Carbohydrate nutrition is associated with the 5-year incidence of chronic kidney disease

Association Between Plant-based Diet and Kidney Function in Adults

OBJECTIVE

A plant-based diet has both antioxidant and anti-inflammatory properties. Therefore, it is hypothesized that adherence to a plant-based diet may have a positive effect on kidney function. The study aimed to determine the association between the plant-based diet index (PDI) and chronic kidney disease (CKD).

METHODS

This cross-sectional analysis used information from the Ravansar noncommunicable diseases cohort study, which included 9,746 participants between the ages of 35 and 65. By measuring the estimation glomerular filtration rate (eGFR) with the modification of diet in the renal disease equation, CKD was determined. Using a food frequency questionnaire, the PDI was computed based on food intake. To determine odds ratios (ORs), multivariable logistic regression models were utilized.

RESULTS

1,058 (10.86%) participants had CKD (eGFR<60 mL/min/1.73 m2), and the mean PDI was 54.22 ± 6.68. The mean eGFR in the group with a high PDI score was significantly higher than the group with a low PDI score (fourth quartile: 79.20 ± 0.36 vs. first quartile: 72.95 ± 0.31, P < .001). Adherence to a plant-based diet was more prevalent in those with a higher socioeconomic status (P < .001). After adjusting for potential confounders, the odds of CKD in the third and fourth quartiles of PDI were 25% (OR: 0.75; 95% confidence interval: 0.62-0.91) and 39% (OR: 0.61; 95% confidence interval: 0.48-0.78, P trend<.001) lower than the first quartile, respectively.

CONCLUSIONS

The findings of this study suggest that having a plant-based diet may prevent the prevalent CDK. However, further studies with a cohort design are recommended.

Association of carbohydrate intake from different sources with all-cause and cardiovascular mortality among chronic kidney disease populations: assessment of 1999-2018 National Health and Nutrition Examination Survey participation

This study analysed the data from the NHANES (1999-2018) to examine how different sources of carbohydrate intake affected the all-cause and cardiovascular mortality of 11,302 chronic kidney disease (CKD) patients. The data were adjusted for other factors using various methods. The results showed that CKD patients (stages 1-2 and 3-5) who consumed more carbohydrates from whole grains, fruits, vegetables and less carbohydrates from fruit juice or sauces had lower mortality rates. Replacing fat intake with carbohydrates from whole grains (HR = 0.86[0.78-0.95]), fruits (raw) (HR = 0.79[0.70-0.88]) and non-starchy vegetables (HR = 0.82[0.70-0.96]), but not protein intake, was linked to lower all-cause mortality. The fibre content in carbohydrates might partly account for the benefits of selected carbohydrate intake. This study provided practical recommendations for optimising the carbohydrate sources in CKD patients.

Glycemic index of a nutritional supplement designed for people with chronic kidney disease

The study was carried out to measure the glycemic index (GI) of an oral food supplement for people with CKD as well as on patients on maintenance dialysis. The study was conducted as per international protocols for testing GI, was approved by the local institutional ethics committee, and was registered with the Clinical Trial Registry of India (CTRI). This was a crossover randomized controlled study which enrolled 15 participants between the ages of 18 and 45 years. The participants were randomly allotted to one group that consumed either the reference food (27.5 g of glucose monohydrate) or 118 g of the nutritional supplement which contained 25 g of available carbohydrates. Fasting capillary blood samples as well as blood samples at different time intervals as per the GI protocol, after consumption of either the supplement or the reference food were taken from the participants. Each testing day was separated by a 3-day washout period. GI was calculated from the incremental area under the blood glucose response elicited by the nutritional supplement as a percentage of the response after the consumption of 25 g of glucose (27.5 g of glucose monohydrate) by the same participant using a standard formula. The GI of the nutritional supplement was calculated to be 10.3 ± 2.0 which is considered to be low as per international GI testing standards. The product was created to supplement the diet of people with CKD at different stages and to help prevent the progression from CKD to ESRD as well as the risk for CVD. This product was found to have a low GI which is desirable for people with CKD as well as diabetics in general who are at risk for developing CKD.

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

OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

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

RESULTS

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

CONCLUSION

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

Dietary protein score and carbohydrate quality index with the risk of chronic kidney disease: Findings from a prospective cohort study

BACKGROUND/AIM

This study aimed to examine the associations between dietary protein score and carbohydrate quality index (CQI) and the risk of chronic kidney disease (CKD) in Iranian adults.

