Dietary acid-base balance, bone resorption, and calcium excretion

Objective: Metabolic studies reveal that acidogenic diets increase bone resorption acutely. This study was conducted to examine associations between diet-induced changes in net acid excretion (NAE) and changes in serum parathyroid hormone (PTH), bone resorption, and calcium excretion over a longer period of 60 days. Methods: Forty healthy older men and women were given 0.75 g/kg of protein as meat, 600 mg of calcium, and 400 IU of vitamin D-3 daily and either cereal (acidogenic) or fruit and vegetable (alkalinogenic) foods as substitutes for some of the cereal in their usual diets. Blood and 24-hr urine measurements were made on days 14 (baseline), 44, and 74. Results: In all subjects, change in renal NAE was correlated with changes in serum PTH (r = 0.358, P = 0.023), urinary N-telopeptide (NTX) (r = 0.367, P = 0.020), and urinary calcium excretion (r(P) = 0.381, P = 0.020, after adjustment for diet group, change in PTH, and change in sodium excretion). Conclusions: Diet changes that increase renal NAE are associated with increases in serum PTH, bone resorption, and calcium excretion over a 60-day period.