Phosphorus

The abundant supply of phosphorus in foods almost precludes the possibility of dietary deficiency occurring in man. The daily allowance should probably be about equal to that of calcium for children and for women during pregnancy, perhaps 1.5 times that of calcium for other adults (4a). Phosphorus is distributed in the body as follows: about 80 per cent in bones and teeth, 10 per cent in combination with proteins, lipids, carbohydrates and other organic compounds in muscles, and the remainder throughout the body in organic combination (63). The deposition and release of phosphorus from bones is de-pendent on the same mechanisms that affect calcium.

Phosphorus has a vital role in many metabolic processes; phosphorus compounds are essential in fat and carbohydrate metabolism and are involved in muscle contraction and in energy transfer systems. Phosphorylation is essential for absorption of certain nutrients. Phosphates of extracellular fluid participate in acid base regulation and phosphate is the chief inorganic ion of intracellular fluid. The normal inorganic phosphate concentration in blood is 2 to 4.5 mg/100 ml (1.2-3.0 mEq/1) in adults, 3 to 5 mg/100 ml (2.5-4.5 mEq/1) in children.

Phosphorus metabolism, like that of calcium, is disturbed in rickets, osteomalacia and diseases of the thyroid and parathyroid glands. The metabolism of this mineral is also influenced by the steroid hormones. In rickets, urinary excretion of phosphorus is increased. This also occurs in the Fanconi syndrome apparently due to a renal lesion which prevents reabsorption of phosphorus from the tubules (p. 42). In “resistant rickets,” studies with radioactive phosphorus have shown phosphorus absorption to be normal. Mechanisms responsible for this syndrome have not been determined; endocrine imbalance, abnormal renal function or metabolic abnormalities have been suggested.