Fluid and nutrient intake and risk of chronic kidney disease

The Significance of Renal Impairment in Children with Eating Disorders

Background: Eating disorders have previously been associated with renal impairment. Low muscle mass reduces serum creatinine used for the calculation of the estimated glomerular filtration rate (eGFR), leading to overestimation of renal function. To solve this problem, the development of a tool to detect renal impairment in individual patients with a specific muscle mass is required to individualize risk assessment for further management. The objectives of our study were as follows: To investigate the percentage drop in creatinine (pdCr) during rehydration as a new indicator of renal dysfunction not dependent on muscle mass and to investigate a correlation between cardiovascular function and fluid management with renal function. Methods: In a 5-year retrospective cohort study of all consecutive children admitted because of an eating disorder, renal function expressed as eGFR on admission and as pdCr between admission and the lowest creatinine level was analysed in relation to cardiovascular parameters and fluid management. Results: We included 29 patients. The mean age was 13.4 years. A pdCr after admission was noted in 26/29 (89.7%). The eGFR was <90 in 15 (65%) and improved to >90 in 13/15 (86.6%). In patients with a fluid management plan, there was a median of 18.6% for those with pdCr and 6.4% (p = 0.02) for those without. Renal dysfunction was not related to cardiovascular parameters. Conclusions: The majority of patients with an eating disorder had renal impairment. PdCr was more sensitive in the detection of renal impairment in individual patients compared to eGFR.

Water/fluid intake in Kıdney transplant recipients: An underrated topic

Although kidney transplantation (KT) is the best treatment option for end-stage kidney disease, long-term complications such as chronic kidney allograft dysfunction and cardiovascular disorders are observed. To decrease these complications, preventive measures must be applied in kidney transplant recipients (KTRs). One of these common measures is the increase of water/fluid intake although this is not evidence-based practice. Indeed, surprisingly very limited studies evaluated the impact of increased water/fluid intake on graft function, with small number of KTRs and short term follow-up. We suggest that the water/fluid intake should be personalized based on baseline graft function, time onset after KT (which water homeostasis changes), presence of hyponatremia and hypervolemia, concomitant medications, and patient willingness. Methods for estimating water/fluid intake (direct measurement, 24-h urine volume measurement, urine osmolarity) has both advantages and drawbacks and the best method has not been identified. Increase of water/fluid intake in specific conditions (in hot, and humid weather, before exercise, during Ramadan fasting) or in distinct KTRs (KTRs with de novo nephrolithiasis, frequent urinary tract infections) is not tested. Furthermore, the relationship between water/fluid intake and major cardiovascular adverse events are not known. There is no doubt that minimum amount of water/fluid intake is necessary for graft function (the amount is not known) but there is no evidence for a particular target level of water/fluid intake. In the current review, we summarize the studies assessing fluid/water intake in KTR, explained the pathophysiologic basis of water disorders in early period of KT and late after KT, elucidate conflicts and unknown issues of water intake in KTRs and suggest future research needs.

Association between hydration status and the risk and all-cause mortality of diabetic kidney disease

BACKGROUND

This cohort study aimed to explore the relationship between hydration status and the risk of diabetic kidney disease (DKD) as well as all-cause death in DKD patients.

METHODS

Weighted univariable and multivariable logistic regression models were used to explore the association between hydration status and DKD risk in diabetic population while weighted univariable and multivariable Cox regression models were used to identify the association between hydration status and all-cause mortality in DKD patients. Kaplan-Meier curve was plotted to present the survival probability of patients with different hydration status. Estimates were presented as odds ratio (OR), and hazard ratio (HR) with 95% confidence interval (CI).

RESULTS

The mean follow-up time was 79.74 (±1.89) months. There were 2041 participants with DKD, and 2889 participants without. At the end of the follow-up, 965 participants were alive. The risk of DKD was increased as the increase of osmolarity level (OR = 1.07, 95%CI: 1.05-1.08). The elevated risk of DKD was observed in patients with impending dehydration (OR = 1.49, 95%CI: 1.19-1.85) or current dehydration (OR = 2.69, 95%CI: 2.09-3.46). The association between increased osmolarty level and elevated risk of all-cause mortality in DKD patients was statistically different (HR = 1.02, 95%CI: 1.01-1.03). Current dehydration was correlated with increased all-cause mortality risk in DKD patients (HR = 1.27, 95%CI: 1.01-1.61). Compared to DKD patients with normal hydration, the survival probability of DKD patients with current dehydration was significant lower (p < 0.001).

CONCLUSION

Increased osmolarity level was associated with increased risk of DKD and elevated risk of all-cause mortality in DKD patients.

Causal relationship between dietary intake and IgA nephropathy: a Mendelian randomization study

Objective

Previous studies have reported that dietary intake is associated with immunoglobulin A nephropathy (IgAN). However, the causal relationship remains unknown. Based on publicly available genome-wide association study (GWAS) data, we conducted a two-sample Mendelian randomization (MR) analysis to assess the causal association between 26 dietary exposures and IgAN.

Methods

Five methods, including inverse variance weighting (IVW), MR-Egger regression, weighted median, simple mode, and weighted mode, were applied in the MR analysis. To identify the presence of horizontal pleiotropy, we used the MR-Egger intercept test and MR pleiotropy residual sum and outlier (MR-PRESSO) global test. Cochran's Q statistics were used to assess instrument heterogeneity. We conducted sensitivity analysis using the leave-one-out method.

Results

Finally, the results indicated alcohol intake frequency (odds ratio [OR] (95% confidence interval [CI]) = 1.267 (1.100-1.460), p = 0.0010295) was a risk factor of IgAN, while cheese intake (OR (95% CI) = 0.626 (0.492-0.798), p = 0.0001559), cereal intake (OR (95% CI) = 0.652 (0.439-0.967), p = 0.0334126), and sushi intake (OR (95% CI) = 0.145 (0.021-0.997), p = 0.0497) were protective factors of IgAN. No causal relationship was found between IgAN and the rest of the dietary exposures.

Conclusion

Our study provided genetic evidence that alcohol intake frequency was associated with an increased risk of IgAN, while cheese, cereal, and sushi intake were associated with a decreased risk of IgAN. Further investigation is required to confirm these results.

Low daily water intake profile-is it a contributor to disease?

Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration (UD; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusion criteria: English language, full-text, peer reviewed, no restriction on research design, and three publications minimum. Initially, 3,903 articles were identified based on their titles and abstracts. Evaluations of full length .pdf versions identified 96 studies that were acceptable for inclusion. We concluded that the evidence is insufficient or conflicting for seven disorders or diseases (i.e. suggesting the need for additional clarifying research) and it is lacking for all-cause mortality. Differential characterizations among women and men have been reported in the results of nine studies involving five diseases. Finally, the evidence for associations of LOW or UD is strong for both kidney stones and type 2 diabetes with hyperglycemia. This suggests that great public health value (i.e. reduced disease risk) may result from increased daily water intake-a simple and cost-effective dietary modification.

Long-term association between water intake and kidney function in a population at high cardiovascular risk

OBJECTIVES

The evidence on water intake in the prevention of kidney function decline is scarce at population level in well-being individuals at high cardiovascular risk. Therefore, we aimed to longitudinally evaluate the associations between total water intake and subtypes and kidney function, through estimated-Glomerular Filtration Rate (eGFR).

METHODS

Three-year prospective analysis conducted in 1986 older adults (aged 55-75 year) with overweight/obesity and metabolic syndrome from the PREDIMED-Plus study. Water intake was assessed using validated beverage and food frequency questionnaires. Serum creatinine-based eGFR (SCr-based eGFR; ml/min/1.73 m2) was estimated using the CKD-EPI equation at baseline, one-year and 3-years of follow-up. Mixed-effects linear regression models were fitted to evaluate the associations between baseline total water intake and subtypes, and SCr-based eGFR over 3-years of follow-up.

RESULTS

Participants in the highest baseline tertile of total water intake, plain water and water from all fluids showed a lower decrease in SCr-based eGFR after 3-years of follow-up, compared to those in the lowest tertile. Participants with the highest tap water consumption showed a lower SCr-based eGFR decline after 1-year and 3-years of follow-up, in comparerd to participants in the lowest intake category (T3 vs. T1: β: 1.4 ml/min/1.73 m2; 95%CI: 0.5-2.3, β: 1.0; 95%CI: 0.1-2.0, respectively).

CONCLUSIONS

Plain water rather than other water sources, and especially tap water, was associated with lower kidney function decline assessed through eGFR over 3-years of follow-up, in older individuals at high cardiovascular risk.

TRIAL REGISTRATION

ISRCTN89898870. Retrospectively registered on 24 July 2014.

Risk factors associated with indicators of dehydration among migrant farmworkers

OBJECTIVE

Farmworkers are at increased risk of adverse health outcomes related to occupational heat exposure and inadequate access to water, shade, or rest breaks. Presently, there is a dearth of studies examining the prevalence of dehydration and related factors in U.S. farmworkers. Our objectives were to characterize hydration status during typical workdays and to identify risk factors associated with increased dehydration in migrant farmworkers employed in Florida.

