Dietary acid load: a novel nutritional target in chronic kidney disease?

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.

Mineral bone disease in maintenance hemodialysis patients: Association with morbidity and mortality

There is a paucity of data on mineral bone disease in maintenance hemodialysis (MHD) patients from India. This retrospective analysis was undertaken on 858 (males: 599; females: 259) patients from two medical centers on MHD from 1998 to 2010. Age, gender, months on dialysis, hours per session of dialysis, hemoglobin, serum calcium, inorganic phosphorus, intact parathyroid hormone (iPTH), urine output, erythropoietin dosage per week, blood sugar, blood pressure, urea reduction rate, gain in fluid and fluid removed per session, serum albumin, alkaline phosphatase, vitamin D level, supplemental vitamin D and use of phosphate binder for therapy were documented. Overall, 191 patients died (22%) during the observation period. There was an 86% patient survival rate at 1 year on dialysis and an overall predicted 3-year survival rate of 78%. A relatively higher iPTH (P = 0.012), a need for vitamin D supplementation (P = 0.003), less hours on dialysis per session (P = 0.046) and a non-vegetarian diet (P = 0.022) were significantly associated with mortality.

Dietary acid load, insulin sensitivity and risk of type 2 diabetes in community-dwelling older men

AIMS/HYPOTHESIS

We tested the hypothesis that dietary acid load may increase the risk of type 2 diabetes, and studied the association between acid load and insulin sensitivity as a possible mechanism involved.

METHODS

An observational survey with prospective follow-up including 911 non-diabetic Swedish men aged 70-71 years was carried out. The gold standard euglycaemic-hyperinsulinaemic clamp technique and the OGTT were used to determine insulin sensitivity and beta cell function, respectively. Diabetes incidence was assessed during 18 years of follow-up. Renal function was estimated from serum cystatin C concentrations. Dietary acid load was calculated as potential renal acid load (PRAL) and net endogenous acid production (NEAP) algorithms from 7 day food records. Adequate dietary reporters were identified by Goldberg cut-offs.

RESULTS

PRAL and NEAP were not associated with insulin sensitivity or beta cell function. Underlying kidney function or consideration of dietary adequate reporters did not modify these null findings. During follow-up, 115 new cases of diabetes were validated. Neither PRAL nor NEAP was associated with diabetes incidence.

CONCLUSIONS/INTERPRETATION

Our results do not support the hypothesis that dietary acid load influences insulin sensitivity, beta cell function or diabetes risk. Interventional studies modifying acid-base dietary intake are needed to further elucidate a possible role of acid load in the development of type 2 diabetes.

Low serum bicarbonate and kidney function decline: the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Among populations with established chronic kidney disease (CKD), metabolic acidosis is associated with more rapid progression of kidney disease. The association of serum bicarbonate concentrations with early declines in kidney function is less clear.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

5,810 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) with a baseline estimated glomerular filtration rate (eGFR) > 60mL/min/1.73 m(2) using the CKD-EPI (CKD Epidemiology Collaboration) creatinine-cystatin C equation.

PREDICTORS

Serum bicarbonate concentrations.

OUTCOMES

Rapid kidney function decline (eGFR decline > 5% per year) and incident reduced eGFR (eGFR < 60mL/min/1.73 m(2) with minimum rate of eGFR loss of 1 mL/min/1.73 m(2) per year).

RESULTS

Average bicarbonate concentration was 23.2 ± 1.8mEq/L. 1,730 (33%) participants had rapid kidney function decline, and 487 had incident reduced eGFR during follow-up. Each 1-SD lower baseline bicarbonate concentration was associated with 12% higher adjusted odds of rapid kidney function decline (95% CI, 6%-20%) and higher risk of incident reduced eGFR (adjusted incidence rate ratio, 1.11; 95% CI, 1.03-1.20) in models adjusting for demographics, baseline eGFR, albuminuria, and CKD risk factors. The OR for the associations of bicarbonate level < 21 mEq/L relative to 23-24 mEq/L was 1.35 (95% CI, 1.05-1.73) for rapid kidney function decline, and the incidence rate ratio was 1.16 (95% CI, 0.83-1.62) for incident reduced eGFR.

LIMITATIONS

Cause of metabolic acidosis cannot be determined in this study.

CONCLUSIONS

Lower serum bicarbonate concentrations are associated independently with rapid kidney function decline independent of eGFR or albuminuria in community-living persons with baseline eGFR > 60 mL/min/1.73 m(2). If confirmed, our findings suggest that metabolic acidosis may indicate either early kidney disease that is not captured by eGFR or albuminuria or may have a causal role in the development of eGFR < 60 mL/min/1.73 m(2).

Metabolic acidosis and the progression of chronic kidney disease

Metabolic acidosis is a common complication of chronic kidney disease. Accumulating evidence identifies acidosis not only as a consequence of, but as a contributor to, kidney disease progression. Several mechanistic pathways have been identified in this regard. The dietary acid load, even in the absence of overt acidosis, may have deleterious effects. Several small trials now suggest that the treatment of acidosis with oral alkali can slow the progression of kidney disease.

Effect of food insecurity on chronic kidney disease in lower-income Americans

BACKGROUND

The relation of food insecurity (inability to acquire nutritionally adequate and safe foods) and chronic kidney disease (CKD) is unknown. We examined whether food insecurity is associated with prevalent CKD among lower-income individuals in both the general US adult population and an urban population.

METHODS

We conducted cross-sectional analyses of lower-income participants of the National Health and Nutrition Examination Survey (NHANES) 2003-2008 (n = 9,126) and the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study (n = 1,239). Food insecurity was defined based on questionnaires and CKD was defined by reduced estimated glomerular filtration rate or albuminuria; adjustment was performed with multivariable logistic regression.

RESULTS

In NHANES, the age-adjusted prevalence of CKD was 20.3, 17.6, and 15.7% for the high, marginal, and no food insecurity groups, respectively. Analyses adjusting for sociodemographics and smoking status revealed high food insecurity to be associated with greater odds of CKD only among participants with either diabetes (OR = 1.67, 95% CI: 1.14-2.45 comparing high to no food insecurity groups) or hypertension (OR = 1.37, 95% CI: 1.03-1.82). In HANDLS, the age-adjusted CKD prevalence was 5.9 and 4.6% for those with and without food insecurity, respectively (p = 0.33). Food insecurity was associated with a trend towards greater odds of CKD (OR = 1.46, 95% CI: 0.98-2.18) with no evidence of effect modification across diabetes, hypertension, or obesity subgroups.

CONCLUSION

Food insecurity may contribute to disparities in kidney disease, especially among persons with diabetes or hypertension, and is worthy of further study.