From the Guidelines
Calcium carbonate plays a crucial role in maintaining strong bones and teeth, and supporting various bodily functions, including nerve transmission, muscle contraction, and blood clotting, with a recommended daily intake of 500-1200 mg of elemental calcium. When taken as a supplement, calcium carbonate provides elemental calcium that the body absorbs into the bloodstream, contributing to overall health. The body best absorbs calcium carbonate when taken with food, as stomach acid helps break it down 1.
Key Functions of Calcium Carbonate
- Helps maintain strong bones and teeth
- Supports nerve transmission, muscle contraction, and blood clotting
- Functions as an antacid to relieve heartburn, acid indigestion, and upset stomach
- Recommended daily intake: 500-1200 mg of elemental calcium, often divided into smaller doses of 500 mg or less for better absorption
Important Considerations
- Excessive calcium intake can cause constipation, gas, or bloating, and long-term overuse may increase the risk of kidney stones in susceptible individuals 1
- People with certain medical conditions, such as hypercalcemia, kidney disease, or those taking specific medications, should consult healthcare providers before using calcium carbonate supplements 1
- Calcium carbonate is likely to be the most cost-effective choice for calcium supplementation in most settings, although calcium citrate is also a highly bioavailable source 1
Recommendations
- Obtain calcium from food sources whenever possible, and use supplements to correct any shortfalls in intake 1
- Discontinuation of supplemental calcium for safety reasons is not necessary and may be harmful to bone health when intake from food is suboptimal 1
From the Research
Effects of Calcium Carbonate on the Body
- Calcium carbonate is necessary for the prevention and treatment of diseases such as osteoporosis, hypertension, and possibly colon cancer 2.
- It can help meet the adequate intake of calcium, which is often not met by most Americans 3.
- Calcium carbonate should be taken with a meal to ensure optimal absorption, and the maximum dose of elemental calcium that should be taken at a time is 500 mg 3.
- The combination of calcium carbonate with vitamin D is effective in reducing the incidence of non-vertebral and hip fractures, and is often used in the treatment of osteoporosis 4.
Safety and Interactions
- Calcium carbonate can interact with other mineral nutrients and may contain contaminating metals, which has focused attention on safety 2.
- High doses of calcium carbonate can lead to inadvertent mineral deficiencies, and persons at risk for developing milk-alkali syndrome should be identified and monitored for alkalosis and hypercalcemia 2.
- Potential adverse effects of calcium supplementation include gastrointestinal complaints, and renal calculi in most studies have not been associated with calcium supplementation 3.
- The risk of advanced and fatal prostate cancer has been associated with calcium intakes from food or supplements in amounts >1500 mg/d 3.
Comparison with Other Forms of Calcium
- Calcium citrate is better absorbed in fasting achlorhydric subjects, but has less calcium per gram of supplement than calcium carbonate 2.
- 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.
- Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements 3.
Gastric Acid Secretion
- Chronic consumption of calcium carbonate containing antacids over a 3-week-period does not change basal- and meal-stimulated gastric acid secretion in healthy volunteers 5.
- Calcium carbonate is an efficient, inexpensive, and safe antacid, and the evidence for a specific gastric acid rebound with CaCO3 is based upon flawed assumptions and studies 6.