Calcium Carbonate vs. Calcium Citrate
Among 5,062 on-market calcium products with an identifiable primary form, 47.2% use Calcium Carbonate (2,391 products) and 20.3% use Calcium Citrate (1,027).
| Calcium Carbonate | Calcium Citrate | |
|---|---|---|
| Quality tier | Tier 2 | Tier 1 |
| Calcium by weight | 40.0% | 21.1% |
| Share of market | 47.2% | 20.3% |
| On-market products | 2,391 | 1,027 |
| Median declared dose | 130 elemental mg middle half: 50–300 | 125 elemental mg middle half: 50–400 |
| Most common brands | Wonder Laboratories, DC, 21st Century | Bluebonnet, Pure Encapsulations, Bariatric Advantage |
Doses are declared per serving in elemental mg. “By weight” is the share of the ingredient that is the nutrient itself (e.g. elemental magnesium in a magnesium salt).
Why Calcium Carbonate is tier 2
Absorption from calcium citrate was 20-27% higher than from carbonate in a meta-analysis (15 studies, 184 subjects; Sakhaee 1999), i.e. carbonate absorbed roughly 17-21% less; carbonate absorption is better with meals/gastric acid (general pharmacology, not from the abstract).
Source: Sakhaee K et al. 1999, Am J Ther 6(6):313-321, PMID 11329115
Why Calcium Citrate is tier 1
Meta-analysis of 15 studies (184 subjects): absorption significantly higher than carbonate by ~20-27% (27.2% fasting, 21.6% with meals). Citrate absorption is generally considered less dependent on gastric acid (general pharmacology, not from the abstract).
Source: Sakhaee K et al. 1999, PMID 11329115