Calcium helps build strong bones and teeth while preventing high cholesterol, tooth decay, and muscle cramps. Your heart, muscles, and nerves also need calcium to function properly.   Vitamin D and calcium, when taken together, help protect our bones. Vitamin D is needed for the body to absorb calcium in the gut and is also necessary for the regulation of calcium levels in the blood. Without vitamin D, a calcium deficiency is possible. Foods high in calcium are dairy products, sardines, canned fish, almonds, and leafy green vegetables. Although diet is the best way to get calcium, calcium supplements may be an option if your diet falls short.