decline in kidney function. We prospectively investigated whether dietary acid load is associated with graft outcomes in kidney transplant recipients, and whether venous bicarbonate mediates this association.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used data from 642 kidney transplant recipients with a functioning graft ≥1 year after transplantation. Net endogenous acid production was estimated using food frequency questionnaires and, alternatively, 24-hour urinary urea and potassium excretion to estimate net endogenous acid production. We defined the composite kidney end point as a doubling of plasma creatinine or graft failure. Multivariable Cox regression analyses, adjusted for potential confounders, were used to study the associations of dietary acid load with the kidney end point. We evaluated potential mediation effects of venous bicarbonate, urinary bicarbonate excretion, urinary ammonium excretion, titratable acid excretion, and net acid excretion on the association between net endogenous acid production and the kidney end point.

RESULTS

The median net endogenous acid production using food frequency questionnaires and net endogenous acid production using urinary excretion were 40 (interquartile range, 35-45) and 54 (interquartile range, 44-66) mEq/day, respectively. During a median follow-up of 5.3 years (interquartile range, 4.1-6.0), 121 (19%) participants reached the kidney end point. After multivariable adjustment, net endogenous acid production using food frequency questionnaires and net endogenous acid production using urinary excretion (per SD higher) were independently associated with higher risk for kidney end point (hazard ratio, 1.33; 95% confidence interval, 1.12 to 1.57, P=0.001 and hazard ratio, 1.44; 95% confidence interval, 1.24 to 1.69, P<0.001, respectively). Baseline venous bicarbonate mediated 20% of the association between net endogenous acid production using food frequency questionnaires and the kidney end point. Baseline venous bicarbonate, urinary ammonium excretion, and net acid excretion mediated 25%, -14%, and -18%, respectively, of the association between net endogenous acid production using urinary excretion and the kidney end point.

CONCLUSIONS

Higher dietary acid load was associated with a higher risk of doubling of plasma creatinine or graft failure, and this association was partly mediated by venous bicarbonate, urinary ammonium, and net acid excretion.

Pathogenesis of diabesity-induced kidney disease: role of kidney nutrient sensing

Diabetes kidney disease (DKD) is a major healthcare problem associated with increased risk for developing end-stage kidney disease and high mortality. It is widely accepted that DKD is primarily a glomerular disease. Recent findings however suggest that kidney proximal tubule cells (KPTCs) may play a central role in the pathophysiology of DKD. In diabetes and obesity, KPTCs are exposed to nutrient overload, including glucose, free-fatty acids and amino acids, which dysregulate nutrient and energy sensing by mechanistic target of rapamycin complex 1 and AMP-activated protein kinase, with subsequent induction of tubular injury, inflammation, and fibrosis. Pharmacological treatments that modulate nutrient sensing and signaling in KPTCs, including cannabinoid-1 receptor antagonists and sodium glucose transporter 2 inhibitors, exert robust kidney protective effects. Shedding light on how nutrients are sensed and metabolized in KPTCs and in other kidney domains, and on their effects on signal transduction pathways that mediate kidney injury, is important for understanding the pathophysiology of DKD and for the development of novel therapeutic approaches in DKD and probably also in other forms of kidney disease.

Protein Intake and Human Health: Implications of Units of Protein Intake

Understanding the health effects of protein intake is bedeviled by a number of factors, including protein quality and source. In addition, different units, including grams, grams per kilogram body weight (g/kg BW), and percent energy, may contribute to confusion about protein's effects on health, especially BW-based units in increasingly obese populations. We aimed to review the literature and to conduct a modeling demonstration of various units of protein intake in relation to markers of cardiometabolic health. Data from the Framingham Heart Study Offspring (n = 1847; 60.3 y; 62.5% women) and Third Generation (n = 2548; 46.2 y; 55.3% women) cohorts and the NHANES 2003-04 (n = 1625; 46.2 y; 49.7% women) and 2005-06 (n = 1347; 43.7 y; 49.5% women) cycles were used to model cross-sectional associations between 7 protein units (grams, percent energy, g/kg ideal BW, g/kg actual BW, BW-adjusted g/kg actual BW, g/kg lean BW, and g/kg fat-free BW) and 9 cardiometabolic outcomes (fasting glucose, systolic and diastolic blood pressure, total and HDL cholesterol, triglycerides, BMI, waist circumference, and estimated glomerular filtration rate). The literature review indicated the use of myriad units of protein intake, with differential results on cardiometabolic outcomes. The modeling demonstration showed units expressed in BW were confounded by BW, irrespective of outcome. Units expressed in grams, percent energy, and ideal BW showed similar results, with or without adjustment for body size. After adjusting for BW, results of units expressed in BW aligned with results of grams, percent energy, and ideal BW. In conclusion, protein intake in cardiometabolic health appears to depend on protein's unit of expression. Authors should be specific about the use of WHO (g/kg ideal BW) compared with US (g/kg actual BW) units, and ideally use gram or percent energy in observational studies. In populations where overweight/obesity are prevalent, intake based on actual BW should be reevaluated.

