Dairy products, green leafy vegetables and soft-boned fish are all foods naturally high in calcium. Soy and nut milks, tofu, orange juice and breakfast cereal are processed foods commonly enriched with calcium. Calcium is also available as a dietary supplement.
Spinach, collard greens, bok choy and kale are examples of calcium-rich vegetables. While not as high in calcium as leafy greens, figs and oranges are fruits that contain calcium. Sardines and canned salmon are both high in calcium due to the bones consumed with the fish.
Calcium is important for bone and tooth growth in children and maintaining bone strength in adults. Too little calcium can lead to osteoporosis, particularly in older women. Osteoporosis is a disease that causes bones to weaken and become brittle; in severe cases, bones fracture from even minor stresses. This disease is preventable by obtaining sufficient dietary calcium and vitamin D.
Proper absorption of calcium requires vitamin D. Almost all commercially-available milk in the United States is fortified with vitamin D. It is also added to some calcium supplements and calcium-fortified processed foods. Without vitamin D, calcium cannot be absorbed in the digestive system. In the most serious cases, this leads to bone loss, rickets in children and osteoporosis in adults.