From the Guidelines
Calcium carbonate contains 40% elemental calcium by weight, meaning that for every 100 mg of calcium carbonate, you get 40 mg of elemental calcium. This is a crucial factor to consider when taking calcium supplements, as the dosage is typically expressed in terms of elemental calcium rather than the total weight of the compound. For instance, a 1000 mg calcium carbonate supplement actually provides about 400 mg of elemental calcium 1.
Importance of Elemental Calcium Content
The high percentage of elemental calcium in calcium carbonate is due to its molecular structure (CaCO₃), where the calcium atom makes up a significant portion of the molecule's mass compared to the carbonate component. This makes calcium carbonate one of the most concentrated forms of calcium supplementation available, which is why it's commonly used in over-the-counter supplements 1.
Comparison with Other Calcium Supplements
In comparison, other calcium supplements like calcium citrate provide less elemental calcium, with about 21% elemental calcium content 1. Calcium gluconate and calcium lactate have even lower elemental calcium content, at 9% and 13%, respectively 1.
Clinical Implications
Understanding the elemental calcium content in calcium supplements is essential for ensuring that patients receive the appropriate dosage to meet their daily calcium requirements. This is particularly important for individuals with inadequate dietary calcium intake or those at risk of calcium deficiency 1.
Recommendations
When prescribing or recommending calcium supplements, it is essential to consider the elemental calcium content to ensure the patient receives the correct dosage. For example, if a patient requires 1000 mg of elemental calcium per day, they would need to take 2500 mg of calcium carbonate to achieve this, given its 40% elemental calcium content 1.
From the FDA Drug Label
Each chewable tablet contains: calcium 300 mg Active ingredient (in each chewable tablet) Calcium carbonate 750 mg The amount of elemental calcium in calcium carbonate can be calculated using the formula:
- Calcium carbonate (CaCO3) contains 40% elemental calcium by weight
- For a 750 mg calcium carbonate tablet, the elemental calcium content would be 40% of 750 mg, which is 300 mg This is consistent with the information provided in the drug label 2. Therefore, the elemental calcium content in calcium carbonate is 40% of the calcium carbonate weight, or 300 mg for a 750 mg calcium carbonate tablet 2.
From the Research
Calcium Content in Calcium Carbonate
- The elemental calcium content in calcium carbonate is not explicitly stated in the provided studies 3, 4, 5, 6, 7.
- However, it is known that calcium carbonate is a compound containing calcium, carbon, and oxygen, with the chemical formula CaCO3.
- The calcium content in calcium carbonate can be calculated based on its molecular weight, but this information is not provided in the given studies.
Bioavailability of Calcium from Calcium Carbonate
- Studies have compared the bioavailability of calcium from calcium carbonate with other calcium salts, such as calcium citrate 4, 5, 6, 7.
- The bioavailability of calcium from calcium carbonate has been found to be lower than that of calcium citrate in some studies 5, 7.
- However, one study found that calcium from calcium carbonate is fully as absorbable as from calcium citrate when taken with food 4.
Comparison with Other Calcium Salts
- Calcium citrate has been found to have higher bioavailability than calcium carbonate in some studies 5, 7.
- Calcium formate has been found to have higher bioavailability than both calcium carbonate and calcium citrate in one study 6.
- The differences in bioavailability between calcium salts may be influenced by factors such as solubility, ionization, and the presence of food 4, 5.