EFFECTS OF MINERAL-COMPOSITION OF DRINKING-WATER ON RISK FOR STONE FORMATION AND BONE METABOLISM IN IDIOPATHIC CALCIUM NEPHROLITHIASIS

1. To assess whether the mineral content of drinking water influences both risk of stone formation and bone metabolism in idiopathic calcium nephrolithiasis, 21 patients were switched from their usual home diet s to a 10 mmol calcium, low-oxalate, protein-controlled diet, suppleme nted with 21 of three different types of mineral water, Drinking water added 1, 6 and 20 mmol of calcium and 0.5, 10 and 50 mmol of bicarbon ate respectively to the controlled diet. 2. The three controlled study periods lasted 1 month each and were separated by a 20 day washout in terval. Blood and urine chemistries, including intact parathyroid horm one, calcitriol and two markers of bone resorption, were performed at the end of each study period. The stone-forming risk was assessed by c alculating urine saturation with calcium oxalate (beta CaOx), calcium phosphate (beta bsh) and uric acid (beta UA). 3. The addition of any m ineral water produced the expected increase in urine output and was as sociated with similar decreases in beta CaOx and beta UA, whereas beta bsh varied marginally. These equal decreases in beta CaOx, however, r esulted from peculiar changes in calcium, oxalate and citrate excretio n during each study period. The increase in overall calcium intake due to different drinking water induced increases in calcium excretion, w hereas excretion tended to decrease. The changes in oxalate excretion during any one study period compared with another were significantly r elated to those in calcium intake. Citrate excretion was significantly higher with the high-calcium, alkaline water. 4. Parathyroid hormone, calcitriol and markers of bone resorption increased when patients wer e changed from the high-calcium, alkaline to the low-calcium drinking water. 5. We suggest that overall calcium intake may be tailored by su pplying calcium in drinking water. Adverse effects on bone turnover wi th low-calcium diets can be prevented by giving high-calcium, alkaline drinking water, and the stone-forming risk can be decreased as effect ively as with low-calcium drinking water.