Metabolic acidosis causes bone loss and muscle wasting. On a daily basis, adults on normal Western diets generate approximately 75-100 meq/d of acid. As individuals age, their renal function and ability to excrete acid decline and they become more acidotic. Alkalinizing the diet with supplemental potassium bicarbonate (KHCO3) reduces urinary calcium excretion, lowers bone turnover rates (biochemical markers of bone resorption) and reduces urinary nitrogen excretion (an indicator of muscle catabolism) acutely in subjects on acidogenic metabolic diets. Currently there is no concensus on the relative contributions of potassium (which may increase renal calcium retention) and bicarbonate (shown to reduce net acid excretion) on decreasing bone turnover. We postulate that HCO3 may also reduce N2 (muscle) wasting in older persons. There is no evidence at this time that KHCO3 or its components will have a sustained impact on bone turnover or nitrogen wasting under field conditions.The proposed study will determine the effect of potassium and bicarbonate, alone and in combination, on serum PTH, biochemical markers of bone turnover, calcium excretion, calcium absorption and urinary nitrogen. 192 men and women will be randomly assigned to treatment with 67.5 mmol of KHC03, KCI, or NaHCOS or with placebo daily for 12 weeks. Subjects will visit the Center at baseline, 3, 7, and 12 weeks for assessment of their diets, pill compliance, and weight. They will have the following measurements on selected study visits: muscle function tests, serum calcium, potassium, parathyroid hormone, and osteocalcin and 24-hr urinary calcium, N-telopeptide, calcium absorption, potassium, sodium, creatinine, titratable acid, renal net acid excretion, and nitrogen. In the analysis, the final value will be the response and the baseline value will be a covariate. If effective in reducing calcium excretion, bone turnover, and/or nitrogen wasting, then treatment with potassium, bicarbonate, or the two combined would warrant further evaluation as a potentially inexpensive and safe means to reduce bone loss and muscle wasting in the elderly.
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