METHODS

Urine samples were collected and analyzed for urine specific gravity (USG) 2-3 times per person per day over five days in May 2021 and 2022. Data collection included demographic characteristics, wet-bulb-globe-temperature (WBGT), and information on working conditions (task type, duration, and crop units harvested), fluid intake, clothing worn, and heat safety behaviors. Multivariable mixed regression models were used to evaluate risk factors associated with change in USG levels (continuous) during a work shift.

RESULTS

A total of 111 farmworkers participated in this study providing 1020 cumulative USG measurements, of which 96.8% of end-of-shift USG samples were above 1.020 indicating potential dehydration. In multivariable models, dehydration assessed using change in USG levels significantly declined with age (β = -0.078; 95%CI: 0.150, -0.006) but showed significant increase with body mass index (β = 0.016; 95%CI: 0.003, 0.028), WGBT (β = 0.054; 95%CI:0.044, 0.064), mean shift duration, and state of primary residence. We did not find significant associations of dehydration with type of clothing worn, intake of employer-provided water, or crop units harvested during a shift in this sample of farmworkers.

CONCLUSION

Our findings underscore the need for additional research to evaluate adverse outcomes related to dehydration and to better understand recovery patterns from chronic dehydration across workweeks and harvest seasons in migrant farmworkers.

Sodium and water dynamics in the progression of chronic kidney disease: mechanisms and clinical significance

AIM

Lifestyle modifications can postpone the progression of chronic kidney disease toward its terminal stage. This mini-review aims to explore the impact of salt and water intake on the progression of chronic kidney disease (CKD) and provide insights into the optimal consumption levels to preserve the glomerular filtration rate.

METHODS

We reviewed relevant literature to examine the association between salt and water consumption and CKD progression. Our analysis includes discussions on the pathophysiology, findings from clinical trials, and recommended intake guidelines.

RESULTS

Sodium intake, often linked to cardiovascular risk and CKD progression, has shown a complex J-shaped association in some studies, leading to uncertainty about the ideal salt intake level. Sodium and fluid retention are key factors contributing to hypertension, a well-established risk factor for CKD progression. Low-sodium diets have demonstrated promise in reducing blood pressure and enhancing the effects of renin-angiotensin-aldosterone system inhibitors in non-dialysis CKD patients. However, a debate persists regarding the independent effect of salt restriction on CKD progression. Despite medical recommendations, salt consumption remains high among CKD patients. Additionally, the role of water consumption in CKD remains controversial despite its established benefits for CKD prevention in the general population.

CONCLUSION

Lifestyle modifications involving salt and water intake can influence the progression of CKD. While low-sodium diets have shown potential for mitigating hypertension and proteinuria in non-dialysis CKD patients, their independent impact on CKD progression warrants further investigation. The role of water consumption in CKD remains uncertain, and there is a need for additional research in this area. Clinicians should consider individualized dietary recommendations for CKD patients to help preserve the glomerular filtration rate and improve overall outcomes.

Predictors of Water Turnover in Older Adults: A Doubly Labeled Water- and Triaxial Accelerometer-Based Study

BACKGROUND

Water is one of the most essential nutrients for life. The water turnover (WT), total body water (TBW), and total energy expenditure (TEE) can be measured using the doubly labeled water (DLW) method. WT and TBW are lower in older adults than in young adults, and the former are susceptible to dehydration, necessitating to identify predictors of the WT in older adults.

OBJECTIVES

The current study aimed to examine the association between WT and physical activity, physical function, and body composition in Japanese adults aged ≥65 y and identify predictors for WT in this population.

METHODS

This study enrolled 133 older adults (women, n = 61; men, n = 72) aged 65-88 y. WT, TBW, TEE, fat-free mass (FFM), and percent body fat (%Fat) were determined using the DLW method. The fitness age score (FAS) was obtained from 5 physical fitness tests. Physical activity and the step count were assessed using a previously validated triaxial accelerometer. Multiple regression analyses were performed with WT as the dependent variable.

RESULTS

WT was positively associated with weight, physical activity level (PAL), moderate-vigorous physical activity, and TEE, and negatively associated with sedentary behavior. We examined potential predictors for WT using age, sex, height, weight, FFM, %Fat, TEE, PAL, and FAS in older Japanese adults.

CONCLUSIONS

Our results confirmed that age, sex, weight, FFM, TEE, and PAL are the potential predictors of WT in older Japanese adults aged ≥65 y.

Association between dietary diversity and chronic kidney disease in community-dwelling older adults

OBJECTIVE

The present study examined whether dietary diversity is associated with chronic kidney disease (CKD) in community-dwelling older Japanese adults.

METHODS

Participants comprised 8,195 older adults (mean age was 74.0 ± 5.6 years; 42.7% were men) in this cross-sectional study. In this study, CKD was defined as estimated Glomerular Filtration Rate (eGFR) < 45 mL/min/1.73 m2. Diet variety was assessed using the Food Frequency Score (FFS) (maximum, 30 points). The FFS assessed the one-week consumption frequency of ten foods (meat, fish/shellfish, eggs, milk, soybean products, green & yellow vegetables, potatoes, fruits, seafood, and fats & oil). Participants with an FFS of 16 or fewer points were defined as having low dietary diversity.

RESULTS

The prevalence of CKD was 376 (4.6%), and the low dietary diversity group had higher prevalence (5.6%) compared with the high and low dietary diversity group (4.3%). Multiple logistic regression analysis revealed low dietary diversity was associated with CKD in older adults (OR 1.30, 95%CI 1.01-1.68). Stratified analysis showed that low dietary diversity was independently associated with CKD (OR 1.43, 95% CI 1.07-1.91) in older adults with hypertension, but not in adults without hypertension (OR 0.94, 95% CI 0.54-1.64).

CONCLUSIONS AND IMPLICATIONS

This cross-sectional study revealed that low dietary diversity was associated with CKD among older adults. Furthermore, low dietary diversity was associated with CKD among older adults with hypertension.

Ultra-processed food consumption and chronic kidney disease risk: a systematic review and dose-response meta-analysis

Background

High intake of ultra-processed food (UPF) has been associated with increased risk of chronic kidney disease(CKD), but the results remain inconsistent. We therefore performed this systematic review and dose–response meta-analysis of observational studies that shed light on the association between UPF consumption and the risk of CKD.

Methods

A systematic literature search of PubMed, Embase, Web of Science, Scopus and China National Knowledge Infrastructure (CNKI) databases was carried out to find the eligible articles published up to October 31, 2023. Random-effects or fixed-effects models were used to pool the relative risks(RRs) and their 95% confidence intervals (CIs).The potential sources of heterogeneity across studies were examined using the Cochran’s Q test and I-square(I2). Publication bias was examined using the visual inspection of asymmetry in funnel plots and quantified by Begg’s and Egger’s tests.

Results

Eight studies (six cohort and two cross-sectional studies) exploring the association between UPF consumption and risk of CKD, were included in the final analysis. The pooled analyses revealed that high consumption of UPF was associated with an increased risk of CKD (RR = 1.25; 95%CI: 1.09–1.42, p &lt; 0.0001). Moreover, a 10% increase of UPF consumption was associated with a 7% higher risk of CKD (RR = 1.07; 95%CI: 1.04–1.10, p &lt; 0.001). Dose–response analysis of all included studies showed a linear association between UPF consumption and the risk of CKD (RR = 1.02; 95%CI:0.99–1.05, Pdose–response = 0.178, Pnonlinearity = 0.843).

Conclusion

Our findings indicate that high consumption of UPF is significantly associated with an increased risk of CKD. Future research with prospective design is required to confirm this positive association.

Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023478483, PROSPERO identifier CRD42023478483.

Analysis on fluid intake and urination behaviors among the elderly in five cities in China: a cross-sectional study

Background

Fluid intake in the elderly may influence urination behaviors and further influence their health status. This study investigated the behaviors of fluid intake, urination and their relationships among the elderly in China.

Methods

Stratified random sampling was used to recruit the elderly participants who met the inclusion criteria from five cities in China. Participants' total fluid intake (TFI) level was investigated using a validated 7-day 24 h fluid intake questionnaire. Their urination behaviors in real time were also recorded using a validated 7-day 24 h urination behavior record.

Results

A total of 524 participants completed the study, including 233 males and 291 females. The average age was 69.7 years. The median daily TFI was 1,241 mL, with a frequency of 8.1 times per day. Approximately 73.3% of the participants did not reach the amount of adequate fluid intake (1.7 L for males and 1.5 L for females) recommended in China. Fluid intake in the morning, afternoon, and evening among participants was 594 mL, 305 mL and 342 mL, with a frequency of 3.0 times, 1.7 times, and 2.0 times, respectively. The median urination frequency was 7.4 times per day. The percentage of participants who urinated >7 times during the day was 44.3%. The percentage of participants who urinated ≥1 time at night was 77.5%. Age and BMI were not the main influence factors for fluid intake and urination behaviors. The preliminary analysis showed that higher TFI, plain water intake, dairy products intake, and fluid intake frequency were significantly associated with higher urination frequency (t = 6.553, p < 0.05; t = 5.291, p < 0.05; t = 4.667, p < 0.05; t = 13.413, p < 0.05). Higher fluid intake per time was significantly associated with lower urination frequency (t = -3.562, p < 0.05). Correlations between TFI, fluid intake frequency, fluid intake in night, fluid intake frequency in night and urination at night were also found (r = 0.114, p < 0.05; r = 0.091, p < 0.05; r = 0.146, p < 0.05; r = 0.331, p < 0.05).

