Arterialized venous bicarbonate is associated with lower bone mineral density and an increased rate of bone loss in older men and women

Context: Higher dietary net acid loads have been associated with increased bone resorption, reduced bone mineral density (BMD), and increased fracture risk. Objective: The objective was to compare bicarbonate (HCO₃) measured in arterialized venous blood samples to skeletal outcomes. Design: Arterialized venous samples collected from participants in the Health, Aging and Body Composition (Health ABC) Study were compared to BMD and rate of bone loss. Setting: The setting was a community-based observational cohort. Participants: A total of 2287 men and women age 74 ± 3 years participated. Intervention: Arterialized venous blood was obtained at the year 3 study visit and analyzed for pH and pCO₂. HCO₃ was determined using the Henderson-Hasselbalch equation. Main Outcome Measure: BMD was measured at the hip by dual-energy x-ray absorptiometry at the year 1 (baseline) and year 3 study visits. Results: Plasma HCO₃ was positively associated with BMD at both year 1 (P <.001) and year 3 (P <.001) in models adjusted for age, race, sex, clinic site, smoking, weight, and estimated glomerular filtration rate. Plasma HCO₃ was inversely associated with rate of bone loss at the total hip over the 2.1 ± 0.3 (mean ± SD) years between the two bone density measurements (P =.001). Across quartiles of plasma HCO₃, the rate of change in BMD over the 2.1 years ranged from a loss of 0.72%/y in the lowest quartile to a gain of 0.15%/y in the highest quartile of HCO₃. Conclusions: Arterialized plasma HCO₃ was associated positively with cross-sectional BMD and inversely with the rate of bone loss, implying that systemic acid-base status is an important determinant of skeletal health during aging. Ongoing bone loss was linearly related to arterialized HCO₃, even after adjustment for age and renal function. Further research in this area may have major public health implications because reducing dietary net acid load is possible through dietary intervention or through supplementation with alkaline potassium compounds.