Calcium
TL;DR
Most abundant mineral in the body; essential for bones and heart rhythm
Low evidence for preventing heart disease; some concern it may worsen it
Low evidence for kidney health
Food sources are much safer than supplements for heart health
Generally safe but can cause constipation and kidney stones
Very cheap: ~$5-10/month
Best for: Bone density (only if dietary intake is low)
What it is
Calcium is famous for bones, but it's also a critical 'electrolyte' that tells your heart to beat and your muscles to contract. The body keeps blood calcium levels in a very tight range—if you don't eat enough, the body 'steals' it from your bones.
However, 'more' is not better. In the last decade, evidence has emerged that large doses of supplemental calcium can lead to 'spikes' in blood calcium that promote arterial calcification. This has made calcium one of the most controversial supplements for heart health.
What the research says
Calcium's heart relationship is complicated. The Risk. Large meta-analyses have suggested that calcium supplements (but not dietary calcium) may increase the risk of heart attacks. Why? It is thought that a large 'bolus' of calcium from a pill causes a temporary hypercalcemic state that promotes plaque formation. Verdict. Unless directed by a doctor for osteoporosis, it's better to get your calcium from yogurt, sardines, and greens.
Calcium is a double-edged sword for the kidneys. Benefit. Taking calcium with meals can bind to oxalates, preventing kidney stones. Risk. However, taking calcium supplements between meals can increase the amount of calcium in the urine, potentially increasing stone risk. It is not a recommended treatment for kidney disease.
Calcium on Amazon
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Safety
Generally safe, but common side effects include constipation and bloating. High doses increase the risk of kidney stones. Always take with Vitamin D and K2 to minimize vascular risks.
Interactions
- Thyroid Meds: Reduces absorption of Levothyroxine; separate by 4 hours.
- Antibiotics: Reduces absorption of Tetracyclines and Quinolones.
- Bisphosphonates: Interferes with absorption.
Dosing
Standard Dose: 500-1,000 mg daily, but only as needed to reach a total of 1,200mg from all sources. Form: Calcium Citrate is better absorbed and easier on the stomach than Calcium Carbonate.
Cost
Dirt cheap. $5-10 per month.
The bottom line
Calcium is a supplement you should probably stop taking unless you have a specific medical reason for it. Focus on food first; the heart-health risks of pills are real.
Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.
This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.