Phosphorus

foods containing phosphorus, including nuts and seeds, salmon, eggs, cheese

Phosphorus is a mineral that naturally occurs in many foods and is also available as a supplement. It plays multiple roles in the body. It is a key element of bones, teeth, and cell membranes. It helps to activate enzymes, and keeps blood pH within a normal range. Phosphorus regulates the normal function of nerves and muscles, including the heart, and is also a building block of our genes, as it makes up DNA, RNA, and ATP, the body’s major source of energy. [1]

The kidneys, bones, and intestines tightly regulate phosphorus levels in the body. If the diet lacks phosphorus or too little phosphorus is absorbed, several things happen to preserve its stores and try to maintain normal levels: the kidneys excrete less phosphorus in urine, the digestive tract becomes more efficient at absorbing phosphorus, and the bones release its stores of phosphorus into the blood. [1] The opposite actions occur in these organs if the body has adequate phosphorus stores.

Recommended Amounts

RDA:  The Recommended Dietary Allowance (RDA) for adult men and women 19+ years is 700 mg a day. Pregnancy and lactation require the same amount of phosphorus at 700 mg daily. [2]

UL:  The Tolerable Upper Intake Level (UL) is the maximum daily intake unlikely to cause harmful effects on health. The UL for phosphorus for adult men and women ages 19-70 years old is 4,000 mg daily, and for older adults 71+ years, 3,000 mg daily. The UL for pregnant and lactating women ages 14-50 years is 3,500 and 4,000 mg, respectively.

Phosphorus and Health

soda being poured into a glass

Another downside of soda

It’s well-known that soda and other sugary beverages are a risk factor for diabetes, heart disease, and obesity, but they can also wreak havoc on your teeth. The reason is not just sugar itself, which feeds the bacteria in our mouths that cause tooth decay, but the acids added to both sweetened sodas and diet sodas. Most sodas contain either or both phosphoric acid and citric acid. Frequently drinking any type of soda bathes the teeth in these acids, which wear down the enamel that is the protective outer layer of teeth. Teeth then become vulnerable to cavities and decay, as well as sensitivity to tooth pain when the nerves are exposed. Save soda drinks as an occasional treat, and consider seltzer water, a bubbly acid-free alternative.

Food Sources

A variety of foods naturally contain phosphorus, and the richest sources are dairy, red meat, poultry, seafood, legumes, and nuts. Phosphorus from these foods is called organic phosphorus. It is absorbed more efficiently from animal foods than plant foods. Plant foods like seeds, legumes, and whole grains contain a storage form of phosphorus called phytates or phytic acid that can reduce the mineral’s absorption. The body lacks an enzyme needed to break down phytic acid, so as it passes through the digestive tract it can bind not only to phosphorus but other minerals like iron and zinc. Cooking, sprouting, and soaking are some food preparation techniques that help to break down phytic acid so that phosphorus is more easily absorbed.

Inorganic phosphorus is a processed form added to foods to preserve color, moisture, and texture. It is found in fast foods, deli meats, canned and bottled beverages, and many other processed foods. Phosphate additives and preservatives are a significant contributor to phosphorus intakes, comprising up to 30% in the U.S. diet. [4] Inorganic phosphorus is very easily absorbed in the gut: about 90%, compared with 40-60% from natural animal and plant foods. [15] Phosphorus is also available in supplement form.

Signs of Deficiency and Toxicity

Deficiency

A phosphorus deficiency is called hypophosphatemia, defined by blood levels that fall below the normal range. However, blood levels of phosphate do not necessarily show the total amount of phosphorus in the body, as most of it is stored in bones and teeth. The most common causes of deficiency are kidney problems or a condition called hyperparathyroidism, in which too much parathyroid hormone is released that causes phosphorus to exit the body through urine. Also, the overuse of aluminum-containing antacids can bind to phosphorus and increase the risk of a deficiency.

A notable but less common occurrence of hypophosphatemia occurs with refeeding syndrome, seen in people with severe malnutrition. Patients who are malnourished from conditions like cancer, advanced liver disease, alcohol abuse, or anorexia nervosa may be started on supplemental nutrition feedings through a tube or vein. However because their starved state has reduced their ability to efficiently process food, reintroducing nutrition can cause problems. A sudden infusion of nutrients and calories causes an insulin surge, which results in rapid shifts in electrolytes and fluids in the blood. Blood levels of electrolyte nutrients like potassium, phosphorus, and magnesium may quickly drop. If untreated, refeeding syndrome can lead to respiratory failure, coma, cardiac arrest, and even death. The situation can be avoided by giving these electrolytes intravenously to the patient prior to the nutritional feedings.

Symptoms appearing with a phosphorus deficiency:

  • Poor appetite
  • Anemia
  • Muscle weakness
  • Bone pain
  • Bone disease (osteomalacia, rickets)
  • Confusion
  • Increased susceptibility to infections

Toxicity

A toxicity from phosphorus, called hyperphosphatemia, is rare because the body will regulate any excess levels in healthy individuals. It might occur with supplement use, but generally the use of phosphorus supplements is not common and the amount of phosphorus in them is typically not high. (2) People with hyperphosphatemia may show no symptoms; others may develop calcium deposits and hardening of soft tissues in the body, such as in the kidney, resulting from a disruption in the normal metabolism of calcium.

Did You Know?

  • Phosphorus is the second most abundant mineral in the body, second to calcium. About 85% of the body’s phosphorus is stored in bones and teeth.
  • Inorganic phosphorus as phosphorus additives are commonly found in foods like processed meats and baked goods as well as beverages like soda, iced teas, bottled coffee drinks, and flavored waters. Examples to look for in the ingredients list are phosphoric acid, dicalcium phosphate, sodium phosphate, and trisodium phosphate. If one is following a low phosphorus diet, it is important to be aware of these “hidden” well-absorbed dietary sources of phosphorus by reading food labels carefully.

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