Importance and benefits of dietary sodium restriction in the management of chronic kidney disease patients: experience from a single Chinese center

Aim  

Several studies have suggested that sodium intake may affect blood pressure (BP), proteinuria, and intrarenal transforming growth factor-β1 (TGF-β1) production in patients and animal models with chronic kidney disease (CKD). The Chinese population has a high prevalence of CKD and is well known for consuming salty foods. This study will investigate the role of dietary sodium intake on BP control among non-dialysis Chinese CKD patients.     

Is it the low-protein diet or simply the salt restriction?

Dietary factors, such as salt and protein intake, may play an important role in the progression of kidney disease. Consequently, dietary manipulations of these constituents are of interest both in experimental models of kidney disease and in clinical trials with patients with chronic kidney disease to assess whether modification of these exposures will result in a stabilization of disease progression.     

Salt intake and hypertension therapy

Hypertension is a risk factor for cardiovascular and renal organ damage. Environmental conditions affect the development of high blood pressure (BP), although genetic influences are also important. Current international guidelines recommend reducing dietary sodium to no more than 100 mmol (about 2.4 g sodium or approximately 6 g salt) per day to prevent BP rising; the current intake of sodium in industrialized countries is approximately double the recommended amount. Clinical trials (DASH and TOHP studies) have shown that dietary factors are fundamental in the prevention and control of BP. Low dietary sodium intake is particularly effective in preventing hypertension in subjects with an increased risk such as the overweight, borderline hypertensives or the elderly. A low-salt diet combined with anti-hypertensive therapies facilitates BP reduction independent of race. The hypotensive effect of calcium channel blockers is less dependent on salt intake than other drugs, such as ACE inhibitors or diuretics. Reduced sodium intake associated with other dietary changes (such as weight loss, and increasing potassium, calcium and magnesium intake) are important instruments for the prevention and therapy of hypertension.     

Adherence to Dietary Recommendations Measured by Smartphone-based Recipe Nutrition Calculator in Kidney Transplant Patients

BackgroundDietary restriction of protein, salt, and energy is recommended to prevent lifestyle related diseases, proteinuria, and graft dysfunction in kidney transplant patients. It is useful if the patients can evaluate meal components by themselves for each meal.Patients and methodsA total of 26 maintenance-phase kidney transplant patients were included in the study. The mean age, sex, body mass index, number of years post-transplantation, creatinine clearance, and 24-hour urinary excretion (24 UE) of protein were recorded on a medical chart. Estimated daily protein and salt oral intake were calculated from 24 UE of nitrogen and sodium, respectively. We compared these laboratory results and patients’ self-reported dietary intake using a smartphone-based recipe nutrition calculator (SRNC).ResultsEstimated daily protein and salt oral intake calculated from 24 UE of nitrogen and sodium were 55.4 ± 12.9 g/d and 8.5 ± 3.1 g/d, respectively. Estimated daily protein and salt oral intake measured by SRNC were 52.4 ± 13.8 g/day and 6.5 ± .9 g/day, respectively. The results of estimated daily protein and salt oral intake measured by SRNC were correlated to those calculated from 24 UE (R² = .287 and .217, respectively).ConclusionsThe results of estimated daily protein and salt oral intake measured by SRNC were correlated to those calculated from 24 UE in maintenance-phase kidney transplant patients. SRNC was useful as a measurement modality to evaluate the adherence to dietary guidance. Dietary therapy for these patients may have the potential to improve kidney graft function and survival.     

Survival disparities within American and Israeli dialysis populations: learning from similarities and distinctions across race and ethnicity

There are counterintuitive but consistent observations that African American maintenance dialysis patients have greater survival despite their less favorable socioeconomic status, high burden of cardiovascular risks including hypertension and diabetes, and excessively high chronic kidney disease prevalence. The fact that such individuals have a number of risk factors for lower survival and yet live longer when undergoing dialysis treatment is puzzling. Similar findings have been made among Israeli maintenance dialysis patients, in that those who are ethnically Arab have higher end-stage renal disease but exhibit greater survival than Jewish Israelis. The juxtaposition of these two situations may provide valuable insights into racial/ethnic-based mechanisms of survival in chronic diseases. Survival advantages of African American dialysis patients may be explained by differences in nutritional status, inflammatory profile, dietary intake habits, body composition, bone and mineral disorders, mental health and coping status, dialysis treatment differences, and genetic differences among other factors. Prospective studies are needed to examine similar models in other countries and to investigate the potential causes of these paradoxes in these societies. Better understanding the roots of racial/ethnic survival differences may help improve outcomes in both patients with chronic kidney disease and other individuals with chronic disease states.     

