From the Guidelines
Calcium carbonate is likely to provide adequate calcium supplementation for most people when taken properly, as it is a highly bioavailable source of calcium. It contains 40% elemental calcium, making it one of the highest-concentration calcium supplements available [ 1 ]. For adults needing supplementation, a typical dose is 1000-1200 mg of elemental calcium daily, often divided into 500-600 mg doses for better absorption. To maximize absorption, calcium carbonate should be taken with food since it requires stomach acid for proper dissolution. However, individuals with low stomach acid (such as older adults or those taking acid-reducing medications) may absorb calcium citrate better.
Key Considerations
- Calcium absorption is also dependent on adequate vitamin D levels, so many supplements combine calcium with vitamin D [ 1 ].
- Some people experience mild digestive side effects like constipation or gas with calcium carbonate.
- For those with specific medical conditions like kidney disease or certain medications, the type and amount of calcium supplementation should be discussed with a healthcare provider to ensure it meets individual needs.
- The National Osteoporosis Foundation and American Society for Preventive Cardiology recommend that calcium intake from food and supplements that does not exceed the tolerable upper level of intake (defined by the National Academy of Medicine as 2000 to 2500 mg/d) should be considered safe from a cardiovascular standpoint [ 1 ].
Important Factors
- Balancing cost and bioavailability, calcium carbonate is likely to be the most cost-effective choice in most settings [ 1 ].
- The evidence suggests that there is no significant relationship between calcium supplementation and cardiovascular disease in generally healthy adults [ 1(https://doi.org/10.7326/M15-2400, https://doi.org/10.7326/M16-1743) ].
From the FDA Drug Label
Active ingredient (in each chewable tablet) Calcium carbonate 750 mg The FDA drug label does not answer the question.
From the Research
Calcium Supplementation
- Calcium is necessary for the prevention and treatment of diseases such as osteoporosis, hypertension, and colon cancer 2
- Calcium supplementation can help meet requirements, especially for those who do not meet the adequate intake through their diet 3, 4, 5
Forms of Calcium Supplementation
- Calcium carbonate is a cost-effective form of calcium supplementation, but it should be taken with a meal to ensure optimal absorption 3
- Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or protein-pump inhibitors 3
- Chelated calcium salts are better absorbed in fasting achlorhydric subjects, but have less calcium per gram of supplement 2
Recommended Daily Intake
- The recommended daily intake of calcium varies by age and demographic, ranging from 400 mg/day for infants to 1,500 mg/day for postmenopausal women not on estrogen therapy 4, 5
- Adequate vitamin D is essential for optimal calcium absorption 4, 5
Safety and Risks
- Calcium intake, up to a total intake of 2,000 mg/day, appears to be safe in most individuals 2, 4, 5
- Exceeding 2,000 mg/day of calcium can lead to inadvertent mineral deficiencies and other adverse effects 2
- The risk of advanced and fatal prostate cancer has been associated with calcium intakes from food or supplements in amounts >1500 mg/d 3