Calcium Content of Blood A normal ionized calcium content is essential for normal calcification of bone. A decrease in the ionized calcium content to below 3 mg is called Hypocalcaemia and this will lead to the development of tetany. In tetany, the motor nerves become over susceptible to stimuli. This particularly affects the face, hands and feet, producing the clinical features of tetany. Muscles lose tone and become flabby.
An increase in ionized calcium content to over 10 mg. may cause renal failure and cardiac arrest.
Calcium Balance Dietary calcium, which is not absorbed in the intestines is excreted in the faeces. A small part of the absorbed calcium is excreted in urine. Calcium balance, i.e., the difference between the quantity of calcium ingested and that excreted in urine and faeces is positive during growth, pregnancy, lactation and in normal adults. The excretion of calcium continues on a calcium deficient diet when the body will be in negative calcium balance.
Calcium: Phosphorus Ratio in the Diet During rapid growth and calcification, the diet should have calcium and phosphorus in the ratio of 1:1. When the calcium is required only for maintenance as in adults, the calcium requirement is lower, both absolutely and relatively to the phosphorus requirement. Thus, the calcium: phosphorus ratio is highest at the earlier age (1:1), decreases with the attainment of adult status (1:2), and then, in the case of the female increases again (1:1) in the latter part of pregnancy and during lactation. In the normal adult the calcium: phosphorus ratio of the whole body is a little under 1:1 and that of the bone is a little over 2:1.