category: nutrition science: nutrients

Phosphorus, phosphate, de.: Phosphor, Phosphat

Phosphorus (chemical symbol: P) is a mineral and bulk element. A phosphate is a salt or ester of phosphoric acid. The mineral phosphorus is essential for the human organism.

Sources of Phosphorus

Phosphates are contained in almost all foods. Proteinrich foods such as milk, meat, fish and eggs contain high amounts of phosphates. Polyphosphates (linear connected, condensed phosphates) are used as food additives in the food industry. They are needed to soften water, as emulsifying salt for processed cheese or for the preparation of cooked sausages, surimi or fish fingers. In Cola soft drinks the amount of phosphates (as phosphoric acid) are also very high.

Functions of Phosphorus

Phosphorus is an element of many important molecules within the organism (e.g. ATP and DNA). As phosphoric acid phosphorus has important functions in intermediate metabolism of all cells within the human body. Conversion, utilization and storage of energy is achieved through decomposition and synthesis of adenosine triphosphate (ATP). For propagation of genetic information phosphorus in form of nucleic acids (DNA) plays an important role. Furthermore phosphorus ensures a stable pH-value (acid-base level) of the blood. It acts as a buffer and regulates the pH-value. In combination with calcium phosphorus works as a stabiliser in bones, which is where we find the largest part of our phosphorus.

Phosphorus and metabolism

Organic phosphorus compounds in form of phosphates taken in via our food are processed to inorganic phosphates with the help of enzymes. In the small intestines up to 70 % of the consumed mineral are resorbed and go into the blood stream. Excretion of phosphates is done via the kidneys (60 - 80 %) and faeces (20 - 40 %). A small part of phosphorus is excreted through sweating.

Phosphorus forms insoluble salts with iron, aluminium and calcium. Resorption of phosphorus can therefore be hindered through a simultaneous high intake of these minerals.

Phosphates from cereals are available in form of phytic acid. It is only bioavailable for humans if the phosphorus is separated from the phytate molecules by phytase, an enzyme also contained in cereals. Phytates are activated (1.) during germination of the cereals (see also: cereal germ), (2.) in sour dough and (3.) depending on the dough environment.

Phosphorus requirements

The necessary amount of phosphorus depends on the calcium intake. Both minerals should be consumed in a 1:1 to 1:1,2 (Calcium : Phosphorus) ratio. With the common balanced diet most people consume more phosphate than calcium. Even with a vegetarian diet the recommended ratio of 1:1 or 1:1,2 is not always achieved. Foods from animal sources contain large amounts of phosphate and, with the exception of milk and milk products, only small amounts of calcium. Therefore it is easier to achieve the recommended ratio of phosphorus and calcium with a vegetarian diet.