Conclusion

Fluid intake was inadequate in terms of the elderly participants. Participants with higher fluid intake and frequency in night had a greater incidence of nocturia. Thus, correcting fluid intake behaviors can improve urination behavior and promote health.

Clinical trial registration

https://www.chictr.org.cn/searchprojEN.html, identifier CTR1900023355.

Validation of Total Water Intake from the Automated Self-Administered 24-h Recall, 4-d Food Records, and a Food Frequency Questionnaire Using Doubly Labeled Water

BACKGROUND

Although prior evidence indicates that water intake is important for health, the ability to accurately measure community-dwelling intake is limited. Only a few studies have evaluated self-reported water intake against an objective recovery biomarker.

OBJECTIVES

The aim was to compare preformed water intakes (all sources including food) by multiple Automated Self-Administered 24-h recalls (ASA24s), food frequency questionnaires (FFQs), and 4-d food records (4DFRs) against a recovery biomarker, doubly labeled water (DLW), to assess measurement error.

METHODS

Over 1 y, 1082 women and men (50%), aged 50 to 74 y, were asked to complete 6 ASA24s, 2 FFQs, 2 unweighted 4DFRs, and an administration of DLW (n = 686). Geometric means of water intake by self-report tools were compared with DLW. Attenuation factors and correlation coefficients between self-reported and the recovery biomarker (DLW) were estimated.

RESULTS

Mean water intakes by DLW were 2777 mL/d (interquartile range, 2350 to 3331) in women and 3243 mL/d (interquartile range, 2720 to 3838) in men. Compared with DLW, water intake was underestimated by 18% to 31% on ASA24s and 43% to 44% on 4DFRs. Estimated geometric means from FFQs differed from DLW by -1% to +13%. For a single ASA24, FFQ, and 4DFR, attenuation factors were 0.28, 0.27, and 0.32 and correlation coefficients were 0.46, 0.48, and 0.49, respectively. Repeated use of 6 ASA24s, 2 FFQs, and 2 4DFRs improved attenuation factors to 0.43, 0.32, and 0.39 and correlation coefficients to 0.58, 0.53, and 0.54, respectively.

CONCLUSIONS

FFQs may better estimate population means for usual water intake compared with ASA24 and 4DFR. Similar attenuation factors and correlation coefficients across all self-report tools indicate that researchers have 3 feasible options if the goal is understanding intake-disease relationships. The findings are useful for planning future nutrition studies that set policy priorities for populations and to understand the health impact of water. This trial was registered at clinicaltrials.gov as NCT03268577.

Copeptin is associated with microalbuminuria and renal function in the general Japanese population

An association between copeptin (precursor molecule of arginine vasopressin) and markers for renal function has been reported, but data on the Japanese population has been limited. In this study, we investigated whether elevated copeptin levels are associated with microalbuminuria and renal dysfunction in the general Japanese population. A total of 1,262 participants (842 female and 420 male) were enrolled. Multiple regression analysis was performed to assess the association of copeptin levels (logarithm) with estimated glomerular filtration rate (eGFR) and the urine albumin-to-creatinine ratio (UACR) after adjusting for age, BMI, and lifestyle variables. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression methods in which chronic kidney disease (CKD) was the dependent variable. The copeptin levels differed significantly with sex, but were not found to be related to age or the span of time from preceding meal to blood sampling. In female participants, copeptin level was negatively correlated with eGFR (beta = -0.100, p-value = 0.006) and positively correlated with UACR (beta = 0.099, p-value = 0.003). In male participants, a negative correlation (beta = -0.140, p-value = 0.008) was observed for eGFR. In both females and males, those with high copeptin levels had more than double the ORs of CKD (OR = 2.1-2.9) adjusted for CKD-related factors. The present study found elevated copeptin levels to be associated with renal function loss in the Japanese population and microalbuminuria in female. Moreover, it was evident that high copeptin levels are associated with CKD. These results suggest that copeptin could be considered a marker of renal function.

The association between dietary micronutrient patterns and odds of diabetic nephropathy: A case-control study

Uncontrolled diabetes can lead to diabetic nephropathy (DN). The aim of the study was to investigate the relationship between different dietary micronutrient patterns and risk of DN in women. This was a case-control study. One hundred and five patients had DN (defined as urinary mg of albumin per gram of creatinine ≥30 mg/g) were chosen as the case and 105 women without DN were chosen as control. Dietary intakes were assessed by a semi-quantitative food frequency questionnaire. Principal component analysis with varimax rotation was used to derive the micronutrient patterns. Patterns were divided into two groups of lower and higher than median. Logistic regression was used to discern and find the odds ratio (ORs) of DN, and its 95% confidence interval (CI) based on the micronutrient patterns in crude and adjusted model. Three patterns which were included, (1) mineral patterns such as chromium, manganese, biotin, vitamin B6, phosphorus, magnesium, selenium, copper, zinc, potassium, and iron, (2) water-soluble vitamin patterns such as vitamin B5, B2, folate, B1, B3, B12, sodium and C, and (3) fat-soluble vitamin patterns such as calcium, vitamin K, beta carotene, alpha tocopherol, alpha carotene, vitamin E, and vitamin A, were extracted. An inverse relationship was found between risk of DN and following mineral patterns and fat-soluble vitamin patterns in adjusted model (ORs = 0.51 [95% CI 0.28-0.95], p = .03) and (ORs = 0.53 [95% CI 0.29-0.98], p = .04), respectively. No relationship was seen between water-soluble vitamin patterns and risk of DN in crude and adjusted model but the significance was decreased in adjusted model. The risk of DN was 47% decreased after high adherence of fat-soluble vitamin patterns. In addition, we saw a 49% decrease of risk of DN in high adherence group of mineral patterns. The findings confirm that renal-protective dietary patterns can reduce risk of DN.

"Failing kidneys in a failing planet; CKD of unknown origin"

The 'alarm clock' for human beings in the era of climate medicine has rung. Original diseases have appeared, that could not be explained and attributed to common causes, which are suggested to be linked to global warming and environmental factors. Such an indolent disease is the chronic kidney disease of unknown cause (CKDu), introduced also as Mesoamerican or Uddanam nephropathy. Scientists equate the climate impact on kidneys with the canary in the coal mine; coal miners used to carry caged canaries with them, so that if poisonous gases, such as methane or carbon monoxide leaked into the mine-shaft, the gases would kill the canary before killing the miners; similarly, kidneys are injured before devastating and lethal complications occur in humans. In some regions of Central America, the deaths due to chronic kidney disease increased by 177% with a death toll being as high as over 20,000. It was first documented in animals that periodic heat and dehydration have a major role in causing chronic kidney disease. Based on that observation, it is advocated that young male agricultural workers in Central America and South Asia, develop renal disease by getting exposed to extreme heat repeatedly. The clinico-pathological characteristics of this type of kidney injury, do not belong to an existing classification, even though a form of tubulo-interstitial renal disease has been proposed. In this review, we will discuss about CKDu, its epidemiology and pathophysiological mechanisms, clinical presentation and diagnostic biomarkers and examine potential therapeutic options.

Personalized prediction of optimal water intake in adult population by blended use of machine learning and clinical data

Growing evidence suggests that sustained concentrated urine contributes to chronic metabolic and kidney diseases. Recent results indicate that a daily urinary concentration of 500 mOsm/kg reflects optimal hydration. This study aims at providing personalized advice for daily water intake considering personal intrinsic (age, sex, height, weight) and extrinsic (food and fluid intakes) characteristics to achieve a target urine osmolality (U_Osm) of 500 mOsm/kg using machine learning and optimization algorithms. Data from clinical trials on hydration (four randomized and three non-randomized trials) were analyzed. Several machine learning methods were tested to predict U_Osm. The predictive performance of the developed algorithm was evaluated against current dietary guidelines. Features linked to urine production and fluid consumption were listed among the most important features with relative importance values ranging from 0.10 to 0.95. XGBoost appeared the most performing approach (Mean Absolute Error (MAE) = 124.99) to predict U_Osm. The developed algorithm exhibited the highest overall correct classification rate (85.5%) versus that of dietary guidelines (77.8%). This machine learning application provides personalized advice for daily water intake to achieve optimal hydration and may be considered as a primary prevention tool to counteract the increased incidence of chronic metabolic and kidney diseases.

Water - A life-giving toxin - A nephrological oxymoron. Health consequences of water and sodium balance disorders. A review article

BACKGROUND

This article aims to reveal misconceptions about methods of assessment of hydration status and impact of the water disorders on the progression of kidney disease or renal dysfunction.

