Phosphorus

Second only to calcium in the body by quantity, most of it in bone, and part of every cell membrane and every molecule of ATP. Widely available in food, so the practical question is usually about too much rather than too little.

Builds bone alongside calcium, forms the backbone of DNA, and makes ATP — the molecule cells actually spend as energy.

• Dairy
• Meat and fish
• Nuts and seeds
• Legumes
• Cola drinks (as additives)

700 mg for most adults. The upper limit, past which harm becomes likely, is 4,000 mg.

Reference intakes are population figures. Pregnancy, illness, age and medication all move an individual’s needs, which is one of several reasons this page is information rather than advice.

Most at risk: Severe malnutrition, refeeding after starvation, and heavy alcohol use.

Rare from diet. Occurs in severe malnutrition, refeeding after starvation, alcohol dependence, and with long-term antacid use that binds phosphate.

Very rare. Causes bone pain, weakness and loss of appetite.

Every sign here has other, often likelier, explanations. A list of symptoms is a reason to look into something, never a diagnosis.

Serum phosphate is a routine test, most often ordered when kidney or bone problems are suspected.

Protein foods carry it: dairy, meat, fish, eggs, nuts and legumes. Phosphate additives in processed foods and cola drinks are absorbed more completely than the naturally occurring form.

Not usually supplemented outside specific medical contexts. In kidney disease the priority is normally reducing intake, not increasing it.

Excess matters mainly in kidney disease, where it accumulates and pulls calcium from bone. Phosphate additives in processed food are absorbed far more readily than natural phosphorus.