Calcium is a mineral most often associated with healthy bones and teeth, although it also plays an important role in blood clotting, helping muscles to contract, and regulating normal heart rhythms and nerve functions. About 99% of the body’s calcium is stored in bones, and the remaining 1% is found in blood, muscle, and other tissues.
Several literature reviews on the topic of total calcium intake, from food and supplements, and blood pressure have suggested a possible link to lowering high blood pressure.
Some research has raised concerns about calcium supplements and heart health. These studies found that taking calcium supplements increased the risk of cardiovascular events in men and women. It has been suggested that high-dose supplements can cause hypercalcemia (toxic level of calcium in the blood) that can cause blood to clot or the arteries to harden, leading to cardiovascular disease.
Calcium is one of the most important nutrients required for bone health. Bone is living tissue that is always in flux. Throughout the lifespan, bones are constantly being broken down and built up in a process known as remodeling. Bone cells called osteoblasts build bone, while other bone cells called osteoclasts break down bone if calcium is needed. In healthy individuals who get enough calcium and physical activity, bone production exceeds bone destruction up to about age 30. After that, destruction typically exceeds production. This is sometimes called “negative calcium balance,” which can lead to bone loss. Women tend to experience greater bone loss than men later in life due to menopause, a condition that lowers the amount of hormones that help to build and preserve bone.
Epidemiological studies following people over time suggest a protective role of high calcium intakes (whether from food and/or supplements) from colorectal cancer.
At one time, experts recommended that people with kidney stones limit their calcium intake because the mineral makes up one of the most common types of stones, called calcium-oxalate stones. What we know now is the reverse—that not eating enough calcium-rich foods can increase the risk of stone formation. Research from large trials including the Women’s Health Initiative and the Nurses’ Health Study found that a high intake of calcium foods decreased the risk for kidney stones in women.