From the Guidelines
Calcium carbonate is more constipating than calcium citrate due to its requirement for stomach acid for proper absorption, which can slow down bowel movements. This is supported by studies such as 1, which notes that calcium carbonate is more likely to cause constipation and bloating, and should be taken with meals to aid in absorption. In contrast, calcium citrate provides less elemental calcium but is a reasonable alternative for patients with gastrointestinal symptoms, as it can be taken with or without meals and is less likely to cause constipation 1.
To minimize constipation when taking calcium supplements, it is recommended to:
- Stay well-hydrated
- Maintain adequate fiber intake
- Split calcium doses throughout the day rather than taking it all at once
- Consider taking calcium citrate instead of calcium carbonate, especially if experiencing constipation or having low stomach acid
The typical daily dosage for calcium supplements ranges from 500-1000mg, depending on dietary intake and specific health needs, with calcium carbonate providing 40% elemental calcium content and calcium citrate providing 21% elemental calcium content 1.
From the Research
Calcium Supplementation Forms
- Calcium carbonate and calcium citrate are the most common forms of calcium supplements 2
- Calcium carbonate is the most cost-effective form, but should be taken with a meal to ensure optimal absorption 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 2
Constipation and Calcium Supplementation
- There is no direct evidence in the provided studies to suggest that calcium carbonate is more constipating than calcium citrate or vice versa
- However, a study on fiber supplementation found that increasing fiber intake can improve symptoms of chronic constipation, but it did not specifically address the effect of calcium supplementation on constipation 3