Modifiable Lifestyle Factors for Primary Prevention of CKD: A Systematic Review and Meta-Analysis

BACKGROUND

Despite increasing incidence of CKD, no evidence-based lifestyle recommendations for CKD primary prevention apparently exist.

METHODS

To evaluate the consistency of evidence associating modifiable lifestyle factors and CKD incidence, we searched MEDLINE, Embase, CINAHL, and references from eligible studies from database inception through June 2019. We included cohort studies of adults without CKD at baseline that reported lifestyle exposures (diet, physical activity, alcohol consumption, and tobacco smoking). The primary outcome was incident CKD (eGFR<60 ml/min per 1.73 m²). Secondary outcomes included other CKD surrogate measures (RRT, GFR decline, and albuminuria).

RESULTS

We identified 104 studies of 2,755,719 participants with generally a low risk of bias. Higher dietary potassium intake associated with significantly decreased odds of CKD (odds ratio [OR], 0.78; 95% confidence interval [95% CI], 0.65 to 0.94), as did higher vegetable intake (OR, 0.79; 95% CI, 0.70 to 0.90); higher salt intake associated with significantly increased odds of CKD (OR, 1.21; 95% CI, 1.06 to 1.38). Being physically active versus sedentary associated with lower odds of CKD (OR, 0.82; 95% CI, 0.69 to 0.98). Current and former smokers had significantly increased odds of CKD compared with never smokers (OR, 1.18; 95% CI, 1.10 to 1.27). Compared with no consumption, moderate consumption of alcohol associated with reduced risk of CKD (relative risk, 0.86; 95% CI, 0.79 to 0.93). These associations were consistent, but evidence was predominantly of low to very low certainty. Results for secondary outcomes were consistent with the primary finding.

CONCLUSIONS

These findings identify modifiable lifestyle factors that consistently predict the incidence of CKD in the community and may inform both public health recommendations and clinical practice.

Low-carbohydrate diets and type 2 diabetes treatment: a meta-analysis of randomized controlled trials

AIM

To assess whether LC diets are associated with long-term improvement in glycemic control and weight loss in people with T2DM, and their cardiovascular and renal safety.

METHODS

Meta-analysis of randomized controlled trials lasting more than 3 months, retrieved through extensive search on PubMed, Embase, ClinicalTrial.gov, Cochrane databases up to March 1st, comparing LC diets and balanced carbohydrate diets in people with T2DM.

RESULTS

We retrieved 37 trials, including 3301 patients. Average carbohydrate intake in LC diets was 36% of total energy. LC diets were associated with significant reduction of HbA1c at 3 months (MD - 0.17%, 95% CI - 0.27, - 0.07), no difference at 6 and 12 months, and significant increase at 24 months (MD 0.23%, 95% CI MD 0.02, 0.44). VLC diets were associated with significant HbA1c reduction at 3 and 6 months (MD - 0.43% - 0.60, - 0.26%, and MD - 0.40% 95% CI - 0.59, - 0.22, respectively), but not at 12 and 24 months. LC diets were associated with significant BMI reduction at 6 months (- 1.35 kg/m² 95% CI, - 2.18, - 0.52), but not at other time points. Only a minority of trials reported data on renal function, so renal safety could not be assessed. No significant differences in body weight, lipid profile, or blood pressure were found in the long term.

CONCLUSION

LC diets may produce small short-term improvements in HbA1c and weight, which are not maintained in the long term. Data on their renal safety are insufficient.