METHODS

This population-based cohort study was performed within the Tehran Lipid and Glucose Study framework on 6,044 subjects aged ≥18 years old, who were followed up for a mean of 7.7 years. Dietary protein score and CQI were determined using a food frequency questionnaire. CKD was defined as an estimated glomerular filtration rate <60 ml/min/1.73 m2. A multivariate Cox proportional hazard regression model was used to estimate the risk of CKD across tertiles of protein score and CQI.

RESULTS

The mean (standard deviation) of age and body mass index of participants were 37.9 (12.8) years and 26.8 (4.7) kg/m2, respectively. During the 7.7 ± 2.7 years of follow-up, 1,216 cases (20.1%) of CKD were ascertained. In the final adjusted model, individuals in the highest tertile of protein score had decreased risk of CKD (HR: 0.85, 95% CI: 0.74-0.98, P trend = 0.033). Also, there is a significant association between total carbohydrate score (HR: 0.85, 95% CI: 0.73-0.99, P trend = 0.016), the ratio of whole grain/total grains (HR: 0.81, 95% CI: 0.70-0.94, P trend = 0.004), and glycemic index (HR: 1.30, 95% CI: 1.12-1.51, P trend < 0.001) and risk of CKD. However, no significant association was found between total protein intakes, plant-to-animal ratio, and solid carbohydrate/total carbohydrate with the risk of CKD.

CONCLUSION

Our results revealed a diet with a high protein score and high quality of carbohydrates, characterized by higher intakes of plant proteins, low glycaemic index (GI) carbohydrates, whole grain, fibers, and lower intakes of animal proteins, can be related to reduced CKD risk.

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

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

Association Between Dietary Fiber Intake and All-Cause and Cardiovascular Mortality in Middle Aged and Elderly Adults With Chronic Kidney Disease

Background and Aims

Despite accumulating evidence on the benefits of dietary fiber in the general population, there is a lack of representative data on mortality in patients with chronic kidney disease (CKD). This study examined the role of dietary fiber intake on all-cause and cardiovascular mortality in patients with CKD using representative Korean cohort data.

Methods

The study included 3,892 participants with estimated glomerular filtration rates &lt;60 mL/min/1.73 m2 from the Korean Genome and Epidemiology Study. Mortality status was followed by data linkage with national data sources. Nutritional status was assessed using a validated food frequency questionnaire. Dietary fiber was categorized into quintiles (Q). A multivariable Cox proportional hazards regression model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and cardiovascular mortality.

Results

The average daily fiber intake of patients with CKD was 5.1 g/day. During the 10.1-year follow-up period, 602 (149 cardiovascular) deaths were documented. The HR (95% CI) for all-cause mortality in the highest quintile compared with that in the lowest quintile was 0.63 (0.46–0.87) after adjusting for age, sex, BMI, smoking, alcohol intake, exercise, total calorie intake, hypertension, diabetes, and dyslipidemia (P = 0.005). The HR (95% CI) for cardiovascular mortality in the highest quintile compared with that in the lowest quintile was 0.56 (0.29–1.08) after adjusting for same confounders (P = 0.082).

Conclusion

In conclusion, we observed an inverse association between dietary fiber intake and all-cause mortality in CKD patients. Small increments in fiber intake reduced the risk of all-cause mortality by 37%. This finding highlights the need for inexpensive but important dietary modification strategies for encouraging fiber intake in the Korean CKD population.

Fiber intake and health in people with chronic kidney disease

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

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

•

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

•

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

•

Lower protein intake decreased kidney mass and glomerular filtration capacity

•

Kidney outcomes did not align with longevity or cardiometabolic outcomes

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

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

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25%-35% of phosphorus, 12%-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25-35% of phosphorus, 12-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

Dietary Patterns and Progression of Impaired Kidney Function in Japanese Adults: A Longitudinal Analysis for the Fukushima Health Management Survey, 2011-2015

