Phosphorus 

Phosphorus, similar to calcium, is found mostly in bones and is in the form of phosphate in food and the body (PO-4). Phosphate can be found in phosphoric acid, phospholipids, phosphoproteins, and phosphorylated sugars.¹ Plant storage of phosphorus is known as phytates.

Absorption:  Phosphates that are attached to organic molecules are liberated to their inorganic form. Phytate is converted to phosphate less than other organic forms due to the lack of phytase within the body.¹ Absorption occurs within the small intestine through active transport (stimulated by vitamin D) or diffusion and ranges between 50-90% depending on intake.¹

Absorption is affected by other minerals; for example, increased calcium and magnesium in a meal decreases the absorption of phosphorus.¹ Meals low in magnesium promote phosphorus absorption while aluminum can decrease absorption.¹ 

Circulation and Excretion: Most phosphorus within the blood is found as phospholipids (70%) in proteins, lipoproteins, cells, and platelets.¹ The remaining is dissolved inorganic phosphates or bound to proteins or minerals (calcium and magnesium). Blood levels of phosphorus are regulated similarly to calcium by the use of parathyroid hormone and vitamin D. Specific proteins also play a role in the regulation of serum phosphorus levels, known as Fibroblast Growth Factor 23 (FGF 23) and Klotho.¹ Approximately, two-thirds of dietary phosphorus is excreted within the urine.¹

Functions:  

Energy Metabolism- Phosphorus is found in energy molecules ATP and GTP that are responsible for energy-requiring reactions/metabolism. 

Cell Signaling - ATP is a precursor for a molecule known as cAMP (cyclic adenosine monophosphate) which contains phosphorus. cAMP is a second messenger within the body involved in various cell signaling and regulation activities.¹

Functionality of Molecules- DNA and RNA are connected by bonds containing phosphorus, and vitamin B6 and vitamin B1 also require phosphorus. 

Structure - Phosphorus has a structural role in forming bones and teeth as a component of hydroxyapatite.¹

Other Roles - Phosphorus is also found to be responsible for the regulation of pH in extracellular fluid, contractions within muscles, absorption using active transport pumps, and producing glycogen.¹

Dietary Reference Intake (DRI) - The recommended dietary allowance (RDA) for adult men and women (19 years and older ) is 700 milligrams (mg).²

Deficiency/Toxicity- Phosphorus deficiency is rare due to the abundance of foods containing phosphorus. Toxicity is also uncommon due to the body’s ability to excrete dietary phosphorus. 

Dietary Sources of Phosphorus 

Phosphorus is found in many foods, such as meat/poultry, seafood, dairy, legumes, and grains. Dark sodas, teas, and coffee also contain phosphorus in the form of phosphoric acid. In grains, phytates are the predominant form of phosphorus.¹

Examples of foods containing phosphorus include:

Dairy - yogurt, milk, cheese 

Vegetables - potatoes, peas, corn 

Meat/Seafood/Animal Products- salmon, chicken, eggs

Legumes - lentils, kidney beans, peas

Grains - oatmeal, bread, tortillas 

Source(s):

1. Denise M Medeiros and Robert E.C. Wildman, Advanced Human Nutrition, 4th ed. (Burlington, MA: Jones & Bartlett, 2019).

2. https://ods.od.nih.gov/factsheets/Phosphorus-HealthProfessional/