MATERIALS AND METHODS

The PubMed database was searched for reviews, meta-analyses and original articles on hydration, volume depletion, fluid overload and diagnostic methods of hydration status, which were published in English.

RESULTS

Based on the results of available literature the relationship between the amount of fluid consumed, and the rate of progression of chronic kidney disease, autosomal dominant polycystic kidney disease, and kidney stones disease was discussed. Selected aspects of the assessment of the hydration level in clinical practice based on physical examination, laboratory tests, and imaging are presented. The subject of in-hospital fluid therapy is discussed. Based on available randomized studies, an attempt was made to assess, which fluids should be selected for intravenous treatment.

CONCLUSIONS

There is some evidence for the beneficial effect of increased water intake in preventing recurrent cystitis and kidney stones, but there are still no convincing data for chronic kidney disease and autosomal dominant polycystic kidney disease. Further studies are needed to clarify the aforementioned issues and establish a reliable way to assess the volemia and perform suitable fluid therapy.

Quality of Beverage Intake and Cardiometabolic and Kidney Outcomes: Insights From the STANISLAS Cohort

Background and Aims: Beverages are an important aspect of diet, and their quality can possibly affect health. The Healthy Beverage Index (HBI) has been developed to take into account these effects. This study aimed to highlight the relationships between health and beverage quality by assessing the association of the HBI and its components with kidney and cardiometabolic (CM) outcomes in an initially healthy population-based familial cohort.

Methods: This study included 1,271 participants from the STANISLAS cohort. The HBI, which includes 10 components of habitual beverage consumption, was calculated. Associations of the HBI and its components with estimated glomerular filtration rate (eGFR), albuminuria, hypertriglyceridemic waist (HTG waist), metabolic syndrome (MetS), carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (cIMT), and left ventricular mass (LV mass) were analyzed using multivariable linear or logistic regression models.

Results: The median HBI score was 89.7 (78.6–95) out of 100 points. While the overall HBI score was not significantly associated with any of the studied outcomes, individual HBI components were found differently associated with the outcomes. cfPWV and cIMT were lower in participants who did not meet the full-fat milk criteria (p = 0.03 and 0.001, respectively). In men, higher cfPWV was observed for the “low Fat milk” (p = 0.06) and “alcohol” (p = 0.03) non-adherence criteria. Odds of HTG waist were higher with the non-adherence to sugar-sweetened beverages criteria (p < 0.001). eGFR was marginally higher with non-adherence to the coffee/tea criteria (p = 0.047).

Conclusions: In this initially healthy population, HBI components were differently associated with kidney and cardiometabolic outcomes, despite a good overall HBI score. Our results highlight specific impacts of different beverage types and suggest that beverages could have an impact on kidney and cardiometabolic health.

Benefits of water intake on kidney function in older adults: protocol for a randomized controlled trial

Objective: The goal of this study is to evaluate the benefits of an increase in water intake guided by a mathematical formula (per kg of body weight) on kidney function in older adults. Methods: Older adults (≥ 65 years old) cared for at the Internal Medicine Unit of a tertiary hospital will be randomized to receive or not guidance on water intake (30 mL/kg per day) after initial assessment of kidney function. After 14 days, participants will be reevaluated through clinical and laboratory examinations. Patients with uncompensated disease will be excluded. The main outcomes will be glomerular filtration rate and laboratory measures such as serum and urinary osmolality, sodium, urea, 24-h urine volume and serum creatinine, uric acid, and copeptin. The Mini Nutritional Assessment (MNA) questionnaire will be applied to participants at each visit. Categorical variables will be described as numbers of cases (%) and compared using the χ2 test whereas continuous variables will be analyzed with Student’s t-test in relation to baseline measures. The Generalized Estimating Equations (GEE) method will be performed to assess differences over time and between groups. This study was approved by the Institution’s Research Ethics Committee (grant number 16-0153) and is in accordance with the Declaration of Helsinki. Expected Results:By increasing water intake (ml/Kg) we expect to provide an improvement in kidney function in older population assessed by serum creatinine and cystatin-c applied to eGFR formulas. Relevance:Many conditions, both organic and behavioral, can contribute to chronic dehydration states in older adults. To mention, decreased ability to concentrate urine, reduced kidney mass, blood flow, and glomerular filtration rate (GFR) along with changes in sensitivity to hormones such as renin, vasopressin and natriuretic peptide can generate water imbalance, leading to dehydration. For being simple and inexpensive, this strategy may be broadly used and bring several health benefits to older adults.

Association between Frequency of Consumption of Pork Se’i and Chronic Kidney Disease in East Nusa Tenggara, Indonesia

BACKGROUND: As a country with various cultures, Indonesia has several regional specialties, one of which is Pork Se’i from East Nusa Tenggara. Studies showed that higher intake of red and processed meat was significantly associated with an increased risk for incident chronic kidney disease (CKD). AIM: This study was conducted with the goal to find out the relationship between consumption of Pork Se’i and water intake with CKD among patient in RSUD W.Z. Johannes, Kupang, East Nusa Tenggara, Indonesia. METHODS: This research was an observational study with a case–control design involving 92 respondents at W.Z Hospital Johannes in the period of July 2020. The determination of consumption of Pork Se’i and water was acquired through the use of Semi Quantitative Food Frequency Questionnaire as an instrument. Chi-square test was used as a statistical test for this study. RESULTS: In the case group, more than half of the respondents (58.7%) were male, while in the control group, more than half of the respondents (60.9%) were female. More than half (58.7%) of case group respondents consume water <1 L/day. More than half (58.7%) of case group respondents consume water <1 L/day, while most of the control group respondents (73.9%) consumed 1 L of water/day. The Pearson Chi-square test showed significant relationship between water consumption and CKD (p = 0.003). The frequency of consumption of Pork Se’i in the case group respondents was mostly in the sometimes (47.8%) and usually (47.8%) categories. Only a small proportion of case respondents (4.3%) rarely consume Pork Se’i. There was a significant relationship between consumption of Pork Se’i with CKD (p = 0.014). CONCLUSIONS: Our study found that consumption of Pork Se’i has a significant correlation with CKD.

The dietary intake of chronic kidney disease according to stages: Findings from the Korean National Health and Nutritional Examination Survey

Appropriate dietary adjustment in patients with chronic kidney disease (CKD) is important, and nutritional guidelines recommend different dietary management depending on the CKD stage. However, there is no study, to our knowledge, of the characteristics of dietary intake according to CKD stages. We tried to assess the comparison of nutritional intake according to CKD stages. A cross-sectional study was conducted to reveal the characteristics of dietary intake among patients with CKD based on the Korean National Health and Nutritional Examination Survey between 2011 and 2014. Of 16,878 participants, we classified non-CKD (n = 14,952) and CKD (n = 1,926), which was stratified into five groups (I, II, IIIa, IIIb, and IV–V). We investigated the characteristics of dietary intake, such as energy, water, protein, fat, carbohydrate, sodium, potassium, calcium, and phosphorus, according to stage of CKD. We also explored nutritional intake according to CKD stage among patients with early CKD (stage I and II) and advanced CKD (stage IIIa, IIIb, and IV–V). Intake of majority of nutrients and energy tended to be decreased as CKD progressed. In early CKD stage, intake of energy, water, protein, fat, carbohydrate, potassium, calcium and phosphorus seemed to be statistically significant decreased as CKD progressed. In advanced CKD stage, intake of potassium and calcium seemed to be decreased as CKD progressed, but the intake of energy was about to be lower limit. Appropriate dietary education and CKD recognition are needed to improve nutritional intake depending on the CKD stage.

The Road to Healthy Ageing: What Has Indonesia Achieved So Far?

The World Health Organization (WHO) has projected that the world should prepare for an aging society. As the fourth most populous country in the world, the elderly population in Indonesia is also continuously growing. In 2010, the proportion of the elderly group was merely 5%, and it is expected to increase to 11% in 2035. Understanding the current situation of the adult population in Indonesia would be crucial to prepare for the future aging population. This article analyzed the current socio-demographic status, nutrition status, nutrient intake, and health profile of the current Indonesian adult population through a literature review. The key issues to prepare for healthy aging in Indonesia are summarized. Acknowledging the profile of the adult and senior adult population in Indonesia will provide beneficial information for all stakeholders in preparing Indonesia for a better healthy aging population with improved quality of life.