To investigate associations between dietary patterns and the risk of impaired kidney function, we analyzed data from 14,732 participants (40–89 years) who completed the baseline diet questionnaire of The Fukushima Health Management Survey in 2011. The incidence of chronic kidney disease (CKD) (estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or proteinuria (≥1+ by dipstick test)) and annual changes in eGFR were assessed from 2012 to 2015. Three major dietary patterns were identified. The adjusted cumulative incidence ratio of the highest vs. lowest tertile of a vegetable diet scores was 0.90 (95% confidence interval (CI): 0.82, 1.00) for eGFR < 60 mL/min/1.73 m², 0.68 (95% CI: 0.52, 0.90) for proteinuria, and 0.88 (95% CI: 0.80, 0.97) for CKD (P for trend = 0.031, 0.007, and 0.005, respectively). The incident risk of CKD in the highest tertile of juice diet scores was 18% higher than the lowest tertile. The odds ratio of the highest vs. lowest tertile of vegetable diet scores was 0.85 (95% CI: 0.75, 0.98) in the rapidly decreasing eGFR group (P for trend = 0.009). We did not observe significant associations for the meat dietary pattern. A Japanese vegetable diet could reduce the risk of developing impaired kidney function and CKD.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Carbohydrate-Rich Diet Is Associated with Increased Risk of Incident Chronic Kidney Disease in Non-Diabetic Subjects

Despite the potential relationship with metabolic derangements, the association between dietary carbohydrate intake and renal function remains unknown. The present study investigated the impact of dietary carbohydrate intake on the development of incident chronic kidney disease (CKD) in a large-scale prospective cohort with normal renal function. A total of 6746 and 1058 subjects without and with diabetes mellitus (DM) were analyzed, respectively. Carbohydrate intake was assessed by a 24-h dietary recall food frequency questionnaire. The primary endpoint was CKD development, defined as a composite of estimated glomerular filtration rate (eGFR) of ≤60 mL/min/1.73 m2 and the development of proteinuria. CKD newly developed in 20.1% and 36.0% of subjects during median follow-ups of 140 and 119 months in the non-DM and DM subjects, respectively. Categorization of non-DM subjects into dietary carbohydrate density quartiles revealed a significantly higher risk of CKD development in the third and fourth quartiles than in the first quartile (P = 0.037 for first vs. third; P = 0.001 for first vs. fourth). A significant risk elevation was also found with increased carbohydrate density when carbohydrate density was treated as a continuous variable (P = 0.008). However, there was no significant difference in the incident CKD risk among those with DM according to dietary carbohydrate density quartiles. Carbohydrate-rich diets may increase the risk of CKD development in non-DM subjects.

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.

Greater aortic stiffness is associated with renal dysfunction in participants of the ELSA-Brasil cohort with and without hypertension and diabetes

Background

Arterial stiffness has been associated with renal dysfunction and its progression, but the pathophysiological relation underlying this association has not been fully established, particularly among individuals without hypertension and diabetes. We investigated the cross-sectional associations between arterial stiffness and renal function in adults without cardiovascular disease, and whether this association remained among subjects without hypertension and diabetes.

Methods

All eligible participants from ELSA-Brasil (2008–2010), aged 35 to 74 years (N = 13,586) were included, of whom 7,979 were free from hypertension and diabetes. The response variables were: 1) low glomerular filtration rate (eGFR<60ml/min/1.73m²) estimated by CKD-EPI; 2) increased albumin/creatinine ratio (ACR ≥30mg/g); and 3) chronic kidney disease (CKD). Arterial stiffness was ascertained by the carotid-femoral pulse wave velocity (PWV). The covariates were sex, age, race/color, level of schooling, smoking, body mass index, total cholesterol/HDL-c glycated hemoglobin, diabetes, systolic blood pressure, heart rate and use of antihypertensive drugs. Logistic regression was used to examine the associations.

Results

After all adjustments, 1 m/s increase in PWV was associated with ORs equal to 1.10 (95%CI: 1.04–1.16), 1.10 (95%CI: 1.05–1.16) and 1.12 (95%CI: 1.08–1.17) of low eGFR, high ACR, and CKD, respectively. In subjects without hypertension and diabetes, these ORs were 1.19 (95%CI: 1.07–1.33), 1.20 (95%CI: 1.07–1.32) and 1.21 (95%CI: 1.11–1.30), respectively.

Conclusion

The increase in PWV was associated with all renal dysfunction markers, even in individuals without hypertension and diabetes, suggesting a relation that is not completely mediated by the presence of these conditions.

Carbohydrate nutrition variables and risk of disability in instrumental activities of daily living

PURPOSE

We aimed to examine the prospective association between dietary glycemic index (GI) and glycemic load (GL) of foods consumed, intakes of carbohydrates and fiber, and the ability to perform activities of daily living (ADL) in older adults.

