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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Adult, Alkaline Phosphatase, Bed Rest, Bone Remodeling, Bone and Bones, Calcium, Calcium, Dietary, Collagen Type I, Cross-Over Studies, Humans, Male, Parathyroid Hormone, Peptide Fragments, Peptides, Procollagen.
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Does short-term high dietary calcium intake during bedrest have no effect on markers of bone turnover in healthy men? Context: Immobilization and space flight are causes of disuse osteoporosis. Increasing calcium intake may counteract this disuse-induced bone loss. We conducted two bedrest experiments (crossover design: bedrest versus ambulatory control) in a metabolic ward, studying the effect of 1000 mg/d of calcium intake (study A, length of intervention 14 d) compared with that of a high calcium intake of 2000 mg/d (study B, 6 d) on markers of bone turnover. Both studies were randomized, controlled studies with the subjects staying under well-controlled environmental conditions (study A, 9 male subjects, age 23.6+/-3.0 y; study B, 8 male subjects, age 25.5+/-2.9 y). Blood was drawn to analyze serum calcium, parathyroid hormone, procollagen type I C-terminal propeptide, and bone alkaline phosphatase. Urine (24-h) was collected for analysis of calcium, C-terminal telopeptide of collagen type I, and N-terminal telopeptide of collagen type I. In both studies, serum calcium levels remained unchanged. Procollagen type I C-terminal propeptide was lower (P=0.03) in the bedrest phase than in the ambulatory phase in study A and tended to be lower (P=0.08) in bedrest in study B, whereas bone alkaline phosphatase was not affected in either study. Urinary calcium excretion was greater during bedrest than during the ambulatory phase (study A, P=0.005; study B, P=0.002). C-terminal telopeptide of collagen type I excretion was also greater during bedrest in both studies (study A, P<0.001; study B, P<0.001).
assistant
Doubling calcium intake to 2000 mg/d does not prevent increased bone resorption induced by bedrest. Final Decision: yes