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Evidence-Based Comparison
Calcium Citrate vs Carbonate: Absorption, Side Effects & Which to Take
Which form of calcium causes less bloating and offers better bioavailability?
Key Takeaway (TL;DR)
Calcium Carbonate provides high elemental calcium (40%) but requires stomach acid and may cause gas/constipation. Calcium Citrate (21% elemental calcium) does not rely on stomach acid, can be taken on an empty stomach, and is gentler on digestion.
Calcium Citrate is best for sensitive stomachs, older adults, and those on acid blockers.
Detailed Comparison
| Criteria | Calcium Citrate | Calcium Carbonate |
|---|---|---|
| Elemental Calcium | ~21% (requires larger pills) | ~40% (smaller pills, higher concentration) |
| Acid Dependence | Acid-independent (absorbs with or without food) | Acid-dependent (must take with meals) |
| GI Side Effects | Low risk of bloating or constipation | Commonly causes gas, belching, constipation |
| Best Candidates | Seniors, PPI users, sensitive digestion | Budget-conscious individuals with normal digestion |
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Includes RDA limits, side effects, and all PubMed trials.
Frequently Asked Questions
Can I take calcium citrate without food?
Yes, calcium citrate is water-soluble and efficiently absorbed whether taken on an empty stomach or with a meal.
Sources:NIH ODS CalciumMayo Clinic Clinical Reviews
This comparison is synthesized from peer-reviewed scientific literature and public health authority guidelines for informational purposes only. Consult a healthcare professional before altering supplementation.