Most phosphate (about 80 per cent) is stored in the bones, interacting and interrelated with calcium as hydroxyapatite.
A small fraction of phosphate, 1 per cent is in the blood mainly as inorganic phosphate and phospholipids. The rest is found within cells throughout the body, where it is mainly used to store energy.
This small blood fraction of phosphate is very important. It is controlled control by Parathyroid hormone, vitamin D and fibroblast growth factor 23 (FGF23).
Humans get dietary phosphate via the small intestine utilising pathways that may involve vitamin D, and FGF23 mobilises phosphate from bone, to maintain plasma phosphate levels for energy use.
Some vegans and vegetarians may be phosphate deficient. Only about 50% of the phosphate in plant sources such as beans, lentils, grains, peanuts and almonds is available to the body because we lack the enzymes to process it. An exception to that is yeasty bread because yeast provides the necessary enzyme.
In the body, phosphorus is combined with oxygen to form a variety of phosphates (PO4). Phosphates are vital for energy production, muscle and nerve function, and bone growth. They also play an important role as a buffer, helping to maintain the body’s acid-base balance.
Most phosphate in the body comes from dietary sources. A variety of foods, such as beans, peas and nuts, cereals, dairy products, eggs, beef, chicken and fish contain small amounts of phosphate.
Low levels of phosphate may indicate abnormally high levels of calcium, effects of diuretics (drugs that encourage urination), burns, diabetic ketoacidosis after treatment, habitual use of antacids – medications for heartburn, rickets and osteomalacia (due to Vitamin D deficiencies).
High levels of phosphate may be related to Kidney failure, Hypoparathyroidism (underactive parathyroid gland), Hypocalcaemia (abnormally low levels of calcium), Diabetic ketoacidosis when first seen, Phosphate supplementation.