METHODS

A total of 844 participants from the Blue Mountains Eye Study aged 60 years or older were examined from 2002-2004 to 2007-2009. Dietary information was collected using a validated, semi-quantitative food-frequency questionnaire. The Older Americans Resources and Services activities of daily living scale were administered to assess the functional status of participants. Multivariable logistic regression analysis was performed.

RESULTS

After multivariable adjustment, participants who were in the second and third quartiles of energy-adjusted total fiber intake compared to those in the first quartile of intake (reference group) at baseline had reduced risk of incident impaired instrumental activities of daily living (IADL) 5 years later: OR, 0.39 (95% CI 0.22-0.70) and OR 0.54 (95% CI 0.30-0.95), respectively. Analyses that involved dichotomized total fiber intake showed that participants in the upper three quartiles of total fiber intake (> 19 g/day), compared to those in the lowest quartile of intake (≤ 19 g/day) or reference group, had reduced IADL disability risk 5 years later: OR 0.49 (95% CI 0.31-0.79). Non-significant associations were observed with total carbohydrates, GI, and GL and with risk of impaired total and basic ADL at 5-year follow-up.

CONCLUSIONS

Habitual fiber consumption might be beneficial in leading to improved health status subserving performance of instrumental daily activities, needed to function in the community.

Dietary fibre intake in relation to the risk of incident chronic kidney disease

The purpose of this study was primarily to evaluate the association of total fibre intake with the risk of incident chronic kidney disease (CKD). We also evaluated the association of dietary fibre from fruits, vegetables, cereals and legumes with the incidence of CKD in a population-based prospective study. We followed up 1630 participants of the Tehran Lipid and Glucose Study for 6·1 years, who were initially free of CKD. Baseline diet was assessed by a valid and reliable FFQ. Estimated glomerular filtration rate (eGFR) was calculated, using the Modification of Diet in Renal Disease Study equation, and CKD was defined as eGFR <60 ml/min per 1·73 m2. OR using multivariable logistic regression was reported for the association of incident CKD with tertiles of dietary fibre intake. After adjustment for age, sex, smoking, total energy intake, physical activity, diabetes and using angiotensin-converting-enzyme inhibitor, the OR for subjects in the highest compared with the lowest tertile of total fibre intake was 0·47 (95 % CI 0·27, 0·86). In addition, for every 5 g/d increase in total fibre intake, the risk of incident CKD decreased by 11 %. After adjusting for potential confounders, OR for participants in the highest compared with the lowest tertile of fibre from vegetables was 0·63 (95 % CI 0·43, 0·93) and from legumes it was 0·68 (95 % CI 0·47, 0·98). We observed inverse associations between total fibre intake and risk of incident CKD, which demonstrate that high fibre intake, mainly from legumes and vegetables, may reduce the occurrence of CKD.

Associations between dairy food consumption and chronic kidney disease in older adults

We aimed to assess the association between dairy product consumption and calcium intake with the prevalence and 10-year incidence of chronic kidney disease (CKD). 1185 participants aged ≥50 years at baseline were examined between 1992–4 and 2002–4. Dietary data were collected using a food frequency questionnaire, and servings of dairy food consumption were calculated. Baseline biochemistry including serum creatinine was measured. CKD was defined as Modification of Diet in Renal Disease Study estimated glomerular filtration rate <60 mL·min^−1.1.73 m⁻². Cross-sectional analysis showed that older adults in the highest quintile compared to the lowest quintile (reference group) of low/reduced fat dairy food consumption had reduced odds of CKD, multivariable-adjusted odds ratio, OR, 0.64 (95% confidence intervals, CI, 0.43–0.96). Increasing total intake of dietary calcium was associated with reduced odds of CKD (P-trend = 0.02); comparing highest versus lowest quintile: OR 0.62 (95% CI 0.42–0.92). Participants in the second versus first quintile of low/reduced fat dairy food consumption at baseline had 49% reduced risk of CKD 10 years later, OR 0.51 (95% CI 0.29–0.89). Higher consumption of low/reduced fat dairy foods was independently associated with lower risk of CKD. Additional population-based studies are warranted to confirm these findings.

