Phosphorus is an essential macromineral that occurs in all known plant and animal tissues. In adult humans, approximately 85% of all phosphorus occurs in bone. The remaining amount occurs in soft tissue and is essential for normal cellular metabolism. Dietary phosphorus functions primarily to support tissue growth, particularly bone in developing individuals, the formation of cell membranes, numerous specialized proteins such as enzymes and some genetic material, and to replace the normally depleted levels of the mineral in all tissues.

      The current RDI for phosphorus used by the FDA is 1000 mg. The most recent assessment for this nutrient from the National Academy of Sciences (NAS) is detailed in the table below. Because phosphorus is so important in bone development, much higher concentrations of the mineral are required by adolescents, and pregnant and lactating women. Phosphorus is occasionally expressed in grams, where 1 gram = 1000 mg (milligrams).

      Unlike calcium, the absorption of phosphorus does not vary with dietary intake. In other words, the total amount of phosphorus actually absorbed by the body is not affected by the type or amount of other dietary constituents.
      Phosphorus is a naturally occurring compound in nearly all plant and animal tissues. Some of the best dietary sources for this mineral are milk and other dairy products, various meats, beverages such as cola and cola-like drinks, and other fortified food products.

      Inadequate intake of dietary phosphorus (hypophosphatemia) is quite uncommon among individuals who maintain a reasonable diet. It has been estimated that near total starvation would be required in an otherwise healthy individual to produce the effects of severely depleted phosphorus (phosphate) concentrations.
      Certain diseases, such as diabetic ketoacidosis, can significantly reduce phosphorus levels, but generally present other, more serious problems before phosphorus depletion can become an issue. Individuals who consume very large amounts of aluminum-containing antacids (e.g., DiGel, Gelusil, Maalox, Mylanta, and Rolaids, among others), or use these products over long periods of time, should be aware that these substances also have the ability to significantly reduce phosphorus levels, as well as increase calcium excretion in the urine, thereby reducing the levels of that mineral as well (see Calcium Deficiencies).
      The effects of hypophosphatemia, should they occur, have included loss of appetite (anorexia), muscle weakness, various bone disorders, anemia, susceptibility to infection, and general debility. Prolonged depletion can lead to much more serious disorders, and ultimately death.

      Phosphorus supplements are not commonly used in most developed areas of the world because of the wide availability of the mineral from normal dietary sources. Even multivitamins typically do not contain phosphorus, and when they do, the amount of the mineral is relatively small.

      Excessive intake of phosphorus from any source (hyperphosphatemia), though typically not from dietary sources alone, can cause a number of problems, primarily involving calcium metabolism. Other, peripheral imbalances resulting from excessive phosphorus levels, such as hormone regulation, have also been seen to disrupt calcium metabolism and, particularly in developing individuals, problems with bone development. In the most severe cases, calcium imbalances may lead to calcification of soft tissues (metastatic calcification). Although demonstrated in laboratory animals and relatively uncommon in humans, when this occurs in critical organs, such as the kidney, life threatening disorders are possible.
      Some reports, though inconsistent, have suggested that excessive levels of phosphorus may interfere with the absorption of iron, copper and zinc. Individuals who may have depleted levels of such trace minerals for other reasons, should at least be aware of this potential and monitor their diets for items containing high levels of phosphorus such as colas, cola-like beverages, and food products fortified with phosphorus. In this regard, excessive intake of Vitamin D can also increase phosphorus absorption, a fact that should be considered when evaluating the overall diet.
      In light of potential health risks, and the levels at which they may occur, the most recent National Academy of Sciences (NAS) study on Dietary Reference Intakes (see Reference Values for Phosphorus table above) has recommended a tolerable upper intake level (UL) for adults of 4000 mg/day for phosphorus.