High-protein diet: A barrier to the nephroprotective effects of sodium-glucose co-transporter-2 inhibitors?

Glomerular hyperfiltration is a common finding in patients with diabetes and poor glycaemic control; whole-kidney hyperfiltration, with glomerular filtration rate (GFR) values above normal, should be differentiated from single nephron hyperfiltration, consequent to nephron loss and compensatory hyperfiltration of the remnant nephrons. This is the result of an imbalance between the vascular tone of the afferent and efferent arterioles. Hormonal influences and/or an impaired tubuloglomerular feedback (TGF) system, because of excessive sodium (Na⁺ ) and glucose reabsorption in the proximal tubule, contribute to determine hyperfiltration. Sodium-glucose co-transporter-2 inhibitors (SGLT2is), by decreasing Na⁺ reabsorption and increasing the delivery of Na⁺ to the macula densa, lead to normalization of TGF, and, consequently, decrease GFR (both whole and single nephron). High-protein diets are popular among patients with type 1 and type 2 diabetes; importantly, 80% of the amino acids are also reabsorbed in the proximal tubule of the nephron and are transported by symporters that use the electro-chemical gradient of Na⁺ . Indeed, an acute protein load is associated with increased Na⁺ reabsorption and an increase in GFR. Here, we hypothesize that high-protein diets, by increasing Na⁺ reabsorption and GFR, may offset the positive renal effects of SGLT2is.

The Effects of High-Protein Diets on Kidney Health and Longevity

Although high-protein diets continue to be popular for weight loss and type 2 diabetes, evidence suggests that worsening renal function may occur in individuals with-and perhaps without-impaired kidney function. High dietary protein intake can cause intraglomerular hypertension, which may result in kidney hyperfiltration, glomerular injury, and proteinuria. It is possible that long-term high protein intake may lead to de novo CKD. The quality of dietary protein may also play a role in kidney health. Compared with protein from plant sources, animal protein has been associated with an increased risk of ESKD in several observational studies, including the Singapore Chinese Health Study. Potential mediators of kidney damage from animal protein include dietary acid load, phosphate content, gut microbiome dysbiosis, and resultant inflammation. In light of such findings, adopting current dietary approaches that include a high proportion of protein for weight reduction or glycemic control should be considered with care in those at high risk for kidney disease. Given the possibility of residual confounding within some observational studies and the conflicting evidence from previous trials, long-term studies including those with large sample sizes are warranted to better ascertain the effects of high protein intake on kidney health.

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.

Dietary Protein: Mechanisms Influencing Hypertension and Renal Disease

PURPOSE OF REVIEW

This review will provide an in-depth coverage of the epidemiological and pre-clinical literature surrounding the role of dietary protein in hypertension, with a special emphasis on the history of our work on the Dahl salt-sensitive rat.

RECENT FINDINGS

Our studies have dedicated much effort into understanding the relationship between dietary protein and its effect on the development of salt-sensitive hypertension and renal injury. Our evidence over the last 15 years have demonstrated that both the source and amount of dietary protein can influence the severity of disease, where we have determined mechanisms related to immunity, the maternal environment during pregnancy, and more recently the gut microbiota, which significantly contribute to these diet-induced effects. Deeper understanding of these dietary protein-related mechanisms may provide insight on the plausibility of dietary modifications as future therapeutic avenues for hypertension and renal disease.

Dietary proteins and protein sources and risk of death: the Kuopio Ischaemic Heart Disease Risk Factor Study

BACKGROUND

Previous studies investigating protein intake in relation to mortality have provided conflicting results.

OBJECTIVE

We investigated the associations of dietary protein and protein sources with risk of disease death in the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor Study.

METHODS

The study population consisted of 2641 Finnish men, aged 42-60 y at baseline in 1984-1989. We estimated protein intakes with 4-d dietary records at baseline and collected data on disease deaths from the national Causes of Death Register. Cox proportional hazards regression models were used to estimate HRs and 95% CIs.

