Calcium supplements
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Calcium Supplements: Benefits, Risks, and Efficacy
Calcium Supplements and Bone Mineral Density
Impact on Bone Mineral Density (BMD)
Calcium supplements have been shown to increase bone mineral density (BMD) modestly. A meta-analysis of randomized controlled trials found that calcium supplements increased BMD by 0.7-1.8% at various skeletal sites over one to two years . This increase, however, is small and unlikely to significantly reduce fracture risk . Similarly, calcium supplementation in elderly women prevented seasonal bone loss and increased BMD at the spine and femoral neck .
Calcium and Vitamin D Synergy
Combining calcium with vitamin D has been found to improve BMD more effectively than calcium alone. In a study involving postmenopausal women, calcium plus vitamin D supplementation resulted in a 1.06% higher hip bone density compared to placebo . This combination also maintained parathyroid hormone levels and improved bone density during periods of high physical stress, such as military training .
Cardiovascular Risks Associated with Calcium Supplements
Controversial Findings
The relationship between calcium supplements and cardiovascular disease (CVD) risk is controversial. Some meta-analyses have suggested an increased risk of myocardial infarction and stroke with calcium supplementation Margolis2016Reid2015. However, other high-quality meta-analyses have found no consistent evidence linking calcium supplements to increased cardiovascular events . The evidence remains inconclusive, and further research is needed to clarify these potential risks.
Mechanisms and Recommendations
Potential mechanisms for increased cardiovascular risk include vascular calcification and effects on vascular cells and blood coagulation . Given these concerns, dietary sources of calcium are generally recommended over supplements, as they have not been associated with adverse cardiovascular effects Margolis2016Reid2011.
Calcium Supplements and Other Health Outcomes
Cancer Risk Reduction
Calcium and vitamin D supplementation has been associated with a reduced risk of cancer. A randomized trial found that women taking calcium plus vitamin D had a significantly lower incidence of cancer compared to those taking a placebo . This suggests a potential benefit of these supplements beyond bone health.
Pregnancy and Hypertensive Disorders
Calcium supplementation during pregnancy has been shown to reduce the risk of pre-eclampsia and preterm birth, particularly in women with low dietary calcium intake . High-dose calcium supplementation (≥1 g/day) was associated with a significant reduction in the risk of pre-eclampsia and related maternal and child outcomes .
Conclusion
Calcium supplements can modestly increase bone mineral density and may reduce cancer risk when combined with vitamin D. However, their use is associated with potential cardiovascular risks, and dietary sources of calcium are generally preferred. During pregnancy, calcium supplementation can reduce the risk of hypertensive disorders. Overall, while calcium supplements offer certain health benefits, they should be used cautiously, considering the potential risks and the individual's dietary calcium intake.
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