Higher volume of water intake is associated with lower risk of albuminuria and chronic kidney disease

Increased water intake correlated to lower vasopressin level and may benefit kidney function. However, results of previous studies were conflicted and inconclusive. We aimed to investigate the association between water intake and risk of chronic kidney disease (CKD) and albuminuria.In this cross-sectional study, the study population were adult participants of 2011-2012 National Health and Nutrition Examination Survey (NHANES) whose estimated glomerular filtration rate (eGFR) were ≥30 ml/min/1.73 m2. Data of water intake were obtained from the NHANES 24-h dietary recall questionnaire. Participants were divided into three groups based on volume of water intake: <500 (low, n = 1589), ≥500 to <1200 (moderate, n = 1359), and ≥1200 ml/day (high, n = 1685). CKD was defined as eGFR <60 ml/min/1.73 m2, and albuminuria as albumin-to-creatinine ratio (ACR) ≥30 mg/g.Our results showed that 377 out of 4633 participants had CKD; the prevalence inversely correlated to volume of water intake: 10.7% in low, 8.2% in moderate, and 5.6% in high intake groups (P < .001). Prevalence of albuminuria was also lower in high (9.5%) compared with moderate (12.8%) and low intake groups (14.1%), P < .001. Additionally, water intake positively correlated to eGFR and negatively correlated to urinary ACR, as well as plasma and urine osmolality. Multivariable logistic regression showed that low water intake group had higher risk of CKD (OR 1.35, 95% CI 1.01-1.82) and albuminuria when compared to high water intake group (OR 1.42, 95% CI 1.13-1.79).In conclusion, increased water intake was associated lower risk of CKD and albuminuria. Meticulous studies are needed to elucidate the underlying mechanisms.

Dietary patterns associated with renal impairment in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA)

Background

Dietary-based primary prevention guidelines for chronic kidney disease (CKD) treatment are lacking due to limited evidence. Single nutrient intake studies do not account for complex dietary interactions. We assessed associations between dietary patterns and renal function in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA).

Design

A cross-sectional observational study used NICOLA baseline dietary data collected between February 2014 and March 2016 via a food frequency questionnaire for 2590 participants aged ≥ 50 years. Principal component analysis identified a posteriori dietary patterns. Renal function was characterised by estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin-C. Associations were assessed according to quintiles of dietary pattern adherence and multivariable regression analysis examined associations with eGFR.

Results

Variation in three dietary patterns was significantly associated with eGFR. After adjustment for potential confounders, participants with least adherence to the ‘healthy’ dietary pattern 1 had a mean eGFR 3.4 ml/min/1.73m² (95% confidence interval, [CI] − 5.0, − 1.7, p < 0.001) lower than the most adherent. Those with lowest adherence to the ‘unhealthy’ dietary pattern 2 had a mean eGFR 1.9 ml/min/1.73m² (CI 0.2, 3.5, p = 0.03) higher than those with highest adherence. Participants with lowest adherence to dietary pattern 3, characterised by a high consumption of alcohol and coffee, had a mean eGFR 1.8 ml/min/1.73m² (− 3.5, − 0.01, p = 0.05) lower than those with greatest adherence.

Conclusions

Our findings identify independent associations between dietary patterns and eGFR. These findings can inform the development of diet-related primary prevention advice for CKD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02579-z.

A Subset of Primary Polydipsia, "Dipsogneic Diabetes Insipidus", in Apparently Healthy People Due to Excessive Water Intake: Not Enough Light to Illuminate the Dark Tunnel

Dipsogenic diabetes insipidus (DDI) is a subtype of primary polydipsia (PP), which occurs mostly in healthy people without psychiatric disease. In contrast, PP is characterized by a polyuria polydipsia syndrome (PPS) associated with psychiatric illness. However, the pathogenesis of DDI is not well established and remains unexplored. In order to diagnose DDI, the patient should exhibit excessive thirst as the main symptom, in addition to no history of psychiatric illness, polyuria with low urine osmolality, and intact urine concentrating ability. Treatment options for DDI remain scarce. On this front, there have been two published case reports with successful attempts at treating DDI patients. The noteworthy commonalities in these reports are that the patient was diagnosed with frequent excessive intake of water due to a belief that drinking excess water would have pathologic benefits. It could therefore be hypothesized that the increasing trend of excessive fluid intake in people who are health conscious could also contribute to DDI. Hence, this review provides an overview of the pathophysiology, diagnosis, and treatment, with a special emphasis on habitual polydipsia and DDI.

Impact of water consumption on renal function in the general population: a cross-sectional analysis of KNHANES data (2008-2017)

BACKGROUND

The renoprotective effect of water intake remains unclear. We aimed to investigate the relationship between water intake and renal impairment in the Korean general population, focusing on individual differences in body fluid distribution and risk of chronic dehydration.

METHODS

We conducted a cross-sectional analysis of the 2008-2017 Korea National Health and Nutrition Examination Survey (KNHANES). Adult participants who had body weight and serum creatinine data and had answered 24-h recall nutritional survey were included. Four water intake groups were defined by daily total water intake per body weight: lowest (< 20 mL/kg/day), low-moderate (20-29.9 mL/kg/day), high-moderate (30-49.9 mL/kg/day), and highest (≥ 50 mL/kg/day). We assessed the risk of renal impairment (estimated glomerular filtration rate ≤ 60 mL/min/1.73 m2) according to water intake.

RESULTS

In total of 50,113 participants, 3.9% had renal impairment. The risk of renal impairment gradually decreased as water intake increased. After adjustment of sodium intake, the trend of renoprotective effect was remained in low-moderate and high-moderate water intake group compared to low intake group, whereas no significant impact was observed with the highest water intake due to concurrent intake of high sodium. In subgroup analysis, the renoprotective effect of water intake was significant in the participants with elderly, male and daily sodium intake over 2 g/day.

CONCLUSIONS

High daily water intake is renoprotective. Our data may provide an important basis for determining the amount of water intake needed to prevent renal impairment, considering variations in body weight, body composition and risk of chronic dehydration.

Understanding Attitudes to Change to Healthier Hydration Habits: The Case of High Sugar: Low Water Drinkers in Mexico

Adults consuming sugar-sweetened beverages (SSBs) are at increased risk of becoming overweight/obese and developing lifestyle-related diseases. Furthermore, a low water intake is associated with increased health risks, such as CKD. These issues are especially pressing in Mexico where SSB intake is high. The present research aimed to describe the attitudes of Mexican adults who are considered high sugar-low water drinkers (HS-LWDs). HS-LWDs were defined as adults aged 18-45 years, drinking at least 2 servings (500 mL) of SSB/day and maximum 3 servings (750 mL) of water/day. The study included 2.858 HS-LWD (58% males) living in the urban area of Mexico City. Data were collected using an online, self-administered questionnaire. Bayesian approach was applied to analyze attitudes in life and towards drinking. Results showed that social aspects, such as sharing with friends and family and self-image, were the dominant attitudes in life. The main reason to choose a beverage was to get sensations, resulting in 2 axes, one was pleasure oriented and one was health oriented. Getting sensations was also a main driver to drink linked to a moment, together with self-image. The Bayesian network analysis demonstrated 5 attitude profiles, based on the most important attitudes defining each profile: mood and pleasure, self-image and body image, sharing and restoring, pleasure and energy, and health and success. This study allowed describing HS-LWD attitudes, in life and towards drinking. It constitutes a first step in understanding this target group's attitudes and behavior, offering potential recommendations for tailored interventions to promote the adoption of healthier drinking habits.

Water intake and progression of chronic kidney disease: the CKD-REIN cohort study

Background

Optimal daily water intake to prevent chronic kidney disease (CKD) progression is unknown. Taking the kidney’s urine-concentrating ability into account, we studied the relation of kidney outcomes in patients with CKD to total and plain water intake and urine volume.

Methods

Including 1265 CKD patients [median age 69 years; mean estimated glomerular filtration rate (eGFR) 32 mL/min/1.73 m2] from the Chronic Kidney Disease–Renal Epidemiology and Information Network cohort (2013–19), we assessed fluid intake at baseline interviews, collected 24-h urine volumes and estimated urine osmolarity (eUosm). Using Cox and then linear mixed models, we estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for kidney failure and eGFR decline associated with hydration markers, adjusting for CKD progression risk factors and eUosm.

Results

Patients’ median daily intake was 2.0 L [interquartile range (IQR) 1.6–2.6] for total water and 1.5 L (1–1.7) for plain water, median urine volume was 1.9 L/24 h (IQR 1.6–2.4) and mean eUosm was 374 ± 104 mosm/L. Neither total water intake nor urine volume was associated with either kidney outcome. Kidney failure risk increased significantly with decreasing eUosm ˂292 mosm/L. Adjusted HRs (95% CIs) for kidney failure associated with plain water intake were 1.88 (1.02–3.47), 1.59 (1.06–2.38), 1.76 (0.95–3.24) and 1.55 (1.03–2.32) in patients drinking &lt;0.5, 0.5–1.0, 1.5–2.0 and &gt;2.0 L/day compared with those drinking 1.0–1.5  L/day. High plain water intake was also significantly associated with faster eGFR decline.

Conclusions

In patients with CKD, the relation between plain water intake and progression to kidney failure appears to be U-shaped. Both low and high intake may not be beneficial in CKD.

Dietary patterns and chronic kidney disease risk: a systematic review and updated meta-analysis of observational studies

BACKGROUND

A number of studies have reported the association between dietary patterns and the risk of chronic kidney disease (CKD), however a consistent perspective hasn't been established to date. Herein, we conducted this systematic review and meta-analysis of observational studies to assess the association between dietary patterns and CKD.

METHODS

MEDLINE, EBSCO and references from eligible studies were searched for relevant articles published up to 9 May 2020 that examined the association of common dietary patterns and CKD. The heterogeneity among studies was assessed by Cochran's Q test and I² methods.