Dietary recommendations for obese patients with chronic kidney disease

For optimal management of chronic kidney disease (CKD), dietary modification should be an integral part of patient care. Dietary considerations for obese patients with CKD are numerous and complicated and involve modification of intake of calories, protein, fat, phosphorus, and electrolytes. General principles for dietary management of obese patients include (1) ensuring adequate monitoring of nutritional status through assessment of diet, nutrition-related laboratory parameters, and anthropometrics; (2) creation of an individualized diet plan that meets clinical guidelines and has favorable effects on obesity-related conditions such as blood pressure and lipids; (3) careful attention to patients' food choices, portion size, and food-preparation methods; (4) recommending adjustment of overall energy intake to promote weight loss, yet maintain good nutritional status; and (5) modification of diet as the patient's nutritional status changes and CKD progresses. The basic objectives of dietary modification are to lighten the excretory load of products of metabolism and to help the kidney maintain normal equilibrium of the body's internal environment. Dietary modifications must be individualized and appropriate to the stage of CKD. This review describes dietary factors important in optimizing nutritional status of obese patients with CKD. Additionally, current clinical practice guidelines and strategies for meeting them are discussed.     

Dietary acid reduction with fruits and vegetables or bicarbonate attenuates kidney injury in patients with a moderately reduced glomerular filtration rate due to hypertensive nephropathy

The neutralization of dietary acid with sodium bicarbonate decreases kidney injury and slows the decline of the glomerular filtration rate (GFR) in animals and patients with chronic kidney disease. The sodium intake, however, could be problematic in patients with reduced GFR. As alkali-induced dietary protein decreased kidney injury in animals, we compared the efficacy of alkali-inducing fruits and vegetables with oral sodium bicarbonate to diminish kidney injury in patients with hypertensive nephropathy at stage 1 or 2 estimated GFR. All patients were evaluated 30 days after no intervention; daily oral sodium bicarbonate; or fruits and vegetables in amounts calculated to reduce dietary acid by half. All patients had 6 months of antihypertensive control by angiotensin-converting enzyme inhibition before and during these studies, and otherwise ate ad lib. Indices of kidney injury were not changed in the stage 1 group. By contrast, each treatment of stage 2 patients decreased urinary albumin, N-acetyl β-D-glucosaminidase, and transforming growth factor β from the controls to a similar extent. Thus, a reduction in dietary acid decreased kidney injury in patients with moderately reduced eGFR due to hypertensive nephropathy and that with fruits and vegetables was comparable to sodium bicarbonate. Fruits and vegetables appear to be an effective kidney protective adjunct to blood pressure reduction and angiotensin-converting enzyme inhibition in hypertensive and possibly other nephropathies.     

Protein and Energy Intake in Advanced Chronic Kidney Disease: How Much is Too Much?

Uremic wasting is strongly associated with increased risk of death and hospitalization events in patients with advanced chronic kidney disease (CKD). Recent evidence indicates that patients with advanced chronic kidney disease are prone to uremic wasting due to several factors, which include the dialysis procedure and certain comorbid conditions, especially chronic inflammation and insulin resistance or deficiency. While the catabolic effects of dialysis can be readily avoided with intradialytic nutritional supplementation, there are no established alternative strategies to avoid the catabolic consequences of comorbid conditions other than treatment of their primary etiology. To this end, there is no indication that simply increasing dietary protein and energy intake above the required levels based on level of kidney disease is beneficial in patients with advanced chronic kidney disease. However, aside from the potential adverse effects such as uremic toxin production, dietary protein and energy intake in excess of actual needs might be beneficial in maintenance dialysis patients as it may lead to weight gain over time. Clearly, the role of obesity in advanced uremia needs to be examined in detail prior to making any clinically applicable recommendations, both in terms of 'low' and 'high' dietary protein and energy intake.     

Relationship between dietary phosphorus intake and nutritional status and calcium and phosphorus metabolism in patients with chronic kidney disease

