There are some claims that, because hydroxyapatite contains other minerals and constituents from natural bone, it works better for bone health than other calcium supplements. However, there’s currently no convincing evidence to prove this. Studies have not found higher calcium absorption from osseo-hydroxyapatite or microcrystalline hydroxyapatite supplementation than from supplementation with other calcium salts, such as calcium citrate.[1][2]
A meta-analysis from 2009 of six small studies does suggest that taking osseo-hydroxyapatite results in a 1% greater bone mineral density (BMD) over 1-3 years compared to taking calcium carbonate.[3] However, this analysis is of limited use because of inclusion of unpublished studies, low study quality (e.g. lack of blinding), and possible presence of financial bias. Furthermore, a 1% increase in BMD over 1-3 years is not enough to prevent fractures, which are the key clinical outcome in bone health.[4]