RESULTS

Seventeen eligible studies, involving 149,958 participants, were included in our systematic review and meta-analysis. The highest compared with the lowest category of healthy dietary pattern was significantly associated with a lower risk of CKD (OR=0.69; CI: 0.57, 0.84; P=0.0001). A higher risk of CKD was shown for the highest compared with the lowest categories of Western-type dietary pattern (OR=1.86; CI: 1.21, 2.86; P=0.005). There were evidence of a lower risk of CKD in the highest compared with the lowest categories of light-moderate drinking pattern (OR=0.76; CI: 0.71, 0.81; P< 0.0001) and heavy drinking pattern (OR=0.67; CI: 0.56, 0.80; P< 0.0001).

CONCLUSIONS

The results of this systematic review and meta-analysis show that a healthy dietary pattern and alcohol drinking were associated with lower risk of CKD, whereas a Western-type dietary pattern was associated with higher risk of CKD.

The comparison of water intake patterns and hydration biomarkers among young adults with different hydration statuses in Hebei, China

Background

Water is essential for maintaining the functions of human body properly. Studies have shown that the amounts and contributions of fluids were associated with health and hydration status. The objectives of the study was that to explore the differences of water intake pattern and hydration biomarkers among young males and females in different hydration statuses.

Methods

A cross-sectional study was implemented among 159 young adults aged 18–23 years in Hebei, China. The total drinking fluids and water from food were obtained by 7-day 24-h fluid intake questionnaire and duplicate portion method, respectively. The osmolality and electrolyte concentrations of the 24 h urine and plasma were tested. Differences in optimal hydration (OH), middle hydration (MH) and hypohydration (HH) groups, divided by the osmolality of 24 h urine, were compared.

Results

Totally, 156 participants (80 males and 76 females) completed the study. OH group had highest proportions of participants met the recommendations of total water intake (TWI) and total drinking fluids of China (34.5%, 36.2%), while HH group had lowest (7.7%, 0.0%). OH group had higher amounts of TWI, total drinking fluids, water and lower amounts of sugar-sweetened-beverages (SSBs) (P < 0.05). The percentage of total drinking fluids in TWI decreased from 54.1% in OH group to 42.6% in HH group (P < 0.05). OH group had higher and lower contributions of water and SSBs to total drinking fluids (P < 0.05); produced 551–950 mL more, excreted significantly less quantity of solutes of urine (P < 0.05). No significant differences were found in plasma osmolality among the three groups (P > 0.05). Among both males and females, the amounts of TWI and water were higher in OH group than others (P < 0.05). Males had 4.3% lower, 5.4% and 1.1% higher contributions of milk and milk products, SSBs and alcohol to total drinking fluids than females (P < 0.05); males had higher volume of urine than females only in MH group (P < 0.05). There were no significant differences of plasma osmolality between males and females in the same group (P > 0.05).

Conclusions

Young adults with optimal hydration status had better water intake pattern and less concentrated urine. Females maybe have better water intake pattern than males.

Trial registration Chinese clinical trial registry. Name of the registry: Relationship of drinking water and urination. Trial registration number: ChiCTR-ROC-17010320. Date of registration: 01/04/2017. URL of trial registry record: http://www.chictr.org.cn/edit.aspx?pid=17601&htm=4.

Association of vitamin D status with liver and kidney disease: A systematic review of clinical trials, and cross-sectional and cohort studies

Abstract. Background: Vitamin D deficiency (VDD) is a major public health problem. There are few comprehensive systematic reviews about the relationship between Vitamin D status and liver and renal disease in Iran.

Methods: We systemically searched the following databases: Web of Science; PubMed; Cochrane Library; Scopus; Science Direct; Google Scholar and two Iranian databases (Scientific Information Database (SID) and IranMedex) up until November 2017 to identify all randomized control trials (RCTs), case control, cross-sectional and cohort studies investigating the association between vitamin D and any form of liver or kidney disease.

Results: Vitamin D insufficiency, or deficiency (VDD), is highly prevalent in Iran, reports varying between 44.4% in Isfahan to 98% in Gorgan. There is also a high prevalence of VDD among patients with liver or kidney disease, and the administration of vitamin D supplements may have beneficial effects on lipid profile, blood glucose, liver function and fatty liver disease, and bone health. Low serum vitamin D levels are related with abnormalities in these laboratory and clinical parameters.

Conclusion: VDD is prevalent in patients with chronic liver or renal disease in Iran. There appear to be several beneficial effects of vitamin D supplementation in vitamin D deficient patients with liver or kidney disease.

The Role of Disturbed Mg Homeostasis in Chronic Kidney Disease Comorbidities

Some of the critical mechanisms that mediate chronic kidney disease (CKD) progression are associated with vascular calcifications, disbalance of mineral metabolism, increased oxidative and metabolic stress, inflammation, coagulation abnormalities, endothelial dysfunction, or accumulation of uremic toxins. Also, it is widely accepted that pathologies with a strong influence in CKD progression are diabetes, hypertension, and cardiovascular disease (CVD). A disbalance in magnesium (Mg) homeostasis, more specifically hypomagnesemia, is associated with the development and progression of the comorbidities mentioned above, and some mechanisms might explain why low serum Mg is associated with negative clinical outcomes such as major adverse cardiovascular and renal events. Furthermore, it is likely that hypomagnesemia causes the release of inflammatory cytokines and C-reactive protein and promotes insulin resistance. Animal models have shown that Mg supplementation reverses vascular calcifications; thus, clinicians have focused on the potential benefits that Mg supplementation may have in humans. Recent evidence suggests that Mg reduces coronary artery calcifications and facilitates peripheral vasodilation. Mg may reduce vascular calcification by direct inhibition of the Wnt/β-catenin signaling pathway. Furthermore, Mg deficiency worsens kidney injury induced by an increased tubular load of phosphate. One important consequence of excessive tubular load of phosphate is the reduction of renal tubule expression of α-Klotho in moderate CKD. Low Mg levels worsen the reduction of Klotho induced by the tubular load of phosphate. Evidence to support clinical translation is yet insufficient, and more clinical studies are required to claim enough evidence for decision-making in daily practice. Meanwhile, it seems reasonable to prevent and treat Mg deficiency. This review aims to summarize the current understanding of Mg homeostasis, the potential mechanisms that may mediate the effect of Mg deficiency on CKD progression, CVD, and mortality.

Hydration for health hypothesis: a narrative review of supporting evidence

PURPOSE

An increasing body of evidence suggests that excreting a generous volume of diluted urine is associated with short- and long-term beneficial health effects, especially for kidney and metabolic function. However, water intake and hydration remain under-investigated and optimal hydration is poorly and inconsistently defined. This review tests the hypothesis that optimal chronic water intake positively impacts various aspects of health and proposes an evidence-based definition of optimal hydration.

METHODS

Search strategy included PubMed and Google Scholar using relevant keywords for each health outcome, complemented by manual search of article reference lists and the expertise of relevant practitioners for each area studied.

RESULTS

The available literature suggest the effects of increased water intake on health may be direct, due to increased urine flow or urine dilution, or indirect, mediated by a reduction in osmotically -stimulated vasopressin (AVP). Urine flow affects the formation of kidney stones and recurrence of urinary tract infection, while increased circulating AVP is implicated in metabolic disease, chronic kidney disease, and autosomal dominant polycystic kidney disease.

CONCLUSION

In order to ensure optimal hydration, it is proposed that optimal total water intake should approach 2.5 to 3.5 L day^-1 to allow for the daily excretion of 2 to 3 L of dilute (< 500 mOsm kg^-1) urine. Simple urinary markers of hydration such as urine color or void frequency may be used to monitor and adjust intake.

Diagnostic accuracy of urinary indices to detect mild dehydration in young men following acute riboflavin, Vitamin C or beetroot supplementation

BACKGROUND

Individuals of all ages are encouraged to monitor their hydration status daily to prevent clinically severe fluid imbalances such as hyponatremia or dehydration. However, acute oral nutritional supplementation may alter urinary hydration assessments and potentially increase the likelihood of inappropriate clinical decisions or diagnosis. This investigation sought to examine the influence of three common over-the-counter nutritional supplements (beetroot, riboflavin, and Vitamin C) on urinary hydration assessments in physically active young men after a 2% exercise-induced dehydration.

DESIGN

Eight males (Mean ± SD; age: 22 ± 3 yr; body mass index: 27 ± 5.0) consumed either a standard meal with supplementation (intervention) or a standard meal without supplementation (control). Participants performed a variety of aerobic or resistance exercises until reaching ≥2% body mass loss in a counter-balanced, double-blinded design. Following exercise participation, urine samples were collected for an 8 h observational period during which food consumption was replicated. Urine samples were analyzed for urine color, specific gravity, volume, and osmolality. Maintenance of ~2% body mass loss (2.6 ± 0.5%; range: 1.7-4.0%) was confirmed following the 8 h observational period.

RESULTS

Statistically significant (p < 0.05) changes were noted in urine color following Vitamin C supplementation compared to control; however, the difference was not clinically meaningful.

