Calcium is often added to foods to provide this much needed mineral, required mainly for good bone development and your teeth. Calcium in an adult is 1 - 1.4 kg of body weight, so is a vital element for human biology. Most calcium is found in bones and teeth, predominantly calcium phosphate. The much smaller amounts of calcium found in blood plasma and tissues are needed in the proper functioning of your nervous system, muscle contraction, blood clotting and other metabolic processes.
An adult needs about 500 mg each day, whereas pregnant and breastfeeding women need about 1,200 mg each day. Both amounts are quite a lot for a mineral. To get calcium to be adequately absorbed into the body, you also need vitamin D, with lack of either potentially causing calcium deficiency. Vitamin D works with parathyroid hormone to keep calcium in the blood plasma within the correct range for proper functioning of metabolic processes. A lack of either calcium or vitamin D can result in osteoporosis or rickets.
Most of our calcium comes from grains and cereals, dairy, fish, especially if the bones are eaten and vegetables. The richest natural sources of dietary calcium are in cheese and milk, but not cream, cream cheese and butter, where fats are more concentrated. Other sources of calcium include: cauliflower, broccoli, cabbage, haggis, sardines, spinach and tripe.
Calcium may also be added to foods as calcium salts - calcium carbonate (or chalk) or calcium phosphate, for example, are added back to bread. Calcium carbonate is a white odourless and tasteless substance that is insoluble in plain water, but soluble in acidic water.
Calcium carbonate is the "fur" that clogs up kettles and pipes in hard water areas. Calcium carbonate is added to plain white flour to return some of the lost minerals from the industrial milling process. Calcium salts, e.g calcium carbonate or calcium phosphate are added to vegetable "milk" drinks to mimic the calcium that you would get in a cow's milk.