Calcium is a critical mineral that helps make up your teeth and bones. It is also necessary for muscle contractions, including the proper functioning of the heart. Good food sources of calcium include milk, yogurt, and cheese. Broccoli and green leafy vegetables like kale also have calcium. Sardines and salmon with bones supply calcium. So do calcium-fortified orange juice and cereal. Daily calcium requirements differ due to your age and gender. Some groups of people are at risk for having inadequate calcium levels. Postmenopausal women, vegans, vegetarians, and women who do not have their periods due to anorexia or excessive athleticism may have inadequate calcium levels. Ask your doctor if you should take a calcium supplement. If you take any medications, ask your doctor or pharmacist whether or not calcium supplements interact with anything you are taking.