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Phosphorus

What is phosphorus?

Phosphorus is the second most abundant mineral in the body behind calcium, making up approximately one percent of a person's body weight. It is present in every cell in the body; however, most phosphorus (85%) is concentrated in the bones and teeth.

Why do we need it?

Phosphorus takes part in almost every metabolic reaction in the body. It is necessary for the conversion of dietary carbohydrates, fats and proteins to energy, and forms part of the adenosine triphosphate (ATP) molecule which acts as a reservoir of energy in cells.

Phosphorus combines with calcium to form hydroxyapatite, a major component of the structural part of bones and teeth. It is also a component of some of the major building blocks in the body, including RNA, DNA, and lipids found in the blood and cell membranes..

How much phosphorus should I take?

According to the National Academy of Sciences, the recommended daily allowance (RDA) for phosphorus is as follows:

• Adult men: 700 milligrams/day
• Adult women: 700 milligrams/day
• Children aged 7-10: between 500-1250 milligrams/day
• Infants: between 275-500 milligrams/day
• Pregnant/lactating women: 700 milligrams/day

What are some good sources of phosphorus?

Phosphorus is most prevalent in protein-rich foods such as meat, poultry, cheese and milk; smaller amounts are found in breads and cereals made from refined flour. Most soft drinks contain large amounts of phosphorus, which may lead to excessive intake.

What can happen if I don't get enough phosphorus?

Because phosphorus is so abundant in the average diet, deficiencies are extremely rare. However, alcoholics and patients with kidney or liver disorders may have difficulty absorbing phosphorus. In addition, some antacids that contain large amounts of aluminum may block phosphorus absorption.

Deficiency symptoms include weakness, loss of appetite, bone pain, joint stiffness, irritability, numbness, speech disorders, tremors and mental confusion. Red blood cells may die earlier than normal, leading to anemia. White blood cells may also be affected, which leading to reduced resistance to infection.

What can happen if I take too much?

High levels of phosphorus lead to calcium deficiency. This loss of calcium may in turn increase the risk of disorders such as kidney stones, osteoporosis and atherosclerosis. Excess phosphorus intake can also prevent absorption of iron, magnesium and zinc and decrease vitamin D levels, which may increase the risk of bone disorders and cancer. A 1997 study involving 376 heart disease patients found a relationship between high phosphorus levels and the severity of coronary heart disease.

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References

• Recommended Dietary Allowances, 10th ed. Washington, D.C.: National Academy Press, 1989.
• Chan JM, et al. Dairy products, calcium, phosphorous, vitamin D, and risk of prostate cancer. Cancer Causes Control Dec 1998;9(6):559-66.
• Gomez-Ayala AE, et al. Effect of source of iron on duodenal absorption of iron, calcium, phosphorous, magnesium, copper and zinc in rats with ferropoenic anemia. Int J Vitam Nutr Res 1997;67(2):106-14.
• Grenby TH, Saldanha MG. The use of high-phosphorus supplements to inhibit dental enamel demineralization by ice lollies. Int J Food Sci Nutr 1995;46:275-9.
• Calvo MS, Park YK. Changing phosphorus content of the U.S. diet: potential for adverse effects on bone. J Nutr Apr 1996;126:4, Suppl, 1168S-80S.
• Narang R, Ridout D, Nonis C, Kooner JS. Serum calcium, phosphorus and albumin levels in relation to the angiographic severity of coronary artery disease. Int J Cardiol Jun 1997;60:1, p. 73-9.