Relationship between calcium supplements and cardiovascular disease

Calcium supplements increase bone density and are frequently prescribed to patients with osteoporosis. However, it is not certain whether they reduce the risk of fracture. A recent study from Auckland, New Zealand raised the possibility that calcium supplements might increase the risk of a heart attack (1). Therefore the medical community is reassessing the pros and cons of taking calcium supplements. After taking calcium tablets, the concentration of calcium in blood increases slightly for a few hours. The flow of calcium from blood into the muscle cells that line blood vessels causes them to contract. We hypothesize that the increase in blood calcium after taking calcium tablets makes the blood vessels contract and become stiffer, putting pressure on the heart. This study will assess the stiffness of blood vessels in 20 subjects before and after a single dose of calcium. We hope to determine whether arterial stiffening is a mechanism that could explain a relationship between calcium supplements and an increased risk of heart disease. Reference 1. Bolland MJ, Barber PA, Doughty RN et al. BMJ 2008; 336:262-266