From the Guidelines
Calcium supplements can cause minor side effects, including constipation and dyspepsia, and may increase the risk of nephrolithiasis in a dose-dependent manner.
Common Side Effects
- Minor constipation
- Dyspepsia
Less Common Side Effects
- Nephrolithiasis (kidney stones), with a relative risk of 1.17, as seen in the WHI trial 1
Cardiovascular Risks
The evidence suggesting adverse cardiovascular effects of calcium supplementation is inconsistent, and an accepted biologic explanation is lacking 1. However, some studies have raised concerns about a possible increase in cardiovascular risk associated with calcium supplementation, with a meta-analysis showing an increased risk of myocardial infarction among persons randomly assigned to calcium (odds ratio, 1.27; 95% CI, 1.01 to 1.59) 1.
Safe Intake Levels
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.
Recommendations
The National Osteoporosis Foundation and American Society for Preventive Cardiology recommend that calcium with or without vitamin D intake from food or supplements has no relationship (beneficial or harmful) to the risk for cardiovascular and cerebrovascular disease, mortality, or all-cause mortality in generally healthy adults at this time 1.
The FDA Drug Labels for calcium (PO) do not address this question.
From the Research
Side Effects of Calcium Supplements
The potential side effects of calcium supplements include:
- Gastrointestinal complaints, such as constipation 2, 3
- Kidney stones, with a 17% increase in risk 4
- Increased risk of cardiovascular diseases, including myocardial infarction, with a 20-40% increase in risk 5, 6, 4
- Potential adverse effects on vascular disease, which may increase mortality 6
- Gastrointestinal side effects, including a doubling of hospital admissions for these problems 4
Specific Risks
Certain populations may be at higher risk for side effects from calcium supplements, including:
- Community-dwelling adults with high calcium intake, who may be at increased risk for cardiovascular diseases 5
- Individuals with achlorhydria or those taking histamine-2 blockers or protein-pump inhibitors, who may need to take calcium citrate instead of calcium carbonate 2
- Men with high calcium intake, who may be at increased risk for advanced and fatal prostate cancer 2
Important Considerations
When taking calcium supplements, it is essential to consider the following:
- The maximum dose of elemental calcium that should be taken at a time is 500 mg 2
- Calcium supplements should be prescribed and taken cautiously, accounting for individual patients' risks and benefits 5
- Current evidence does not support the use of calcium supplements in healthy community-dwelling adults 3