Objective To evaluate the dietary phosphorus intake of non-dialysis patients with chronic kidney disease (CKD) 3-5 stage, and to explore the relationship between dietary phosphorus intake, nutritional status, and calcium and phosphorus metabolism. Methods A cross-sectional study was conducted. Non-dialysis patients of CKD 3-5 stage in Huashan Hospital outpatient clinic were selected. Three-day dietary diaries, anthropometric indicators, subjective global assessment (SGA) scores, blood and 24-hour urine biochemical indicators were collected. According to the median dietary phosphorus intake (873 mg/d), the patients were divided into high phosphorus intake group (≥ 873 mg/d) and low phosphorus intake group (＜873 mg/d). The differences of characteristics, anthropometric indicators, SGA scores, blood and urine biochemical indicators between the two groups were compared. Multivariate linear regression analysis was used to analyze the correlation between dietary phosphorus intake and different kinds of food intake. Results A total of 118 patients were enrolled. The daily energy intake was (25.48±4.45) kcal/kg, protein intake was (0.88±0.22) g/kg and phosphorus intake was (862.85±233.02) mg/d. There were no significant differences in body mass index and SGA scores between high phosphorus intake group and low phosphorus intake group. The waist circumference, hip circumference, waist-hip ratio and leg circumference of male patients in high phosphorus intake group were higher than those in low phosphorus intake group (all P＜0.05). There were no significant differences in anthropometric indicators between the two groups of female patients. The serum levels of intact parathyroid hormone (iPTH), sodium, triglyceride, blood RBC count, alanine aminotransferase, 24-hour urine urea nitrogen, 24-hour urine creatinine and 24-hour urine phosphate in the high phosphorus intake group were higher than those in the low phosphorus intake group (all P＜0.05). Multivariate regression analysis showed that pork and chicken contributed the most to dietary phosphorus intake, followed by fish and dairy. Conclusions The daily dietary phosphorus intake of non-dialysis of CKD 3-5 stage patients is slightly higher than the recommended intake. The increase of dietary phosphorus intake may lead to the increase of serum iPTH and sodium levels. Proper control of dietary phosphorus intake will not impair the nutritional status of CKD patients.     

An integrated approach to care for patients with chronic kidney disease

Although the Kidney Disease Outcomes and Quality Initiative (K/DOQI) guidelines serve to integrate the multiple stages of chronic kidney disease (CKD), in practice, the treatment of kidney disease over its progressive course may be somewhat fragmented. Because the provision of integrated care across the stages of kidney disease, is likely to be advantageous for both patients and care providers, a conceptual framework which graphically depicts the complex and chronic nature of kidney disease may prove useful. The Life Options Rehabilitation Advisory Council (LORAC) proposes a cycle diagram to reflect the chronicity and complexity of kidney disease and to emphasize a holistic perception of kidney disease from its inception to the worst-case scenario outcome of kidney failure [corrected]. The kidney disease cycle conceptualization can serve as a patient teaching aid and as a reminder of the communication, collaboration, and cooperation that are required among primary care physicians and practitioners in each of the specialty areas that address the spectrum of kidney disease.     

Renal 'salt wasting' despite apparently normal renal, adrenal and central nervous system function.

The inability of the kidney to conserve sodium appropriately in response to a restricted sodium intake is reported in a subject who had entirely normal renal and adrenal function and no evidence of central nervous system disease. Subsequent transplantation of his left kidney to his son afforded a unique opportunity to assess renal sodium conservation in each kidney separately: both the patient and his son were unable to achieve balance in response to dietary sodium restriction after transplantation, indicating that the sodium wasting was due to a process intrinsic to both kidneys. The assessment of intrarenal hemodynamics with xenon-133 washout prior to nephrectomy provided insight into the role of intrarenal hemodynamics in the maintenance of sodium homeostasis in man. The xenon washout curve failed to disclose an identifiable second most rapid exponential (CII). This finding, in concert with previous studies demonstrating that diuretic agents with a primary action in the ascending limb of the loop of Henle caused a marked slowing of CII flow, raises the possibility that limited perfusion in the outer medulla of the kidney may be rate-limiting for sodium conservation in man.     

Energy Balance in Advanced Chronic Kidney Disease and End‐Stage Renal Disease

Energy intake, resting energy expenditure, and energy expended for physical activity (EEPA) are components of energy balance that may be disrupted by a number of disorders and clinical conditions commonly present in advanced chronic kidney disease (CKD) and end‐stage renal disease (ESRD). Energy intake of patients with CKD has been consistently lower than the recommended intake in multiple reports. On the other hand, while reduced energy intake due to anorexia may be applicable for ESRD patients with overt protein‐energy wasting, it is potentially unrealistic for overweight or obese subjects who are able to maintain their body weight. Studies on resting energy expenditure have provided mixed results, most likely as a consequence of differences in the population characteristics, clinical conditions, and stage of the disease. Finally, although there is lack of specific studies on EEPA, there is evidence that ESRD patients, particularly those undergoing hemodialysis are in general less active than sedentary healthy individuals. These observations may raise questions regarding the accuracy of dietary reports and the uncertainties related to the energy requirements, optimal dietary energy intake, and recommendations for physical activity in these patients.     