DASH dietary pattern and chronic kidney disease in elderly Korean adults

BACKGROUND/OBJECTIVES

Dietary patterns are linked to risk and outcomes in chronic kidney disease (CKD). Dietary intake varies by race, region and age. The relationship between a Dietary Approaches to Stop Hypertension (DASH) diet and CKD in elderly Koreans is unclear.

SUBJECTS/METHODS

We conducted cross-sectional analyses of 2408 community-dwelling elderly participants from the Korean National Health and Nutrition Examination Survey (2011-2012). DASH dietary patterns for six nutrients (protein, fiber, calcium, potassium, total fat and sodium) were collected by 24 h recall. DASH-US (based on the US recommendations) and DASH-KQ (Korean quartile) scores were generated by summing the scores for the six nutrients. Multivariate logistic regression analysis was used to calculate odds ratio (OR) for the association between a DASH diet and CKD.

RESULTS

Mean subject age was 72.4±5.1 years, 13.9% had CKD and 23.8% had diabetes. Protein, fiber, calcium and potassium intake was lower in CKD than non-CKD participants. In multivariate logistic regression analysis adjusted for age, sex, body mass index, comorbid conditions and other factors, a high DASH score was associated with a low odds for CKD based on DASH-US (OR=0.78, 95% confidence interval (CI), 0.65-0.94, P=0.009) and DASH-KQ (OR=0.95, 95% CI, 0.91-0.99, P=0.022). In six nutrients of DASH diet, high fiber intake showed a low odds for CKD in the DASH-KQ model (P for trend=0.010).

CONCLUSIONS

Our findings suggest that higher adherence to a DASH diet and higher fiber intake are associated with lower odds of CKD in elderly Koreans. These results should be corroborated through longitudinal studies of the association between a DASH diet and high-fiber diet on the risk of developing CKD.

Effect of glycemic index and carbohydrate intake on kidney function in healthy adults

BACKGROUND

Replacing carbohydrate with protein acutely increases glomerular filtration rate (GFR) but is associated with faster, long-term kidney disease progression. The effects of carbohydrate type (i.e. glycemic index, GI) on kidney function are unknown.

METHODS

We conducted an ancillary study of a randomized, crossover feeding trial in overweight/obese adults without diabetes or kidney disease (N = 163). Participants were fed each of four healthy, DASH-like diets for 5 weeks, separated by 2-week washout periods. Weight was kept constant. The four diets were: high GI (GI ≥65) with high %carb (58 % kcal) (reference diet), low GI (≤45) with low %carb (40 % kcal), low GI with high %carb; and high GI with low %carb. Plasma was collected at baseline and after each feeding period. Study outcomes were cystatin C, β2-microglobulin (β2M), and estimated GFR based on cystatin C (eGFRcys).

RESULTS

Mean (SD) age was 52 (11) years; 52 % were women; 50 % were black. At baseline, mean (SD) cystatin C, β2M, and eGFRcys were 0.8 (0.1) mg/L, 1.9 (0.4) mg/L, and 104 (16) mL/min/1.73 m(2). Compared to the high GI/high %carb diet, reducing GI, %carb, or both increased eGFRcys by 1.9 mL/min/1.73 m(2) (95 % CI: 1.1, 2.7; P < 0.001), 3.0 mL/min/1.73 m(2) (1.9, 4.0; P < 0.001), and 4.5 mL/min/1.73 m(2) (3.5, 5.4; P < 0.001), respectively. Increases in eGFRcys from reducing GI were significantly associated with increases in eGFRcys from reducing %carb (P < 0.001). Results for cystatin C and β2M reflected eGFRcys.

CONCLUSIONS

Reducing GI increased GFR. Reducing %carb by increasing calories from protein and fat, also increased GFR. Future studies on GI should examine the long-term effects of this increase in GFR on kidney injury markers and clinical outcomes.

TRIAL REGISTRATION

Clinical Trials.gov, number: NCT00608049 (first registered January 23, 2008).

