MineralsStrong Evidence3rd Party Tested

Calcium

Also known as: Calcium Carbonate, Calcium Citrate, Calcium Gluconate

The most abundant mineral in the body, essential for bone, muscle, and nerve function

9/10 Evidence Score

Primary Benefit

Bone Density and Structural Integrity

Standard Dose

1,000 to 1,200 mg/day (through diet and supplementation combined)

Evidence

Certifications

USP VerifiedNSF Certified

Overview

Calcium is the most abundant mineral in the human body, with 99% stored in bones and teeth. Beyond structural roles, calcium is essential for muscle contraction, nerve signal transmission, blood clotting, and enzyme activation. Chronic inadequate intake accelerates osteoporosis, particularly in post-menopausal women. Calcium citrate is better absorbed on an empty stomach, while calcium carbonate requires stomach acid.

Benefits & Evidence

Essential component of hydroxyapatite crystal in bone matrix
Required for muscle contraction including heart muscle
Mediates neurotransmitter release and nerve function
Involved in blood clotting cascade
May reduce colorectal cancer risk with adequate intake

Clinical Study Summaries

Calcium plus vitamin D supplementation and the risk of fractures

2006

New England Journal of Medicine

The Women's Health Initiative found calcium plus vitamin D supplementation modestly increased hip bone density but did not significantly reduce fracture risk in community-dwelling women, with increased kidney stone risk.

View study

Recommended Dosage

Standard Dose	1,000 to 1,200 mg/day (through diet and supplementation combined)
Minimum	1,000 mg/day (adults 19 to 50)
Maximum	2,500 mg/day (UL); above 1,500 mg/day associated with risks
Timing	Split into doses of 500 mg or less for best absorption

Notes: Calcium carbonate is cheapest and highest elemental calcium but requires stomach acid. Calcium citrate is better for those with low stomach acid or taking PPIs. Always prioritize dietary calcium from dairy, leafy greens, and fortified foods over supplements.

Side Effects & Interactions

Potential Side Effects

Constipation (especially calcium carbonate)
Kidney stones with very high intake in susceptible individuals
Cardiovascular risk concerns at high supplemental doses (evidence debated)
Bloating and gas

Drug & Nutrient Interactions

Iron (impairs absorption, take separately)
Zinc (high calcium impairs zinc absorption)
Thyroid medications (calcium impairs levothyroxine absorption, separate by 4 hours)
Bisphosphonates (calcium impairs absorption, take separately)