Dietary Acid Load, Kidney Function and Disability in Elderly

Physical decline and frailty result from age- and disease-related impairments in organs and tissues. Frailty research has focused on the musculoskeletal, neurological and circulatory systems; yet interventions targeting these systems had limited success in preventing and treating functional decline. Given the aging of the US population, additional avenues for intervention development are urgently needed. Fragility and disability in people ≥65 strongly correlate with declining kidney function and are evident even in early stages of chronic kidney disease (CKD). Moreover, CKD is highly prevalent in the elderly and associates with sarcopenia, osteopenia, and increased incidence of fractures/falls with hospitalization. Low serum bicarbonate and impaired acid-base homeostasis, also common in CKD, are increasingly appreciated as contributors to functional decline with advancing age. With aging, the adaptive response of the kidney to low serum bicarbonate and high metabolic acid load becomes maladaptive, facilitating CKD progression. Conversely, in adult patients with CKD, maintenance of serum bicarbonate at 24 meq/L with oral bicarbonate supplementation or increased consumption of base-forming foods slows CKD progression. The study investigators propose the current study and protocol based on the evidence summarized above and our preliminary studies, which suggest that: In the Health Aging and Body Composition cohort (age 70-79) lower dietary acid load associates with stable kidney function over a 7-year follow-up, independent of age, race, gender, BMI, diabetes, hypertension or smoking status; metabolomics analysis in participants of the African American Diabetes Heart Study suggested that it is feasible to segregate a urine metabolomics profile in the early stages of CKD (stages 2 and 3), and that lower consumption of base-forming fruits and vegetables and higher rates of acid excretion may be associated with CKD and its progression. The investigators therefore hypothesized that decreasing metabolic acid production by titrating dietary acid load may ameliorate the generally expected, age-related decline in kidney function, decrease loss of lean body mass, preserve physical function, and ameliorate disability. This is not a treatment study as the investigators are exploring the effects of bicarbonate on these age-related issues.