Acute and 3-month effects of microcrystalline hydroxyapatite, calcium citrate and calcium carbonate on serum calcium and markers of bone turnover: a randomised controlled trial in postmenopausal women.

Study answer

What this study found

Overall, calcium supplementation lowered bone turnover, and microcrystalline hydroxyapatite appeared to be as effective as conventional calcium salts over 3 months. After the first dose, ionised and total calcium increased in the citrate and carbonate groups and in the microcrystalline hydroxyapatite groups versus control, but the ionised calcium rise and AUC were greater with citrate-carbonate than with MCH. After 3 months, CTX and PINP were significantly lower than baseline in the citrate-carbonate and MCH groups, with no difference in the magnitude of reduction between them. MCH produced…

Study & population

Randomized controlled trial in postmenopausal women at least 5 years after menopause, without cardiovascular disease or major systemic illness, recruited in New Zealand from volunteers for other osteoporosis studies.

Intervention

Participants received oral calcium supplements as encapsulated powders, providing 1 g elemental calcium per day in two divided doses for 3 months.

Key limitation

Small per-arm sample sizes, a short 3-month follow-up, and reliance on biochemical surrogate outcomes rather than fractures limit interpretation.

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Original abstract