Calcium

Calcium plays a vital role in the anatomy, physiology and biochemistry of organisms and of the cell, particularly in signal transduction pathways. More than 500 human proteins are known to bind or transport calcium. The skeleton acts as a major mineral storage site for the element and releases Ca2+ ions into the bloodstream under controlled conditions. Circulating calcium is either in the free, ionized form or bound to blood proteins such as serum albumin. Parathyroid hormone (secreted from the parathyroid gland) regulates the resorption of Ca2+ from bone. Calcitonin stimulates incorporation of calcium in bone, although this process is largely independent of calcitonin. Although calcium flow to and from the bone is neutral, about 5 mmol is turned over a day. Bone serves as an important storage point for calcium, as it contains 99% of the total body calcium. Low calcium intake may also be a risk factor in the development of osteoporosis. The best-absorbed form of calcium from a pill is a calcium salt like carbonate or phosphate. Calcium gluconate and calcium lactate are absorbed well by pregnant women. Seniors absorb calcium lactate, gluconate and citrate better unless they take their calcium supplement with a full breakfast. The currently recommended calcium intake is 1,500 milligrams per day for women not taking estrogen and 800 milligrams per day for women on estrogen. There is close to 300 milligrams of calcium in one cup of fluid milk. Calcium carbonate is currently the best and least expensive form of calcium supplement available.