Dietary Energy Density, Renal Function, and Progression of Chronic Kidney Disease

Background. There is evidence of the association between dietary energy density and chronic diseases. However, no report exists regarding the relation between DED and chronic kidney disease (CKD). Objective. To examine the association between dietary energy density (DED), renal function, and progression of chronic kidney disease (CKD). Design. Cross-sectional. Setting. Three nephrology clinics. Subjects. Two hundred twenty-one subjects with diagnosed CKD. Main Outcome Measure. Dietary intake of patients was assessed by a validated food frequency questionnaire. DED (in kcal/g) was calculated with the use of energy content and weight of solid foods and energy yielding beverages. Renal function was measured by blood urea nitrogen (BUN), serum creatinine (Cr), and estimated glomerular filtration rate (eGFR). Results. Patients in the first tertile of DED consumed more amounts of carbohydrate, dietary fiber, potassium, phosphorus, zinc, magnesium, calcium, folate, vitamin C, and vitamin B2. After adjusting for confounders, we could not find any significant trend for BUN and Cr across tertiles of DED. In multivariate model, an increased risk of being in the higher stage of CKD was found among those in the last tertile of DED (OR: 3.15; 95% CI: 1.30, 7.63; P = 0.01). Conclusion. We observed that lower DED was associated with better nutrient intake and lower risk of CKD progression.

Lifestyle factors and indices of kidney function in the Framingham Heart Study

BACKGROUND AND OBJECTIVES

Lifestyle characteristics are modifiable factors that could be targeted as part of chronic kidney disease (CKD) prevention. We sought to determine the association of lifestyle characteristics with incident estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) and rapid eGFR decline in older adults in the United States.

METHODS

Prospective cohort study of Framingham Offspring participants with baseline eGFR <60 ml/min/1.73 m(2) (n = 1,802) who attended the seventh (1998-2001; baseline) and eighth (2005-2008; follow-up) examinations (mean age = 59 years, 54.8% women). Predictors included measures of diet quality, physical activity, alcohol intake, and current smoking status assessed during baseline. Outcomes were based on creatinine-based eGFR at baseline and follow-up and included incident eGFR <60 ml/min/1.73 m(2) (at follow-up) and rapid eGFR decline (annual eGFR decrease ≥3 ml/min/1.73 m(2)).

RESULTS

Over an average follow-up of 6.6 years, 9.5% (n = 171) of participants developed incident eGFR <60. A trend was observed across quartiles of diet quality, with higher levels of diet quality associated with a decreased odds ratio (OR) of incident eGFR <60 (p trend = 0.045). Higher diet quality was associated with decreased odds of rapid eGFR decline (p trend = 0.03) and was attenuated with additional adjustment (p trend = 0.07). In sensitivity analysis for rapid eGFR decline using a secondary definition (annual eGFR decrease ≥3 and incident eGFR <60), diet associations remained significant with additional adjustment (p trend = 0.04). No associations were observed with physical activity, smoking status, or alcohol intake with incident eGFR <60 or rapid eGFR decline (all p > 0.19).

CONCLUSIONS

Higher diet quality may be associated with a decreased risk of incident eGFR <60 ml/min/1.73 m(2), and rapid eGFR decline. Whether adherence to a healthy diet can prevent reduction in kidney function warrants further study.

Perceived barriers and facilitators of using dietary modification for CKD prevention among African Americans of low socioeconomic status: a qualitative study

Background

Factors influencing the use of dietary interventions for modification of CKD risk among African Americans have not been well-explored. We assessed perceived barriers and facilitators of CKD prevention through dietary modifications among African Americans with low socioeconomic status (SES) and at high risk for CKD.

Methods

We conducted a qualitative study involving three 90 minute focus groups of low SES (limited education, unemployed, uninsured, or income < $25,000/year) African American residents of Baltimore, Maryland (N = 17), who were aged 18-60 years, with no known history of CKD and (1) a family history of end stage renal disease and (2) self-reported diabetes, hypertension, cardiovascular disease, HIV or obesity. A trained moderator asked a series of 21 closed and open-ended questions. Group sessions were recorded, transcribed, and two independent investigators reviewed transcripts to identify common themes.

Results

Participants’ mean (SD) age was 39.8 (12.4) years. Most (59%) were female and earned < $5,000/year (71%). One quarter (24%) had self-reported diabetes and over half had hypertension (53%). Few (12%) perceived their CKD risk as high. Perceived barriers to CKD prevention through dietary change included the expense and unavailability of healthy foods, family member preferences, convenience of unhealthy foods, and inability to break lifelong habits. They identified vouchers for healthy foods, family-based interventions, nutritional counseling and group gatherings for persons interested in making dietary changes as acceptable facilitators of dietary CKD prevention efforts.

Conclusions

Low SES African Americans at high risk for CKD had limited perception of their risk but they identified multiple barriers and potential facilitators of CKD prevention via dietary modifications which can inform future studies and public health interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2369-15-194) contains supplementary material, which is available to authorized users.

