Comparison of the effects of calcium loading with calcium citrate or calcium carbonate on bone turnover in postmenopausal women
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Calcium supplementation is known to increase bone mineral density and decrease fractures, but the relative efficacy of different forms of calcium supplementation is not established. We compared the effects of calcium carbonate and calcium citrate on markers of bone resorption in older postmenopausal women in an open-labeled crossover study. Forty women were randomized to receive 1000 mg/day of either calcium citrate or calcium carbonate for 12 weeks, followed by a 2-week washout without calcium supplements and 12 weeks treatment with the alternate calcium supplement. All women received vitamin D (900 IU/day). Thirty-four women (25 Caucasian, nine Hispanic) completed the study. No significant differences in the decrease in parathyroid hormone (PTH) or bone specific alkaline phosphatase or the increase in urinary calcium/creatinine were detected between the two treatments. However, calcium citrate supplementation decreased the collagen cross-link resorption markers, urinary N-telopeptide (−30%), C-telopeptide (−31%), free deoxypyridinoline (19%) and serum N-telopeptide (−8%), compared to no significant change following calcium carbonate supplementation (+2%, +3%, +2% and +2%, respectively; P<0.05). Calcium citrate decreased markers of bone resorption significantly more than calcium carbonate in postmenopausal women, although no differences in their effects in calcium excretion or PTH were detected.
KeywordsCalcium carbonate Calcium citrate Markers of bone formation Markers of bone resorption
This work has been supported by the General Clinical Research Center (MO1-RR06192), Claude Pepper OAIC (5P60-AG13631) and Mission Pharmacal. Dr. Kenny has been supported by the Paul Beeson Faculty Scholar Program. In addition, we wish to thank Pamela Fall and Christine Abreu for assistance in the biochemical assays.
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