RESULTS

During the average follow-up of 22.3 y, we observed 1225 deaths due to disease. Higher intakes of total protein and animal protein had borderline statistically significant associations with increased mortality risk: multivariable-adjusted HR (95% CI) in the highest compared with the lowest quartile for total protein intake = 1.17 (0.99, 1.39; P-trend across quartiles = 0.07) and for animal protein intake = 1.13 (0.95, 1.35; P-trend = 0.04). Higher animal-to-plant protein ratio (extreme-quartile HR = 1.23; 95% CI: 1.02, 1.49; P-trend = 0.01) and higher meat intake (extreme-quartile HR = 1.23; 95% CI: 1.04, 1.47; P-trend = 0.01) were associated with increased mortality. When evaluated based on disease history at baseline, the association of total protein with mortality appeared more evident among those with a history of type 2 diabetes, cardiovascular disease, or cancer (n = 1094) compared with those without disease history (n = 1547) (P-interaction = 0.05 or 0.07, depending on the model). Intakes of fish, eggs, dairy, or plant protein sources were not associated with mortality.

CONCLUSIONS

Higher ratio of animal to plant protein in diet and higher meat intake were associated with increased mortality risk. Higher total protein intake appeared to be associated with mortality mainly among those with a predisposing disease. This trial was registered at clinicaltrials.gov as NCT03221127.

Dietary Protein Intake, Protein Energy Wasting, and the Progression of Chronic Kidney Disease: Analysis from the KNOW-CKD Study

Studies on the effect of dietary protein intake (DPI) on chronic kidney disease (CKD) progression, along with the potential hazard of protein-energy wasting (PEW), are scarce. We evaluated the association between DPI and kidney function both cross-sectionally and longitudinally, particularly emphasizing the role of PEW, in a large-scale, observational, multicenter, prospective study. We enrolled 1572 patients with non-dialysis CKD between 2011 and 2016. CKD progression was defined by a >50% estimated glomerular filtration rate (eGFR) decrease, serum creatinine doubling, or dialysis initiation. A Cox proportional hazard regression analysis was conducted. During the mean follow-up period of 41.6 months, CKD progression was observed in 296 patients. Cross-sectionally, increased DPI was significantly associated with increased eGFR. Similarly, increased DPI tertile was significantly associated with increased renal survival in a Kaplan–Meier curve analysis. In the multivariate Cox proportional hazard regression analysis, the statistical significance of the DPI tertile group in CKD progression was lost when PEW-related variables were added as covariates. In penalized spline curve analysis, the adjusted odds ratio of PEW significantly increased as DPI decreased. DPI, per se was not a major determinant of CKD progression. An intimate association between reduced DPI and PEW may be a more important predictor of CKD progression than DPI.

Educational level and risk of chronic kidney disease: longitudinal data from the PREVEND study

Background

The longitudinal association between low education and chronic kidney disease (CKD) and its underlying mechanisms is poorly characterized. We therefore examined the association of low education with incident CKD and change in kidney function, and explored potential mediators of this association.

Methods

We analysed data on 6078 participants from the community-based Prevention of Renal and Vascular End-stage Disease study. Educational level was categorized into low, medium and high (&lt; secondary, secondary/equivalent, &gt; secondary schooling, respectively). Kidney function was assessed by estimating glomerular filtration rate (eGFR) by serum creatinine and cystatin C at five examinations during ∼11 years of follow-up. Incident CKD was defined as new-onset eGFR &lt;60 mL/min/1.73 m2 and/or urinary albumin ≥30 mg/24 h in those free of CKD at baseline. We estimated main effects with Cox regression and linear mixed models. In exploratory causal mediation analyses, we examined mediation by several potential risk factors.

Results

Incident CKD was observed in 861 (17%) participants. Lower education was associated with higher rates of incident CKD [low versus high education; hazard ratio (HR) (95% CI) 1.25 (1.05–1.48), Ptrend = 0.009] and accelerated eGFR decline [B (95% CI) −0.15 (−0.21 to −0.09) mL/min/1.73 m2/year, Ptrend &lt; 0.001]. The association between education and incident CKD was mediated by smoking, potassium excretion, body mass index (BMI), waist-to-hip ratio (WHR) and hypertension. Analysis on annual eGFR change in addition suggested mediation by magnesium excretion, protein intake and diabetes.

Conclusions

In the general population, we observed an inverse association of educational level with CKD. Diabetes and the modifiable risk factors smoking, poor diet, BMI, WHR and hypertension are suggested to underlie this association. These findings provide support for targeted preventive policies to reduce socioeconomic disparities in kidney disease.