Effect of salt intake on progression of chronic kidney disease

PURPOSE OF REVIEW: The attempt of this review is to bring into focus the potential role of dietary salt intake in progression of chronic kidney disease. RECENT FINDINGS: Ongoing work has elucidated a role for dietary salt intake in modulating intrarenal production of transforming growth factor-beta1. The mechanism is independent of angiotensin II and systemic blood pressure and involves activation of vascular endothelium by dietary salt intake with release of this growth factor. In this model, transforming growth factor-beta1 serves an autacoid function by stimulating nitric oxide production by the endothelium. In turn, endothelium-derived nitric oxide modulates production of this growth factor. The model further predicts that individuals who have lost the requisite endothelial cell flexibility to adapt to this environmental stress (a high salt diet) are potentially at increased risk of developing end-organ damage from excess salt intake. Animal and human studies are presented to support this working hypothesis. SUMMARY: Overproduction of transforming growth factor-beta1 permits excess biological activity of this important fibrogenic growth factor with subsequent development or acceleration of vascular and kidney damage. In patients with diseases whose pathogenesis is related to excess production of transforming growth factor-beta1, such as chronic allograft nephropathy and diabetic nephropathy, increased salt intake may hasten loss of function, particularly if nitric oxide production does not increase. The role that endothelial cell plasticity plays in altering vascular tone and renal function, especially in response to changes in dietary salt intake, should be examined further in chronic kidney disease.     

The impact of dietary oxalate on kidney stone formation

The role of dietary oxalate in calcium oxalate kidney stone formation remains unclear. However, due to the risk for stone disease that is associated with a low calcium intake, dietary oxalate is believed to be an important contributing factor. In this review, we have examined the available evidence related to the ingestion of dietary oxalate, its intestinal absorption, and its handling by the kidney. The only difference identified to date between normal individuals and those who form stones is in the intestinal absorption of oxalate. Differences in dietary oxalate intake and in renal oxalate excretion are two other parameters that are likely to receive close scrutiny in the near future, because the research tools required for these investigations are now available. Such research, together with more extensive examinations of intestinal oxalate absorption, should help clarify the role of dietary oxalate in stone formation.     

Salt: its role in chronic kidney disease.

Few controversies in medicine have such a long history as that of whether salt is identifiably dangerous or not dangerous. The most common reported association between excess dietary salt intake and clinical outcome has been in the field of hypertension, but dietary sodium intake mediates effects that go far beyond, and are independent of, extracellular fluid expansion and elevation in blood pressure. For nephrologists, clinical trials that demonstrate no negative outcome of a high salt diet in the general population are thus not particularly assuasive, because patients with chronic kidney disease (CKD) represent an entity that is by no means comparable to the general population. This review takes a look at the challenges associated with salt balance in CKD patients (particularly at K/DOQI stage 5), followed by a summary of current concepts believed to play a part in salt-mediated pathophysiology, and the conclusion, based on the present state of scientific knowledge, that it appears advisable to advocate low dietary salt intake in this patient population.     

Investigation of common Indian edible salts suitable for kidney disease by laser induced breakdown spectroscopy

Salt is an essential and important dietary mineral for maintaining life. Currently, the issue of the potential benefit or damage from salt intake in chronic kidney disease patients is controversial. The attempt of this article is to bring into focus the potential role of elements particularly sodium, Na, and potassium, K, which are the main constituents of dietary salts, in kidney patients by using laser-induced breakdown spectroscopy (LIBS). LIBS spectra of different salt samples have been recorded in the spectral region 200–500 nm with spectral resolution 0.1 nm and in the spectral region 200–900 nm with spectral resolution 0.75 nm. Quantitative elemental study was carried out to determine the constituents of different types of common Indian edible salts by using the calibration-free LIBS method. Our experimental results demonstrate that Saindha salt (commonly known as rock salt) is more beneficial than other edible salts for patients suffering from chronic kidney disease. The results of the quantitative elemental analysis of the salts obtained from LIBS measurements are also compared to atomic absorption spectroscopy (AAS).     

Improvement in the Care of Patients With Kidney Transplant Failure: Recommendations of the Spanish Society of Nephrology

Although long-term outcomes have improved, graft loss caused by chronic allograft nephropathy remains an important obstacle. This situation, together with the progressive increase in the number of renal transplant patients, means that the population of transplant patients readmitted to a dialysis program will be progressively greater. The variable mortality rates among patients starting dialysis after graft loss are consistently higher than those observed among patients with functioning grafts or on dialysis treatment. However, the manner in which the management of chronic kidney disease patients in the transplant setting differs from that of patients with native kidney disease who display a similar degree of renal dysfunction is not known. Many patients in stages 4T–5T have chronic kidney disease-related complications that fall below the targets established for nontransplant chronic kidney disease subjects. A limited number of studies have evaluated patients returning to dialysis after graft failure. The distinct guidelines in the setting of transplantation have not analyzed this important aspect. From this premise, a working group of the Spanish Society of Nephrology specialying in the field of kidney transplantation and dialysis reviewed each clinical aspect of care of kidney transplant patients with renal failure returning to dialysis, yielding this consensus document to optimize management.