Objective: To investigate calcium supplements in postmenopausal women. Calcium supplements in postmenopausal women with a low calcium intake have been shown to prevent osteoporotic vertebral fracture, but calcium is variably absorbed and often poorly tolerated, which may limit effectiveness.
Methods: The study compared the efficacy and tolerability of 500 mg/day of calcium in the form of ossein-hydroxyapatite (OHC) versus 500 mg/day of tricalcium phosphate (TCP) and placebo in the prevention of postmenopausal bone loss. This was a prospective randomized study enrolling 153 postmenopausal osteopenic women. Serum and urine markers of bone turnover were collected at 3 and 6 months. Bone density measurement was performed at baseline and 6 months in all participants, and at 12 months in women taking OHC.
Results: At 3 and 6 months, both TCP and OHC decreased serum markers of bone formation significantly, compared with placebo. At 6 months, TCP and OHC decreased osteocalcin by 9.9% and 12.3%, respectively; the aminoterminal propeptide of type I procollagen (PINP) was decreased by 5.3% and 6.3%, respectively; bone-specific alkaline phosphatase was decreased by 4.3% and 6.7%, respectively, compared with baseline. The effects on bone resorption markers or on bone mineral density did not reach statistical significance, although OHC increased bone density by 0.8% at the spine at 12 months. Both forms of calcium were well tolerated and did not differ from placebo in terms of side-effects.
Conclusions: While both OHC and TCP were well tolerated and significantly reduced bone turnover markers, the effect of ossein-hydroxyapatite seems slightly superior to that of tricalcium phosphate.