Is Calcium safe?
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Is Calcium Safe? A Comprehensive Review
Calcium Intake and Osteoporosis Prevention
Calcium is essential for bone health, and current guidelines recommend a daily intake of 1,000 to 1,300 mg for older adults to prevent osteoporosis and fractures1. Calcium supplementation is particularly useful when dietary intake is insufficient, which is common in North America5 7. However, the safety of calcium supplements has been questioned due to potential adverse effects on cardiovascular health.
Cardiovascular Safety of Calcium Supplements
Conflicting Evidence on Cardiovascular Risk
Recent studies have raised concerns about the cardiovascular safety of calcium supplements. A meta-analysis of randomized controlled trials found that calcium supplements were associated with a 27-31% increased risk of myocardial infarction and a 12-20% increased risk of stroke9. These findings suggest that high levels of calcium intake might be harmful to cardiovascular health, potentially altering public health recommendations1 9.
Expert Panel Recommendations
Contrary to these findings, an expert panel from the National Osteoporosis Foundation and the American Society for Preventive Cardiology concluded that calcium intake, up to the tolerable upper level of 2,000 to 2,500 mg/day, is safe from a cardiovascular perspective2. This conclusion is based on moderate-quality evidence and suggests that calcium, with or without vitamin D, does not increase the risk of cardiovascular disease, cerebrovascular disease, or mortality in generally healthy adults2 3.
Potential Contaminants in Calcium Supplements
Some calcium supplements, particularly those labeled as "oyster shell" or "natural source," have been found to contain significant amounts of lead and aluminum4. While no in vivo toxicity has been reported, chronic use of these supplements may lead to unnecessary metal exposure, raising safety concerns4.
Calcium and Blood Pressure
Calcium supplementation has been shown to have a modest effect on lowering blood pressure in hypertensive individuals. A study found that 1,000 mg/day of calcium significantly reduced systolic and diastolic blood pressure in hypertensive patients, making it a safe and well-tolerated non-pharmacologic intervention for mild to moderate hypertension10.
Calcium and Cancer Risk
The relationship between calcium intake and cancer risk is complex and inconsistent. Some studies suggest that high calcium intake may reduce the risk of breast cancer but slightly increase the risk of prostate cancer8. However, no consistent associations have been found with other types of cancer, and more research is needed to draw definitive conclusions8.
Conclusion
The safety of calcium supplements remains a topic of debate. While some studies suggest an increased risk of cardiovascular events, expert panels and other research indicate that calcium intake within recommended limits is generally safe for healthy adults. Potential contaminants in certain supplements and the modest blood pressure-lowering effects of calcium further complicate the picture. Overall, calcium remains a crucial nutrient for bone health, but individuals should consult healthcare providers to tailor their calcium intake to their specific health needs and conditions.
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Most relevant research papers on this topic
Is Excess Calcium Harmful to Health?
Excess calcium intake may increase the risk of vascular diseases, potentially altering current public health recommendations for preventing osteoporosis.
Systematic Review
Rigorous JournalGuideline: An expert panel found that calcium intake is safe from a cardiovascular perspective
Calcium intake up to the tolerable upper level (2000 to 2500 mg/d) is safe from a cardiovascular perspective in healthy adults.
Rigorous JournalCalcium Intake and Cardiovascular Disease Risk
High calcium intake does not increase cardiovascular disease risk in generally healthy adults, but further high-quality studies are needed to confirm these findings.
Rigorous JournalSafety of some calcium supplements questioned.
Chronic use of calcium supplements may result in unnecessary metal exposure, with lead and aluminum contamination found in some supplements.
Calcium supplementation.
Chelated calcium and refined calcium carbonate tablets are safe and effective for most people, but excessive use may lead to mineral deficiencies.
Highly CitedCalcium
Adequate calcium intake is crucial for maintaining bone health, heart function, nerve transmission, and blood clotting, as well as reducing the risk of osteoporosis, colon polyps, colon cancer, calcium oxalate kidney stones, and hypertension and cholesterol.
Highly CitedCalcium supplementation.
Calcium supplements can be safely and effectively used to prevent osteoporosis and other diseases, but excessive use may lead to mineral deficiencies.
Calcium intake in health maintenance – a systematic review
High calcium intake may slightly improve bone health in children and postmenopausal women, but no consistent evidence links it to cancer, cardiovascular outcomes, or obesity.
Systematic Review
Very Rigorous JournalCardiovascular effects of calcium supplementation
Calcium supplements may increase the risk of cardiovascular disease, with food sources providing similar benefits without these adverse effects.
Meta-AnalysisRigorous JournalHighly CitedBlood pressure response to oral calcium in persons with mild to moderate hypertension. A randomized, double-blind, placebo-controlled, crossover trial.
Oral calcium, 1000 mg/d for 8 weeks, is a safe, well-tolerated, nonpharmacologic intervention that lowers blood pressure in selected patients with mild to moderate hypertension.
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