The majority of phosphorus in the body is used in the formation of teeth and bone, giving phosphorous a strong correlation with calcium: calcium phosphate is deposited and reabsorbed in bone formation.
The remaining phosphorus is involved in various aspects of metabolism and has an important role in every cell in the body.
- Through the process of phosphorylation, phosphorus combines with glucose and glycerol to promote their absorption into the intestine.
- As phospholipids, phosphorous transports fatty acids.
- Phosphorous is a component of ATP and plays a role in energy metabolism.
- Phosphorus is also involved in the control of acid-base states in blood.
Absorption and Excretion
Phosphate is absorbed in the jejunum of the small intestine. Absorption is regulated by calcium and the vitamin D hormone 1,23-dihydroxycholecalciferol. When phosphate serum level is low, the kidney is stimulated to produce the vitamin D hormone, which facilitates absorption of phosphorus in the intestine. Phosphorus is excreted through the kidneys based on the level of serum phosphorus.
Phosphorous absorption is good when it is obtained through meat sources. Phytic acid, found in cereal grains, reduces the bioavailability. Many antacids are phosphate-binding and reduce absorption.
Hypophosphatemia, or low serum phosphorus, is seen in intestinal diseases such as sprue and celiac disease, which hinder phosphorus absorption. Bone diseases such as rickets or osteomalacia also upset the calcium/phosphorus ratio. Chronic alcohol intake depletes phosphorus stores in the body. Hyperparathyroidism also results in low serum phosphorus levels due to an excess of parathyroid hormone stimulating renal tubular excretion.
Phosphorous deficiencies, called hypophosphatemia, affect the body in a number of ways, impairing proper growth and causing muscle weakness. In some cases, patients with low serum phosphorous have displayed cardiac arrythmias.
Hyperphosphatemia, or high serum phosphorus, is evident in people suffering from renal insufficiency or hypoparathyroidism. Tetany can also cause an upset of the calcium/phosphorus ratio.
The Daily Reference Intake (DRI) of phosphorus is 700 mg for adults, 1250 for adolescents, 460-500 for children, and 100-275 for infants.
Phosphorus is found in many of the same foods that are high in calcium. The best sources of phosphorus are milk and other dairy products. Meat and cereal grains are also good sources of phosphorus.
There is not a common use of supplemental phosphorus, although phosphate salts and milk are commonly used to treat hypothyroidism.