CONCLUSIONS

These findings indicate that urine color, specific gravity, and osmolality maintain clinical utility to detect moderate levels of dehydration in physically active men consuming commercially available doses of beetroot, riboflavin, or Vitamin C.

Distinguishing Low and High Water Consumers-A Paradigm of Disease Risk

A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers. Investigators have learned that the TWI of LOW and HIGH differ by 1-2 L·d-1, their hematological values (e.g., plasma osmolality, plasma sodium) are similar and lie within the laboratory reference ranges of healthy adults and both groups appear to successfully maintain water-electrolyte homeostasis. However, LOW differs from HIGH in urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity), as well as higher plasma concentrations of arginine vasopressin (AVP) and cortisol. Further, evidence suggests that both a low daily TWI and/or elevated plasma AVP influence the development and progression of metabolic syndrome, diabetes, obesity, chronic kidney disease, hypertension and cardiovascular disease. Based on these studies, we propose a theory of increased disease risk in LOW that involves chronic release of fluid-electrolyte (i.e., AVP) and stress (i.e., cortisol) hormones. This narrative review describes small but important differences between LOW and HIGH, advises future investigations and provides practical dietary recommendations for LOW that are intended to decrease their risk of chronic diseases.

Instructions for kidney recipients and donors (In English for medical providers and in Arabic for patients and donors)

Medical providers are often asked by their kidney recipients and donors about what to do or to avoid. Common questions include medications, diet, isolation, return to work or school, pregnancy, fasting Ramadan, or hajj and Omrah. However, there is only scant information about these in English language and none in Arabic. Here, we present evidence-based education materials for medical providers (in English language) and for patients and donors (in Arabic language). These educational materials are prepared to be easy to print or adopt by patients, providers, and centers.

Plasma copeptin as a predictor of kidney disease

Background

Plasma copeptin, a marker of vasopressin, is associated with renal function decline in the general population. Our aim was to study the links between elevated copeptin and future risk of kidney disease.

Methods

Copeptin was measured in a sample of the Malmö Preventive Project (MPP) Reinvestigation (n = 5158) and in the Malmö Diet and Cancer Cardiovascular Cohort (MDC-CC) (n = 5162). According to national registers, 89 subjects in MPP and 180 in MDC-CC developed chronic kidney disease (CKD) during follow-up (8.7 and 19.6 years, respectively).

Results

After multivariate adjustment (gender, age, body mass index, smoking status, estimated glomerular filtration rate, prevalent diabetes, systolic blood pressure and prevalent antihypertensive treatment), copeptin (beta-coefficient per 1 standard deviation increment of ln copeptin) was independently associated with increased risk of CKD during follow-up in both cohorts (MPP: (HR) 1.46, 95% confidence interval (CI) 1.18–1.80, P < 0.001; MDC-CC: HR 1.25, 95% CI 1.02–1.54, P = 0.03) among subjects free from prevalent kidney disease at baseline. Furthermore, in MPP, elevated copeptin predicted a specified diagnosis of kidney disease other than CKD (HR 1.31, 95% CI 1.08–1.59, P = 0.006) after multivariate adjustment. In a corresponding analysis in MDC-CC, copeptin was associated with a 10% increased risk, which, however, was non-significant (P = 0.25). A meta-analysis of the MPP and MDC-CC data showed significant association between elevated copeptin and a specified diagnosis of kidney disease other than CKD (HR 1.18, 95% CI 1.05–1.34, P = 0.008).

Conclusion

An increased level of copeptin independently predicts development of both CKD and other specified kidney diseases, suggesting that copeptin can be used to identify individuals at risk for kidney disease development.

Antidiuretic Hormone and Serum Osmolarity Physiology and Related Outcomes: What Is Old, What Is New, and What Is Unknown?

CONTEXT

Although the physiology of sodium, water, and arginine vasopressin (AVP), also known as antidiuretic hormone, has long been known, accumulating data suggest that this system operates as a more complex network than previously thought.

EVIDENCE ACQUISITION

English-language basic science and clinical studies of AVP and osmolarity on the development of kidney and cardiovascular disease and overall outcomes.

EVIDENCE SYNTHESIS

Apart from osmoreceptors and hypovolemia, AVP secretion is modified by novel factors such as tongue acid-sensing taste receptor cells and brain median preoptic nucleus neurons. Moreover, pharyngeal, esophageal, and/or gastric sensors and gut microbiota modulate AVP secretion. Evidence is accumulating that increased osmolarity, AVP, copeptin, and dehydration are all associated with worse outcomes in chronic disease states such as chronic kidney disease (CKD), diabetes, and heart failure. On the basis of these pathophysiological relationships, an AVP receptor 2 blocker is now licensed for CKD related to polycystic kidney disease.

CONCLUSION

From a therapeutic perspective, fluid intake may be associated with increased AVP secretion if it is driven by loss of urine concentration capacity or with suppressed AVP if it is driven by voluntary fluid intake. In the current review, we summarize the literature on the relationship between elevated osmolarity, AVP, copeptin, and dehydration with renal and cardiovascular outcomes and underlying classical and novel pathophysiologic pathways. We also review recent unexpected and contrasting findings regarding AVP physiology in an attempt to explain and understand some of these relationships.

Afternoon urine osmolality is equivalent to 24 h for hydration assessment in healthy children

BACKGROUND/OBJECTIVES

While daily hydration is best assessed in 24-h urine sample, spot sample is often used by health care professionals and researchers due to its practicality. However, urine output is subject to circadian variation, with urine being more concentrated in the morning. It has been demonstrated that afternoon spot urine samples are most likely to provide equivalent urine concentration to 24-h urine samples in adults. The aim of the present study was to examine whether urine osmolality (UOsm) assessed from a spot urine sample in specific time-windows was equivalent to 24-h UOsm in free-living healthy children.

SUBJECTS/METHODS

Among 541 healthy children (age: 3-13 years, female: 45%, 77% non-Hispanic white, BMI:17.7 ± 4.0 kg m^-2), UOsm at specific time-windows [morning (0600-1159), early afternoon (1200-1559), late afternoon (1600-1959), evening (2000-2359), overnight (2400-0559), and first morning] was compared with UOsm from the corresponding pooled 24-h urine sample using an equivalence test.

RESULTS

Late afternoon (1600-1959) spot urine sample UOsm value was equivalent to the 24-h UOsm value in children (P < 0.05; mean difference: 62 mmol kg^-1; 95% CI: 45-78 mmol kg^-1). The overall diagnostic ability of urine osmolality assessed at late afternoon (1600-1959) to diagnose elevated urine osmolality on the 24-h sample was good for both cutoffs of 800 mmol kg^-1 [area under the curve (AUC): 87.4%; sensitivity: 72.6%; specificity: 90.5%; threshold: 814 mmol kg^-1] and 500 mmol kg^-1 (AUC: 83.5%; sensitivity: 75.0%; specificity: 80.0%; threshold: 633 mmol kg^-1).

CONCLUSION

These data suggest that in free-living healthy children, 24-h urine concentration may be approximated from a late afternoon spot urine sample. This data will have practical implication for health care professionals and researchers.

Association between dietary patterns and chronic kidney disease in a middle-aged Chinese population

OBJECTIVE

To explore the relationship between dietary patterns and risk of chronic kidney disease (CKD) in Chinese adults aged 45-59 years.

DESIGN

Dietary data were collected using a semi-quantitative FFQ. Factor analysis was used to identify the major dietary patterns. Logistic regression models were applied to clarify the association between dietary patterns and the risk of CKD.

SETTING

The present study population was a part of the population-based Nutrition and Health Study performed in the city of Hangzhou, Zhejiang Province, eastern China.

PARTICIPANTS

A total of 2437 eligible participants (45-59 years) were enrolled in the present cross-sectional study from June 2015 to December 2016.

RESULTS

Three major dietary patterns were identified: 'traditional southern Chinese', 'Western' and 'grains-vegetables' patterns, collectively accounting for 25·6 % of variance in the diet. After adjustment for potential confounders, participants in the highest quartile of the Western pattern had greater odds for CKD (OR = 1·83, 95 % CI 1·21, 2·81; P < 0·05) than those in the lowest quartile. Compared with the lowest quartile of the grains-vegetables pattern, the highest quartile had lower odds for CKD (OR = 0·84, 95 % CI 0·77, 0·93; P < 0·05). In addition, there was no significant association between the traditional southern Chinese pattern and risk of CKD (P > 0·05).

CONCLUSIONS

Our results suggest that the Western pattern is associated with an increased risk, whereas the grains-vegetables pattern is associated with a reduced risk for CKD. These findings can guide dietary interventions for the prevention of CKD in a middle-aged Chinese population.

