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Calcium phosphate

Also known as: Calcium phosphate, CaP, hydroxyapatite, tricalcium phosphate, dicalcium phosphate

Overview

Calcium phosphate refers to a group of calcium salts of phosphoric acid, including hydroxyapatite (Ca_10(PO_4)_6(OH)_2), tricalcium phosphate (Ca_3(PO_4)_2), and dicalcium phosphate (CaHPO_4). It is a mineral compound naturally found in bone and teeth, providing structural rigidity, and is also present in dietary sources such as dairy products. Primarily used as a supplement to support bone health, it aims to improve bone mineral density (BMD) and bone mineral content (BMC), and for the prevention and treatment of osteoporosis. It also serves as a biomaterial in bone graft substitutes for orthopedic and dental applications. Calcium phosphate provides essential calcium and phosphate ions for bone mineralization, is biocompatible, and osteoconductive. Research on calcium phosphate is extensive, with high-quality evidence from numerous randomized controlled trials and meta-analyses supporting its efficacy and safety in bone health.

Benefits

Calcium phosphate supplementation significantly improves bone mineral density (BMD) and bone mineral content (BMC), particularly at clinically relevant sites such as the femoral neck and lumbar spine. A meta-analysis of 7,382 participants showed consistent BMD/BMC improvements, especially with supplementation durations of 18 months or longer. These improvements are statistically significant and clinically relevant in reducing fracture risk. Calcium phosphate-based biomaterials, especially when supplemented with bioinorganics like strontium, magnesium, or silica, enhance new bone formation in animal models, showing a strong effect on bone regeneration with a standardized mean difference (SMD) of 1.43. Young individuals under 35 years can benefit from calcium phosphate supplementation to achieve peak bone mass, while older adults may benefit from combined calcium and vitamin D supplementation to reduce fracture risk. Benefits on bone density are more pronounced with longer, sustained supplementation.

How it works

Calcium phosphate provides bioavailable calcium and phosphate ions, which are crucial for the formation of hydroxyapatite crystals within the bone matrix. This process facilitates mineralization and enhances bone strength. By contributing to the bone remodeling and repair processes, it supports the integrity of the skeletal system. While it does not have direct receptor-mediated effects, its presence influences osteoblast and osteoclast activity indirectly by ensuring adequate mineral availability. Calcium phosphate is moderately bioavailable, and its absorption can be significantly enhanced by co-supplementation with vitamin D, which plays a critical role in calcium uptake and utilization by the body.

Side effects

Calcium phosphate supplementation is generally safe, with meta-analyses indicating no significant increase in cardiovascular disease risk. Common side effects, experienced by more than 5% of individuals, are typically mild gastrointestinal discomforts such as constipation and bloating. Uncommon side effects (1-5%) include rare cases of hypercalcemia, which may occur with excessive doses or in predisposed individuals. Rare side effects (less than 1%) include kidney stones, though these are uncommon with appropriate dosing. Calcium phosphate may interact with certain medications, potentially interfering with the absorption of antibiotics (e.g., tetracyclines, quinolones) and bisphosphonates if taken simultaneously. Contraindications include existing hypercalcemia, severe renal impairment, and hypersensitivity to calcium phosphate compounds. Caution is advised for patients with renal disease, and vitamin D status should be monitored to optimize calcium absorption and minimize risks.

Dosage

For bone health benefits, typical calcium doses from supplements range from 500–1000 mg/day, with calcium phosphate formulations providing variable elemental calcium content. The optimal dosage range for adults is generally 1000–1300 mg of elemental calcium daily, adjusted based on dietary intake. To avoid adverse effects, the total daily calcium intake (from diet and supplements) should not exceed 2000–2500 mg. Dividing the daily dose can improve absorption. Co-administration with vitamin D is crucial as it significantly enhances calcium absorption and efficacy. Calcium phosphate supplements vary in elemental calcium content; for instance, hydroxyapatite forms may have slower absorption but better bone integration when used as biomaterials. Vitamin D sufficiency is critical for absorption, and high dietary phytate or oxalate can reduce it.

FAQs

Is calcium phosphate supplementation safe for cardiovascular health?

Yes, meta-analyses indicate no significant increase in the risk of coronary heart disease or stroke with calcium supplementation.

How long does it take to see bone density improvements?

Significant improvements typically require at least 18 months of consistent supplementation to become evident.

Can calcium phosphate be used in bone grafts?

Yes, calcium phosphate-based biomaterials are widely used in bone graft substitutes, and their performance can be enhanced with bioinorganic supplementation.

Is vitamin D necessary with calcium phosphate?

Yes, vitamin D is essential as it significantly improves calcium absorption and overall bone health outcomes.

Are there risks of kidney stones?

The risk of kidney stones is low but may increase with excessive calcium intake or if an individual is predisposed.

Research Sources

https://elifesciences.org/articles/79002 – This systematic review and meta-analysis, including 7,382 participants, found that calcium supplementation significantly improves bone mineral density (BMD) and bone mineral content (BMC), particularly at the femoral neck, with benefits becoming more pronounced after 18 months of supplementation. The study highlights the importance of sustained intake for achieving clinically relevant bone health improvements in young individuals.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10111600/ – This meta-analysis of randomized controlled trials concluded that calcium supplementation does not significantly increase the risk of cardiovascular disease, including coronary heart disease or stroke, in adults. The findings provide reassurance regarding the cardiovascular safety profile of calcium supplements, although it noted limitations in data for vitamin D deficient populations.
https://pubs.rsc.org/en/content/articlelanding/2020/bm/d0bm00599a – This systematic review and meta-analysis of animal studies demonstrated that supplementing calcium phosphate-based biomaterials with bioinorganics (e.g., strontium, magnesium, silica) significantly enhances new bone formation in preclinical bone defect models. The study reported a standardized mean difference of 1.43, indicating a strong positive effect on bone regeneration, though caution is advised for direct human translation.
https://pubmed.ncbi.nlm.nih.gov/32729591/ – This publication, likely a related or duplicate entry to the RSC Advances paper, also focuses on the enhancement of calcium phosphate biomaterials with bioinorganics for bone regeneration. It reinforces the finding that such modifications can significantly improve bone formation in animal models, supporting the potential for advanced bone graft substitutes.
https://www.bonehealthandosteoporosis.org/wp-content/uploads/2016/10/Evidence-Review.pdf – This evidence review, likely from a bone health organization, provides a comprehensive overview of calcium and vitamin D's role in bone health. It supports the use of calcium, often in combination with vitamin D, for maintaining bone mineral density and reducing fracture risk, particularly in older adults, aligning with the general understanding of calcium phosphate's benefits.