Phosphorus, a key element of bones, teeth, and cell membranes

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.

How it work in our body
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. The opposite actions occur in these organs if the body has adequate phosphorus stores.

Although phosphorus status is not typically assessed, phosphate can be measured in both serum and plasma. In adults, normal phosphate concentration in serum or plasma is 2.5 to 4.5 mg/dL (0.81 to 1.45 mmol/L). Hypophosphatemia is defined as serum phosphate concentrations lower than the low end of the normal range, whereas a concentration higher than the high end of the range indicates hyperphosphatemia. However, plasma and serum phosphate levels do not necessarily reflect whole-body phosphorus content.

Interaction's Phosphorus and Calcium
Phosphorus and calcium are interrelated because hormones, such as vitamin D and parathyroid hormone (PTH), regulate the metabolism of both minerals. In addition, phosphorus and calcium make up hydroxyapatite, the main structural component in bones and tooth enamel. The combination of high phosphorus intakes with low calcium intakes increases serum PTH levels, but evidence is mixed on whether the increased hormone levels decrease bone mineral density.

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.

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 intakes and status
Most Americans consume more than the recommended amounts of phosphorus. Data from the 2015–2016 National Health and Nutrition Examination Survey (NHANES) show that among children and teens age 2–19 years, the average daily phosphorus intake from foods is 1,237 mg. In adults age 20 and older, the average daily phosphorus intake from foods is 1,189 mg for women and 1,596 mg for men.

According to an analysis of 2013–2014 NHANES data, the average daily phosphorus intake from both foods and supplements is 1,301 mg for women and 1,744 mg for men. Some experts question whether the dietary data collection instruments used by NHANES and other large population-based studies capture true dietary phosphorus intakes because these surveys do not account for the additional contributions of phosphate additives in foods.

Groups at Risk of Phosphorus Inadequacy
Phosphorus deficiency (hypophosphatemia) is rare in the United States and is almost never the result of low dietary intakes. The effects of hypophosphatemia can include anorexia, anemia, proximal muscle weakness, skeletal effects (bone pain, rickets, and osteomalacia), increased infection risk, paresthesias, ataxia, and confusion. In most cases, hypophosphatemia is caused by medical conditions, such as hyperparathyroidism, kidney tubule defects, and diabetic ketoacidosis.

1.Preterm newbornsPhosphorus deficiency in preterm infants is one of the main causes, along with calcium deficiency, of osteopenia of prematurity (impaired bone mineralization). Because two-thirds of fetal bone mineral content is acquired during the third trimester of pregnancy, preterm infants are born with low stores of calcium and phosphorus in their bones. The benefits of providing extra phosphorus and calcium for bone health in preterm babies is not clear. However, milk fortified with higher amounts of these minerals and other nutritional components is typically recommended to support overall growth and development.

2. People with genetic phosphate regulation disordersRare genetic disorders of phosphorus metabolism include X-linked hypophosphatemic rickets. In addition to rickets, patients with this disease develop osteomalacia, pseudofractures (formation of new bone and thickened connective tissue over injured bone), enthesopathy (mineralization of ligaments and tendons), and dental damage. Other rare genetic disorders of phosphorus regulation associated with rickets include autosomal-dominant and autosomal-recessive hypophosphatemic rickets and hereditary hypophosphatemic rickets with hypercalciuria. Treatment typically consists of vitamin D and phosphorus supplementation from diagnosis until growth is complete.

3. Patients with severe malnutritionPeople with severe protein or calorie malnutrition can develop refeeding syndrome, also known as refeeding hypophosphatemia, within 2 to 5 days of starting enteral or parenteral nutrition because of the shift in metabolism from a catabolic to an anabolic state. Causes of malnutrition that can lead to refeeding syndrome include chronic diseases (e.g., cancer, chronic obstructive pulmonary disease, or cirrhosis), very low birthweight, cachexia, low body weight, anorexia nervosa, excessive alcohol intake, and chewing or swallowing problems. The effects of refeeding syndrome can include impaired neuromuscular function, hypoventilation, respiratory failure, impaired blood clotting, confusion, coma, cardiac arrest, congestive heart failure, and death. Prophylactic administration of phosphorus and thiamin in patients at risk of refeeding syndrome can prevent this condition.

Phosphorus sources
1. Food A variety of foods naturally contain phosphorus, and the richest sources are dairy (milk, yogurt, cheese), red meat (beef, salmon), poultry, pork, seafood, legumes, some vegetables (asparagus, tomatoes, cauliflower), nuts and whole wheat breads and cereals. 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 (especially deli meats, bacon, sausage, sodas, sports drinks, and other bottled beverages). Phosphate additives and preservatives are a significant contributor to phosphorus intakes, comprising up to 30% in the U.S. diet. Inorganic phosphorus is very easily absorbed in the gut: about 90%, compared with 40-60% from natural animal and plant foods. Phosphorus is also available in supplement form.

2. Another downside of sodaIt’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.

3. Dietary supplementsPhosphorus is available in dietary supplements containing only phosphorus, supplements containing phosphorus in combination with other ingredients, and a few multivitamin/mineral products. Phosphorus in supplements is usually in the form of phosphate salts (e.g., dipotassium phosphate or disodium phosphate) or phospholipids (e.g., phosphatidylcholine or phosphatidylserine). Products typically provide 10% or less of the DV for phosphorus, but a small proportion deliver more than 100%.

The bioavailability of phosphate salts is approximately 70%. The bioavailability of other forms of phosphorus in supplements has not been determined in humans.

Low phosphorus diet
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.

