Mineral water as a source of dietary calcium: acute effects on parathyroid function and bone resorption in young men

Background: Calcium is a major component, of mineralized tissues and is required for normal growth and maintenance of bone. Epidemiologic studies showed that a large percentage of the population fails to meet the currently recommended guidelines for optimal calcium intake. Objective: The present study was designed to determine whether high-calcium mineral water is an efficient additional source of dietary calcium. Design: Twelve healthy young men (mean [+ or -] SD age: 21.1 [+ or -] 1.2 y) ingested in a randomized order either 0.5 L of a mineral water containing 344 mg Ca/L or 0.5 L of a mineral water with a very low concentration of calcium ([is less than] 10 mg/L) as a control. Blood samples were drawn before and 1, 2, 3, and 4 h after intake of the water. Urine was collected for 2 h before and every 2 h for 4 h after ingestion of the water. Serum concentrations of intact parathyroid hormone (iPTH) and serum concentrations and urinary excretion of a recently developed biochemical marker of bone resorption, type 1 collagen cross-linked C-telopeptide (CTx), were measured. Results: Serum iPTH was significantly (P [is less than] 0.002) lower after ingestion of high-calcium water than after ingestion of the control. There was a significant (P = 0.01) progressive decrease in urinary CTx after ingestion of the high-calcium water, whereas after ingestion of low-calcium water the changes were modest and not significant. The fall in serum CTx concentrations was 34.7% 3 h after ingestion of high-calcium water, compared with 17.6% with the control. The decreases in serum CTx concentrations were significantly (P [is less than] 0.05) lower 1, 2, 3, and 4 h after ingestion of high-calcium water than after ingestion of the control. Conclusion: The present study showed that one oral intake of water containing a very moderate dose of calcium (172 mg) acutely inhibited iPTH secretion and bone resorption. Am J Clin Nutr 2000; 71: 999-1002. KEY WORDS Calcium, parathormone, bone markers, mineral water, young men, France, parathyroid hormone, parathyroid function, bone resorption