Phosphorus

Chief functions

• Mineralization of bones and teeth
• Buffer system—aids in maintaining the acid-base balance of cellular fluids
• Growth and renewal of tissues—part of the DNA and RNA of every cell
• Phosphorus compounds—carry, store, and release energy in the metabolism of energy nutrients
• Extraction of energy from nutrients for many enzymes and vitamins
• Formation of part of the molecules of phospholipids, which are principal components of cell membranes
• Present in some proteins
• Absorption of glucose and glycerol
• Transport of fatty acids

Deficiency symptoms

• Not known to occur

Toxicity symptoms

• Calcification of soft tissues, particularly the kidneys

Nutrient-nutrient reactions and absorption

• Free phosphate is absorbed along the entire length of the small intestine
• Absorption is regulated by vitamin D hormone (calcitriol) and phosphate carrier proteins
• Phosphorus in food occurs as a phosphate compound joined with calcium; in order for absorption to occur, it must first split as a free mineral
• Any excess of other minerals depresses or decreases phosphorus absorption
• Phytates in whole grains prevent absorption of phosphorus
• Phosphorus works with B vitamins in energy metabolism

DRI=Dietary Reference Intakes
mg=milligram
ND=not determined

Tolerable upper limits are not defined at certain ages, because of a lack of data of adverse effects.

Dietary sources

• Best—milk, lean meats, liver, salmon, and navy beans
• Good—eggs and peanut butter

Groups at highest risk for deficiency

• Individuals on long-term use of anticonvulsant medications or antacids containing aluminum hydroxide
• Individuals placed on low-phosphorus formula diets

Other facts

• Second most abundant mineral in the body
• Phosphorus is present in every living cell
• The concentration of phosphorus in the blood is less than half that of calcium
  Approximately 85% of the body’s phosphorus is found combined with calcium in the crystals of the bones and teeth
• Kidneys are the main excretion route for phosphorus and regulate serum phosphorus levels

References
Sizer F, Whitney E. Nutrition Concepts and Controversies. 11th ed. Belmont, CA: Thomson & Wadsworth; 2008:219-259.

Somer E. The Essential Guide to Vitamins and Minerals. New York, NY: Harper Collins Publishers; 1992:1-65, 224-246, 287-293.

Schlenker E, Long S. Essentials of Nutrition and Diet Therapy. 9th ed. St Louis, MO: Mosby Elsevier; 2007:107-144.

National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: recommended intakes for individuals. Available at: http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&tax_subject=256&topic_id=1342&level3_id=5140. Accessed July 28, 2008.

Review Date 10/08
G-0804