Define Absorption, transport and Excretion of phosphorus?
As you have seen that food contains both organic and inorganic phosphorus, but most of it is absorbed in its inorganic form. Therefore, organically bound phosphorous is hydrolyzed in the lumen by intestinal phosphatases. However, organic phosphate of phytic acid may not be available. Phosphorus absorption occurs throughout the small intestine, although duodenum and jejunum are important sites. Phosphorus absorption is efficient-60-70%.
Ingestion of antacids containing magnesium or aluminium hydroxide can interfere with phosphorus absorption. It is important to note that unlike calcium, absorption efficiency of phosphorus does not increase on low intake nor any adaptive mechanism is available for the same. Most phosphorus is absorbed by passive concentration dependent process. However, a portion of phosphorus is absorbed by active transport, facilitated by calcitriol. Unabsorbed phosphorus is excreted in faeces.