Calcium (Ca)

Blood calcium concentration is closely regulated by intake control at the bowel wall, active deposits and withdrawals from bone, and close monitoring of the amount the kidney excretes. Calcium absorption from GI tract is regulated by vitamin D and parathyroid hormones. Without parathormone, you cannot actively transport calcium through GI tract. Each mineral works best in proportion to other minerals. Vitamin D  and calcium intake recommendations must therefore take into account the kind of calcium, the amount of vitamin D in the diet, the amount of sun exposure, the activity of parathormone, the dietary intake of binding substances like Phytic acid, and competition of calcium with phosphorus, magnesium and other minerals.

If blood calcium drops even marginally, a state of nervous and muscular hyperactivity - tetany - quickly appears. You can induce tetany in a few minutes by hyperventilating. The increased gas exchange in the lung lowers blood carbon dioxide (as dissolved bicarbonate), raises the blood pH, lowers the calcium concentration, and you are shaky, anxious, with hand muscle cramps drawing your fingers into a clenched fist. You may wake up at night after hyperventilating in your sleep with cramps and muscle spasm from abruptly falling serum calcium concentration. Taking extra calcium may not correct the tetany of hyperventilation (especially at night) because the blood pH change is a sudden and powerful controller of calcium concentration, and oral intake of calcium the previous day is not. The solution for hyperventilation tetany is to rebreathe in a paper bag, since this causes rapid re-accumulation of blood carbon dioxide, normalization of the pH and calcium concentration.

Bone stores 99% of body calcium and calcium salts, laid down in a soft protein matrix , are responsible for the hardness of bones. Long-term calcium deficiency leads to bone thinning or osteomalacia. Osteomalacia refers to the reduction of the mineralization of bone. The problem of demineralization of bone is confused with loss of whole bone tissue (osteoporosis.)

 

A high calcium intake and adequate Vitamin D will promote optimal bone mineralization in youth and decrease the rate of bone-mineral loss in the later postmenopausal period. Lack of Vitamin D in children leads to Rickets -soft, poorly mineralized bone that bends easily. In older women, a high plasma level of vitamin D enhances calcium absorption, whereas high sodium, protein, alcohol and caffeine intakes will cause increased urinary losses and negative calcium balance. Other regulatory changes and/or vitamin D deficiency may alter the balance between calcium absorption from the bowel and excretion from the kidney. 

 

The term "Osteoporosis" refers to a loss of total bone mass and not just bone thinning due to calcium deficiency. Bone loss in adults increases the risk of bone fractures and may contribute to the loss of teeth in healthy postmenopausal women. Low bone mass in women is attributed to heredity, estrogen deficiency and lack of regular physical activity.