Unexplained Variance in Hydration Study

With the collection of water-intake data, the National Health and Nutrition Examination Survey (NHANES) is becoming an increasingly popular resource for large-scale inquiry into human hydration. However, are we leveraging this resource properly? We sought to identify the opportunities and limitations inherent in hydration-related inquiry within a commonly studied database of hydration and nutrition. We also sought to critically review models published from this dataset. We reproduced two models published from the NHANES dataset, assessing the goodness of fit through conventional means (proportion of variance, R²). We also assessed model sensitivity to parameter configuration. Models published from the NHANES dataset typically yielded a very low goodness of fit R² < 0.15. A reconfiguration of variables did not substantially improve model fit, and the goodness of fit of models published from the NHANES dataset may be low. Database-driven inquiry into human hydration requires the complete reporting of model diagnostics in order to fully contextualize findings. There are several emergent opportunities to potentially increase the proportion of explained variance in the NHANES dataset, including novel biomarkers, capturing situational variables (meteorology, for example), and consensus practices for adjustment of co-variates.

Adequacy of Daily Fluid Intake Volume Can Be Identified From Urinary Frequency and Perceived Thirst in Healthy Adults

Objective: Achieving and maintaining an optimal level of hydration has significant implications for both acute and chronic health, yet many hydration assessments are not feasible for the general public. Urinary frequency (UF) is a reliable method to self-assess hydration status in healthy individuals, and thirst can provide additional sensory information on adequacy of daily fluid intake volume (DFI). However, threshold values for these indices to detect optimal hydration have not been determined. In this study, we sought to determine threshold values for 24-hour UF and perceived thirst that could accurately distinguish between optimal and suboptimal hydration states.Methods: Thirty-two healthy adults (age 22 ± 3 years, body mass index 24.9 ± 4.1 kg/m²) collected urine over 24 hours on four separate occasions, where UF was recorded as well as thirst at each void using a numbered perceptual scale. Using urine osmolality as the criterion standard, all samples were either classified as representing an optimal (≤500 mOsm·kg^-1) or suboptimal hydration status (>500 mOsm·kg^-1).Results: A 24-hour UF ≤6 was able to detect suboptimal hydration with good accuracy (area under the curve [AUC] 0.815) and a 24-hour average perceived thirst rating > 3 ("a little thirsty") could detect it with reasonable accuracy (AUC 0.725). In addition, a UF ≤4 had a considerably higher positive likelihood ratio to detect suboptimal hydration versus a UF ≤6 (9.03 versus 2.18, respectively).Conclusions: These analyses suggest that individuals with a 24-hour UF ≤6 or perceiving themselves to be, on average, "a little thirsty" throughout the day are likely to be suboptimally hydrated and thus underconsuming an adequate DFI.

Dietary Care for ADPKD Patients: Current Status and Future Directions

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic nephropathy, and tolvaptan is the only therapy available. However, tolvaptan slows but does not stop disease progression, is marred by polyuria, and most patients worldwide lack access. This and recent preclinical research findings on the glucose-dependency of cyst-lining cells have renewed interest in the dietary management of ADPKD. We now review the current dietary recommendations for ADPKD patients according to clinical guidelines, the evidence base for those, and the potential impact of preclinical studies addressing the impact of diet on ADPKD progression. The clinical efficacy of tolvaptan has put the focus on water intake and solute ingestion as modifiable factors that may impact tolvaptan tolerance and ADPKD progression. By contrast, dietary modifications suggested to ADPKD patients, such as avoiding caffeine, are not well supported and their impact is unknown. Recent studies have identified a chronic shift in energy production from mitochondrial oxidative phosphorylation to aerobic glycolysis (Warburg effect) as a contributor to cyst growth, rendering cyst cells exquisitely sensitive to glucose availability. Therefore, low calorie or ketogenic diets have delayed preclinical ADPKD progression. Additional preclinical data warn of potential negative impact of excess dietary phosphate or oxalate in ADPKD progression.

Sub-morbid dehydration-associated glomerular hyperfiltration: An emerging reality?

Background

Severe dehydration decreases renal perfusion. However, it is unclear whether sub-morbid dehydration affects kidney function similarly. Although there have been numerous animal and human studies that have suggested mild dehydration is associated with glomerular hyperfiltration, it has not been confirmed on a large-scale in the general population. Therefore, we aimed to identify the relationship between hydration status and kidney function.

Methods

We reviewed the data of 28,342 adults who participated in the Korea National Health and Nutrition Examination Surveys. Urine specific gravity unit (SGU) was the primary variable that indicated hydration status, and the estimated glomerular filtration rate (eGFR) was used as the primary outcome.

Results

Multivariate linear regression analysis showed urine SGU was positively associated with eGFR, which was J-shaped in the multivariate generalized additive model plot. In the penalized spline curve analysis, the odds ratio for high eGFR was steadily increased. Although increased urine SGU was associated with decreased blood pressure and pulse rate, it had no effect on increased fasting glucose and total cholesterol, suggesting conflicting cardio-metabolic dehydration effects.

Conclusion

Dehydration, presumably sub-morbid in an ambulatory community-dwelling general population, is associated with higher kidney function. The clinical significance of sub-morbid dehydration-associated glomerular hyperfiltration needs further investigation.

Differing Water Intake and Hydration Status in Three European Countries-A Day-to-Day Analysis

Adequate hydration is essential for maintaining health and functionality of the human body. Studies assessing both daily water intake and hydration status are lacking. This study explored data from the European Hydration Research Study (EHRS) and focused on total water intake (TWI), 24 h hydration status, and day-to-day variations in a sample of 573 healthy adults. TWI was assessed by food records and hydration status (urine osmolality and urine volume) was measured from 24 urine samples collected over seven consecutive days. On all weekdays, mean TWI was higher (p < 0.001 for all days) for the German subjects compared to the Greek and Spanish participants. In 37% of the male and 22% of the female subjects, the individual mean TWI was below the European Food Safety Authority (EFSA) recommendation, with 16% men (4% women) being below the EFSA recommendation on every testing day. Twenty-four hour urine osmolality was lower in women compared to men (595 ± 261 vs. 681 ± 237 mOsmol/kg; p < 0.001). More men (40%) showed a urine osmolality ≥800 mOsmol/kg at least on four days of the study period compared to women (26%) and more participants from Spain (46%) compared to Greece (29%) and Germany (11%). A large number of individuals showed an inadequate hydration status on several days per week, which may have a negative health and cognitive impact on daily life.

Usefulness of urinary parameters in advanced chronic kidney disease

This review discusses the diagnostic value of urinary parameters in the setting of advanced chronic kidney disease and we present the key concepts that summarise the suggestions of the manuscript.

URINARY VOLUME

The amount of fluid intake may be a non-established risk factor for CKD. For these patients, a urinary output ≥2-3 l/day is a reasonable proposal. This recommendation is not applicable to patients with cardiorenal syndrome or fluid overload risk. NA: This determination is very useful to monitor salt intake. Reducing urinary Na<120 mEq/day (≅salt intake≤5-6g) is a reasonable objective.

URINARY UREA NITROGEN (UUN)

This parameter is useful to estimate protein intake (Maroni BJ equation). A protein intake between 48-72g (0.8-0.9g/kg/day according to weight) is equivalent to UUN 7-10g/day approximately.

ACID LOAD AND POTASSIUM

Acid load reduction may be an additional strategy in the nutritional management of this population. It may be estimated indirectly from a diet survey or by measuring the elimination of UUN and K_ur. The limits of this recommendation have not been established, but we propose a cautious and prudent diet of fruit and vegetables.

PHOSPHORUS

There is a significant positive correlation between phosphorus and protein, both in dietary records and urine elimination. Based on this information, we suggest a urinary P excretion<800mg/day or<600mg/day for patients with GFR<25ml/min or<15ml/min, respectively.

CONCLUSION

Urinary parameters provide sensitive and useful knowledge for clinical practice, provide information about the dietary habits of patients and the adherence to our recommendations.

Beneficial Effect of Dietary Fiber on Hyperuricemia in Rats and Humans: A Review

Hyperuricemia is recognized as a lifestyle-related disease and the prevalence is increasing in many parts of the world. Excessive intake of purines increases serum uric acid concentration and is thought to be one factor causative of hyperuricemia. Therefore, it is thought that prevention of hyperuricemia by dietary control may be very important. This is an article of our basic research regarding the role of dietary fiber in the suppression of hyperuricemia induced by dietary purines in rats; in addition, clinical research suggesting the possibility that dietary fiber intake has a beneficial effect on the prevention or suppression of hyperuricemia in humans is discussed. Our own studies reveal that the test dietary fiber significantly suppresses the elevation of serum uric acid concentration induced by dietary RNA (12.3-46.2%), adenosine-5'-monophosphate (9.5-23.2%), adenosine (10.7-20.4%), or adenine (16.3-38.9%) and suppresses experimental hyperuricemia in rats. The mechanism is presumed to be mediated by suppression of the digestion and/or absorption of dietary purines by dietary fiber. In clinical studies, intake of dietary fiber decreases serum uric acid concentrations. Reports of recent epidemiological studies indicate that higher levels of hyperuricemia increase the prevalence of its comorbidities (e.g., chronic kidney disease, obesity, hypertension, diabetes, and cardiovascular disease) and dietary fiber intake is associated with significantly lower risk for hyperuricemia and its comorbidities. We wish to emphasize the importance of recognizing the validity of increased dietary fiber intake as a preventive or suppressive method for hyperuricemia and its comorbidities.