Phosphorus

What Is Phosphorus?

Phosphorus is the second most plentiful mineral in the body after calcium. About 85% of it is in bones and teeth, bound to calcium as the mineral that makes them hard. The other 15% is spread through every cell and the fluid around them, almost always as phosphate.

What Phosphorus Does in the Body

Phosphate forms the backbone of DNA and RNA. It is the P in ATP, adenosine triphosphate, the molecule that carries energy to every process in the cell. It makes up the phospholipids in cell membranes, and it helps keep the blood at a steady pH by soaking up excess acid.

Three Kinds of Phosphorus in Food

In meat, fish, eggs and dairy, phosphorus is absorbed well. In beans, nuts, seeds and whole grains, much of it is stored as phytate, which people cannot fully digest because the gut lacks the enzyme phytase, so less of it is absorbed. Yeast in bread dough breaks down some phytate, which makes the phosphorus in leavened bread easier to absorb.

The third kind is added. Phosphate salts are used in processed meats, processed cheese, baked goods and soft drinks to hold moisture, raise dough or adjust acidity. They are absorbed more readily than the phosphorus that occurs naturally in food, and they add to the total without showing up as a separate figure on most labels.

How Much Phosphorus One Day of Food Gives

One ordinary day from foods in the Caltide library, in usual portions, with nothing processed and no supplements.

Unlike most minerals on these pages, phosphorus is hard to fall short of. Any day with protein foods covers it, which is why the concern for most people is never too little.

Phosphorus and Kidney Disease

Healthy kidneys pass the phosphorus the body does not need into urine. In chronic kidney disease they cannot, and blood phosphorus rises. Over time high phosphate, together with calcium, can deposit in blood vessels and soft tissue, and it is linked to heart disease. People with kidney disease are often asked to limit phosphorus, especially from additives.

Low Phosphorus (Hypophosphatemia)

Low phosphorus, called hypophosphatemia, is rare and almost never caused by an ordinary diet. It is seen in premature babies, in alcohol use disorder, in diabetic ketoacidosis, in people restarting food after starvation (refeeding syndrome), and with long-term use of aluminum antacids, which bind phosphate in the gut.

Common Phosphorus Mistakes

Taking phosphorus for bones. Bones need it, but nearly everyone already eats plenty. Calcium and vitamin D are the nutrients more often short.

Blaming cola alone. A can of cola has less phosphorus than a serving of most protein foods. The bigger hidden source is additives in processed meat, cheese and baked goods.

Looking for phosphorus on the nutrition panel. Additives are easier to spot in the ingredient list: look for words containing phos, such as sodium phosphate or phosphoric acid.