Calcium
Plain-language research summary.
Detail
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Essential mineral for bone strength, nerve signaling, and muscle contraction — foundational for skeletal health, especially in women post-menopause.
Common Dietary Sources
- Dairy (milk, yogurt, cheese)
- Small fish with edible bones (sardines, salmon)
- Dark leafy greens (kale, collards, bok choy)
- Fortified plant milks and cereals
How the Body Uses It
Calcium is the primary structural mineral in bones and teeth, stored as hydroxyapatite. It also acts as a signaling ion (Ca²⁺) for muscle contraction, nerve transmission, and hormone release. The body tightly regulates calcium levels through vitamin D, parathyroid hormone (PTH), and calcitonin.
Supplement Origins
Supplemental forms include calcium carbonate (highest concentration), calcium citrate (better absorption in low stomach acid), and microcrystalline hydroxyapatite (MCHA) — a bone-derived matrix providing calcium and phosphorus in a natural ratio.
Possible Uses
- Preventing or correcting low calcium intake, particularly in women and older adults
- Supporting bone density when combined with Vitamin D3 and K2
- Assisting muscle and nerve function in periods of deficiency
Long-Term Use
Safe for long-term use when balanced with magnesium, Vitamin D3, and K2. Excess isolated calcium without cofactors can increase risk of vascular calcification; food-first sources remain best.
Dose Guidance
Studied
Typically 500–1000 mg/day total calcium (from diet + supplements as needed)
Split doses (≤500 mg each) for optimal absorption; carbonate with meals, citrate anytime.
Forms
Calcium carbonate
Standardization: 40% elemental calcium; requires stomach acid for best absorption
Calcium citrate
Standardization: 21% elemental calcium; well absorbed with or without food
Microcrystalline hydroxyapatite (MCHA)
Standardization: Natural bone matrix containing calcium + phosphorus
Delivery
Coming soon.
Evidence & Studies
Maintained bone density in postmenopausal women when combined with Vitamin D3
Reduced fracture risk in older adults with adequate Vitamin D levels
References
Safety & Cautions
Cautions
- Excess supplemental calcium may increase risk of kidney stones
- Use caution in individuals with renal insufficiency
Contraindications
- Hypercalcemia or severe vascular calcification disorders
Interactions
- Interferes with thyroid medications — separate by at least 4 hours
- May reduce absorption of certain antibiotics (tetracyclines, fluoroquinolones)
- Works synergistically with Vitamin D3 and K2 for optimal bone utilization