Phosphorus was discovered in 1669 by Hennig Brand, who prepared it from urine. Not less than 50-60 buckets per experiment in fact, each of which required more than a fortnight to complete. The origin of the name is from the Greek word "phosphoros" meaning "bringer of light" (an ancient name for the planet Venus?).

Phosphorus is commonly misspelled "phosphorous". It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several allotropic forms including white (or yellow), red, and black (or violet). White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is colourless and transparent. It is insoluble in water, but soluble in carbon disulphide. It catches fire spontaneously in air, burning to P₄O₁₀, often misnamed as phosphorus pentoxide. When exposed to sunlight, or when heated in its own vapour to 250°C, it is converted to the red variety. This form does not ignite spontaneously and it is a little less dangerous than white phosphorus. The red modification is fairly stable and sublimes with a vapour pressure of 1 atmosphere at 417°C.

Phosphorus, the second most abundant element (after calcium) present in our bodies, makes up about 1 percent of our total body weight. It is present in every cell, but 85 percent of the phosphorus is found in the bones and teeth. In the bones, phosphorus is present in the phosphate form as the bone salt calcium phosphate in an amount about half that of the total calcium. Both these important minerals are in constant turnover, even in the bone structure.

Phosphorus is very involved with bone and teeth formation as well as most metabolic actions in the body, including kidney functioning, cell growth and the contraction of the heart muscle. The main inorganic component of bone is calcium phosphate salts while cell membranes are composed largely of phospholipids. While it assists the body in vitamin use (especially some B group vitamins), it also is involved in converting food to energy.

Phosphorus is involved in many functions besides forming bones and teeth. Like calcium, it is found in all cells and is involved in some way in most biochemical reactions. Phosphorus is vital to energy production and exchange in a variety of ways. It provides the phosphate in adenosine triphosphate (ATP), which is the high-energy carrier molecule in the body's primary metabolic cycles. Phosphorus is important to the utilization of carbohydrates and fats for energy production and also in protein synthesis for the growth, maintenance, and repair of all tissues and cells. As inorganic phosphate in ATP, it is needed in protein synthesis and in the production of the nucleic acids in DNA and RNA, which carry the genetic code for all cells.

Phosphorus also helps in kidney function and acts as a buffer for acid-base balance in the body. Phosphorus aids muscle contraction, including the regularity of the heartbeat, and is also supportive of proper nerve conduction. This important mineral supports the conversion of niacin and riboflavin to their active coenzyme forms. As mentioned, parathyroid hormone regulates the phosphorus blood level and helps it carry out all these essential functions.

Phosphorus has been used to treat many kinds of bone problems; it (along with calcium) helps in healing fractures by minimizing calcium loss from bones. It is used in the treatment of osteolmalacia, where there is decreased bone mineral content, and in osteoporosis, where total bone mass is decreased. Rickets has also been treated with phosphorus, as well as with calcium and vitamin D. Tooth and gum problems can be alleviated with dietary phosphorus, again in balance with calcium. Cancer research has revealed that cancer cells tend to lose phosphorus more readily than do normal cells, so phosphorus may be useful in the nutritional support of cancer patients; however, a high phosphorus-to-calcium intake is to be avoided.

Symptoms of phosphorus deficiency may include anorexia, appetite loss, arthritis, depression, irregular breathing, malaise, mental fatigue, nerve disorders, pain in bones, physical fatigue, pyorrhea, rickets, tooth decay, weakness, weight loss, irritability, anxiety, stiff joints, paresthesias, bone pain, and bone fragility. Decreased growth, poor bone and tooth development, and symptoms of rickets may occur in phosphorus-deficient children. In adults, as mentioned, a low calcium-to-phosphorus ratio is most likely to generate problems. Osteoporosis (bone resorption) is often brought on by high phosphorus and low calcium intake. Other adult problems include skin disease, tooth decay, and even arthritis. Low vitamin D intake can also lead to deficient body phosphorus.

Since phosphorus is part of all cells, it is readily found in food, especially animal tissues. Most protein foods are high in phosphorus. Meats, fish, chicken, turkey, milk, cheese, and eggs all contain substantial amounts. Most red meats and poultry have much more phosphorus than calcium-between 10 and 20 times as much-whereas fish generally has about 2 or 3 times as much phosphorus as calcium. The dairy foods have a more balanced calcium-phosphorus ratio. Seeds and nuts also contain good levels of phosphorus (although they have less calcium) as do the whole grains, brewer's yeast, and wheat germ and bran. Most fruits and vegetables contain some phosphorus and help to balance the ratio of phosphorus to calcium in a wholesome diet.