Phosphorus and Health
1. Chronic kidney diseaseKidneys help to regulate normal levels of phosphorus in the body. If the body has adequate stores of the mineral, the kidneys will push out extra phosphorus in the urine. With chronic kidney disease (CKD), the kidneys cannot perform this action and the amount of phosphorus can rise to harmful levels in the blood. Studies show that adults with CKD have higher phosphate levels than those with normal kidney function. This may quicken the progression of CKD, and increase the risk of cardiovascular disease, bone disorders, and death. It appears that patients with higher phosphate levels and more advanced levels of CKD (such as those on dialysis) have a greater risk of disease progression and death than those with milder forms of CKD.

Even so, it is unclear if lowering phosphate levels in those with CKD improves health outcomes later on. Dietary recommendations for phosphorus depend on how much the disease has progressed, and a person’s blood level of phosphorus. Some recommendations suggest limiting animal protein while increasing plant proteins, and reading food labels to limit foods with phosphate additives. Plant-based proteins like legumes, nuts, and seeds contain phytates, which interfere with the absorption of phosphorus in the gut. Medications like phosphate binders are also sometimes prescribed to be taken with food to reduce the amount of phosphorus absorbed in the gut.

2. Cardiovascular diseaseSome studies have found that excess phosphorus can promote the calcification, or hardening, of heart arteries and increase inflammation. Higher phosphate levels may be associated with an increased risk of cardiovascular disease (CVD). A meta-analysis of six cohort studies of more than 120,000 healthy adults followed for up to 29 years showed a 36% increased risk of deaths from CVD and all causes in those with the highest levels of serum phosphorus, compared with the lowest levels. Deaths from all causes were seen mainly in men, not women.

The foods highest in phosphorus are animal proteins, which also tend to be high in other components related to CVD, like saturated fat. So it is not clear if phosphorus alone is associated with an increased risk of CVD, or if high levels are an indicator of another risk factor. The research is also unclear if restricting dietary phosphorus can prevent CVD in otherwise healthy adults.

3. Bone healthElevated phosphorus levels may disrupt the normal hormonal balance of phosphorus, calcium, and vitamin D that regulates bone health. Animal studies have shown that high dietary phosphorus intakes are detrimental to bone health. Yet the evidence is less clear in humans, partly because it is difficult to estimate accurate phosphorus intakes. Most studies measure phosphorus in the blood, which may not reflect true dietary intakes of phosphorus, since the majority of the mineral is stored in bones and the body maintains blood levels within a specific range. However, research has shown that a higher intake of phosphate additives, from various foods like cola beverages and salad dressings that are very well-absorbed in the gut, are associated with negative effects on bone metabolism. These include fractures and a lower bone mineral density. More research is needed in this area.

Signs of Deficiency and Toxicity
1. DeficiencyA 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.

2. ToxicityA 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. 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.

Health Risks from Excessive Phosphorus
High phosphorus intakes rarely produce adverse effects in healthy people. Although some studies have found associations between high phosphorus intakes (1,000 mg/day or higher) and cardiovascular, kidney, and bone adverse effects as well as an increased risk of death, others have found no link between high intakes and increased disease risk. The ULs for phosphorus from food and supplements for healthy individuals are therefore based on intakes associated with normal serum phosphate concentrations. The ULs do not apply to individuals who are receiving supplemental phosphorus under medical supervision.

The below table shows tolerable upper intake levels (ULs) for Phosphorus
Age Male Female Pregnancy Lactation
√ Birth to 6 months*: None established*
√ 7–12 months*: None established*
√ 1–3 years: 3,000 mg
√ 4–8 years: 3,000 mg
√ 9–13 years: 4,000 mg
√ 14–50 years: 4,000 mg; 3,500 mg for pregnancy; 4,000 mg for lactation.
√ 51–70 years: 4,000 mg
√ 71+ years: 3,000 mg

Breast milk, formula, and food should be the only sources of phosphorus for infants.
According to one analysis of data on healthy U.S. adults using NHANES III data collected in 1988–1994, high phosphorus intakes (1,000 mg/day or more) were associated with increased rates of all-cause and cardiovascular mortality in adults through 2006. These intakes are twice the RDA for adults—less than daily intakes in many men (especially those who are white or Hispanic) and well below the UL. The implications of this analysis for the potential adverse effects of high phosphorus intakes are unclear. High phosphorus intakes might be signs of diets that are unhealthy in other ways, for example.

Very high phosphorus intakes over short periods (e.g., two 6,600 mg doses of sodium phosphate taken in 1 day) can cause hyperphosphatemia. The main effects of hyperphosphatemia include changes in the hormones that regulate calcium metabolism and calcification of nonskeletal tissues, especially in the kidney.

Phosphorus and Healthful Diets
The federal government’s 2020–2025 Dietary Guidelines for Americans notes that “Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods. … In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients (e.g., during specific life stages such as pregnancy).”

For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americansexternal link disclaimer and the USDA’s MyPlate.external link disclaimer

The Dietary Guidelines for Americans describes a healthy dietary pattern as one that.

- Includes a variety of vegetables; fruits; grains (at least half whole grains); fat-free and low-fat milk, yogurt, and cheese; and oils. Some dairy products are rich in phosphorus, and some vegetables, fruits, and grains contain phosphorus.

- Includes a variety of protein foods such as lean meats; poultry; eggs; seafood; beans, peas, and lentils; nuts and seeds; and soy products. Some meats, seafoods, fish, and nuts and seeds are rich in phosphorus or are good sources of the mineral, and other types of meats, fish, and beans contain phosphorus.

- Limits foods and beverages higher in added sugars, saturated fat, and sodium. Limits alcoholic beverages.

- Stays within your daily calorie needs.

Compiled and penned by Crocus Media