Calcium is the most abundant mineral in your body. It is essential for the development and maintenance of strong bones and teeth, and that’s where about 99% of the body's calcium is found. Calcium also helps the heart, nerves, muscles, and other body systems work properly. It is probably best known for helping prevent osteoporosis. Your body needs several other nutrients in order for calcium to be absorbed and used properly, including magnesium, phosphorous, and especially vitamins D and K. The best way to get calcium is through food (see "Dietary Sources" section). Many foods are fortified with calcium, but some people may still need to take calcium supplements to get enough. It is especially important for children to get enough calcium in their diet as they are growing and forming bone, and for older people as they start to lose bone.
People who consume large amounts of caffeine, alcohol, or soda, and those who take corticosteroid medications may need calcium supplements. Calcium deficiency can be found in people who don’t absorb enough calcium, as can happen with Crohn's disease, celiac disease, and some intestinal surgeries.