A better diet quality is associated with a reduced likelihood of CKD in older adults

BACKGROUND AND AIMS

Studies of diet in relation to chronic kidney disease (CKD) have focused on individual nutrients. The relationship between overall patterns of food intake and renal function has not been well explored. We aimed to investigate the associations between diet quality with the prevalence, incidence and progression of CKD in a cohort of older adults.

METHODS AND RESULTS

1952 participants aged ≥50 years at baseline were examined between 1992-1994 and 2002-2004. Dietary data were collected using a semi-quantitative food frequency questionnaire. A modified version of the Healthy Eating Index for Australians was developed to determine total diet scores (TDS). Baseline biochemistry including serum creatinine was measured. CKD was defined as MDRD estimated glomerular filtration rate (eGFR) <60 mL min⁻¹·1.73 m⁻². Participants in the highest quartile of mean TDS compared to those in the first quartile (reference), had a 41% reduced likelihood of having eGFR <60 mL min⁻¹·1.73 m⁻², [multivariable-adjusted odds ratio, OR, 0.59 (95% confidence intervals, CI, 0.41-0.85), P-trend = 0.005]. Each unit increase in TDS was associated with a 15% decrease in the odds of having prevalent CKD, multivariable-adjusted OR 0.85 (95% CI 0.74-0.97). A non-significant, inverse association between TDS and CKD incidence was observed (P-trend = 0.10).

CONCLUSION

Older adults with better diet quality had a reduced likelihood of having eGFR <60 mL min⁻¹·1.73 m⁻². Adherence to dietary guidelines were not prospectively associated with CKD incidence or progression. Further studies with adequate power are warranted to assess the longitudinal association between diet quality and CKD.

Is glycaemic index (GI) a valid measure of carbohydrate quality?

Recent criticisms of the glycaemic index (GI) focus on its validity with assertions that GI methodology is not valid, GI values are inaccurate and imprecise, GI does not predict what foods are healthy and that whole grain and fibre are better markers of carbohydrate quality than GI. None of the critics provide sound reasons for rejecting GI because some of their arguments are based on flagrant errors in understanding and interpretation while others are not supported by current data or are inconsistent with other nutritional recommendations. This paper addresses current criticisms of GI and outlines reasons why GI is valid: (1) GI methodology is accurate and precise enough for practical use; (2) GI is a property of foods; and (3) GI is biologically meaningful and relevant to virtually everyone. Current dietary guidelines recommend increased consumption of whole grains and dietary fibre but do not mention GI. However, this is illogical because the evidence that GI affects health outcomes is at least as good or better than that for whole grains and fibre. GI is a novel concept from a regulatory point of view and a number of problems need to be addressed to successfully translate GI knowledge into practice. The problems are not insurmountable but no progress can be made until bias and misunderstanding about GI can be overcome and there is better agreement about what is the actual state of knowledge on GI so that the real issues can be identified and addressed.

Natural history of age-related retinal lesions that precede AMD in mice fed high or low glycemic index diets

PURPOSE

Epidemiologic data indicate that people who consume low glycemic index (GI) diets are at reduced risk for the onset and progression of age-related macular degeneration (AMD). The authors sought corroboration of this observation in an animal model.

METHODS

Five- and 16-month-old C57BL/6 mice were fed high or low GI diets until they were 17 and 23.5 months of age, respectively. Retinal lesions were evaluated by transmission electron microscopy, and advanced glycation end products (AGEs) were evaluated by immunohistochemistry.

RESULTS

Retinal lesions including basal laminar deposits, loss of basal infoldings, and vacuoles in the retinal pigment epithelium were more prevalent in the 23.5- than in the 17-month-old mice. Within each age group, consumption of a high GI diet increased the risk for lesions and the risk for photoreceptor abnormalities and accumulation of AGEs.

CONCLUSIONS

Consuming high GI diets accelerates the appearance of age-related retinal lesions that precede AMD in mice, perhaps by increasing the deposition of toxic AGEs in the retina. The data support the hypothesis that consuming lower GI diets, or simulation of their effects with nutraceuticals or drugs, may protect against AMD. The high GI-fed C57BL/6 mouse is a new model of age-related retinal lesions that precede AMD and mimic the early stages of disease and may be useful for drug discovery.