chapter  9
16 Pages

Inorganic Phosphorus: Do Higher Dietary Levels Affect Phosphorus Homeostasis and Bone?

The adult body contains approximately 600 g of phosphorus as both inorganic and organic phosphorus (Endres and Rude, 2006). Approximately 510 g or 85% of total body phosphorus is contained in the adult skeleton as organic and inorganic phosphates, and soft tissues contain 15% as both inorganic and organic phosphate, whereas the extracellular —uid contains 0.1% largely as inorganic phosphorus. Cellular phosphates function in many energy-intensive physiologic functions such as muscle contraction, nerve conduction, electrolyte transport, and energy production, in addition to

Introduction .................................................................................................................................... 141 Inorganic Phosphorus and Bone .................................................................................................... 142

Inorganic Phosphorus Balance .............................................................................................. 142 Bone ......................................................................................................................................143

Dietary Phosphorus ........................................................................................................................ 143 Differences in Organic and Inorganic Phosphorus in Food .................................................. 143 Phosphorus Additives in Food .............................................................................................. 143 Dietary Guidelines for Phosphorus Intake ............................................................................ 147 Total Dietary Phosphorus Intake ........................................................................................... 147

Current Understanding of the Regulation of Phosphorus Homeostasis ......................................... 149 Regulation by Novel Intestinal Phosphate Sensor ................................................................ 149 Classical Endocrine Regulation ............................................................................................ 149 Phosphatonin Regulation ...................................................................................................... 150

Physiologic Effects of High Inorganic Phosphorus Diet ............................................................... 151 Effects on Bone Health ......................................................................................................... 151 Effects on Cardiovascular Health ......................................................................................... 153

Summary ........................................................................................................................................ 153 References ...................................................................................................................................... 154

providing the main structural support of the body as a component of bone mineral. Intracellular phosphates are critical to the regulation of intermediary metabolism of proteins, fats and carbohydrates, gene transcription, and cell growth (Endres and Rude, 2006). These tissue functions are very sensitive to —uxes of inorganic phosphate into soft tissues when blood levels increase due to dietary loading or failing kidney function. To maintain homeostasis of phosphorus, exquisitely sensitive physiologic mechanisms have evolved to tightly regulate the level of inorganic phosphorus in the extracellular —uid (Calvo and Carpenter, 2003).