Phosphorus, the element in the periodic table, with the symbol P, is the second most abundant mineral, after calcium, in the human body. Approximately 85% of the 700 grams in the average adult body can be found in the skeleton and teeth in the form of calcium phosphate crystals. The remaining 15% is distributed to both every cell in the body and extracellular fluid.
A normal serum level of phosphorus is maintained at 2.4-4.1 mg/dL in most adults. However, older adults are more prone to have lower levels.
The phosphorus serum levels are regulated by the parathyroid hormone (PTH) and Vitamin D (calcitriol) in the small intestine and bones. A level of below 2.4 mg/dL is diagnosed as hypophosphatemia, the medical term for a low blood level concentration of phosphorus.
Phosphorus deficiency usually occurs as the result of a serious medical condition and very rarely as the result of diet alone. The average American diet contains plenty of phosphorus, probably too much. However, ordinarily, the body is very adept at adjusting to a higher than optimal phosphorus intake, so there is no long term damage. Problems are more apt to occur on a long term diet that is very high in phosphorus but low in calcium.