What Is Phosphorus?

Phosphorus is an essential mineral found in every cell of the human body. It is the second most abundant mineral next to calcium, accounting for roughly 1 percent of your total body weight. Phosphorus is one of 16 essential minerals. These are minerals that the body needs to function normally.

Although the main function of phosphorus is to build and maintain bones and teeth, it also plays a major role in the formation of DNA and RNA (the genetic building blocks of the body). Doing so helps ensure that cells and tissues are properly maintained, repaired, and replaced as they age.

Phosphorus also plays a key role in metabolism (the conversion of calories and oxygen to energy), muscle contraction, heart rhythm, and the transmission of nerve signals. Phosphorus is also considered a macromineral (alongside calcium, sodium, magnesium, potassium, chloride, and sulfur) in that you need more of it than trace minerals like iron and zinc.

A deficiency of phosphorus is usually accompanied by hypophosphatemia, or low blood phosphate levels, which can affect every organ system of the body and may lead to muscle weakness, bone pain, fractures, seizures, and respiratory failure. Unlike certain micronutrients, the body cannot produce phosphorus on its own. You need to obtain it from food and, if needed, a dietary supplement (phosphate is the drug form of phosphorus). The best food sources for phosphorus are meat, dairy, oily fish, and seeds.

What Is Phosphorus Used For?

A phosphate supplement is typically used to prevent a phosphorus deficiency, a condition considered rare in the United States outside of certain high-risk groups. According to a study from Harvard Medical School, phosphorus deficiency is most commonly seen in:

• people with chronic obstructive pulmonary disease (affecting 21.5 percent)
• chronic alcoholics (up to 30.4 percent)
• people in intensive care units (up to 33.9 percent)
• people involved in major trauma, such as a severe burn (75 percent)
• people with sepsis (up to 80 percent)

Low phosphorus can also affect people with certain diseases or medical conditions, including Cushing's disease, hypothyroidism, parathyroid disease, vitamin D deficiency, and malnutrition. Hypophosphatemia may also be caused by the overuse of diuretics (water pills) or phosphate-lowering drugs used during kidney dialysis.

Beyond the prevention or treatment of phosphorus deficiency, a phosphate supplement may offer specific health benefits, particularly in older adults and people prone to urinary tract infections (UTIs). It is also believed to enhance athletic performance and strength, although there is little clinical evidence to support this claim.

Osteoporosis

Around 85 percent of phosphorus in the human body is stored in bone. The rest is freely circulating in the bloodstream to facilitate other biological functions.

Phosphorus works with calcium to help build healthy bone and teeth. These minerals are converted in the body into calcium phosphate salts that stiffen and strengthen bones.

Phosphorus also regulates how much calcium is in the body and how much is excreted in urine. Doing so prevents excess calcium from being deposited in blood vessels, which can increase the risk of atherosclerosis (hardening of the arteries).

In the past, there was a concern that consuming too much phosphate could throw off this fine-tuned balance, drawing calcium from bone and increasing the risk of osteoporosis (bone mineral loss). A 2015 study published in the Nutrition Journal proved this wasn't the case.

Moreover, increased phosphate intake was not associated with toxicity. Any excess phosphate in the blood is excreted either in urine or stool.

Urinary Tract Infections

Phosphate supplements are sometimes used to make the urine more acidic. It has long been presumed that doing so can help treat certain urinary tract infections or prevent the formation of kidney stones. Recent studies, however, suggest that this may not be the case.

According to a 2015 study in the Journal of Biochemical Chemistry, urine with a high pH (meaning that it is less acidic) exerted stronger antimicrobial effects compared to urine with low pH/high acidity.

However, UTIs are more common in women with hypercalcemia (abnormally high calcium) as the increased urinary calcium promoted bacterial growth. Phosphate supplements may help reverse this risk by binding with free-circulating calcium and clearing it in the stool.

Similarly, kidney stones composed of calcium phosphate tend to develop when the urine pH is over 7.2 (meaning that it is alkaline). By lowering the pH (and increasing the acidity), phosphate may able to prevent kidney stones in high-risk individuals.

Though this is not true with all stones. Kidney stones composed of calcium oxalate develop when the urine pH is less than 6.0 (meaning that it is acidic). Increasing the acidity with phosphate may only promote, rather than inhibit, their growth.

Possible Side Effects

Phosphate supplements are considered safe if taken as prescribed. High doses can lead to headaches, nausea, dizziness, diarrhea, and vomiting.

Allergies to phosphate are rare, but it's still important to call your healthcare provider or seek emergency care if you experience rash, hives, shortness of breath, rapid heartbeat, or swelling of the face, throat, or tongue after taking a phosphate supplement. These could be signs of potentially life-threatening, whole-body reaction known as anaphylaxis.

Contraindications

People with chronic kidney disease may need to avoid phosphate supplements. Since the kidneys are less able to clear phosphate from the body, the mineral may accumulate and lead to hyperphosphatemia (excessively high phosphorus levels). Symptoms may include rash, itching, muscle cramps, spasms, bone or joint pain, or numbness and tingling around the mouth.

Excess phosphorus can also affect urine acidity and lead to the dislodgement of a previously undiagnosed kidney stone.

Outside of severe kidney dysfunction, hyperphosphatemia is extremely rare. it is more associated with the failure to clear phosphorus from the body rather than with the use of phosphate supplements.

Drug Interactions

Phosphate may interact with some pharmaceutical and over-the-counter medications. Certain drugs may cause decreases in phosphorus levels in the blood, including:

• angiotensin-converting enzyme (ACE) inhibitors like Lotensin (benazepril), Capoten (captopril), or Vasotec (enalapril)
• antacids containing aluminum, calcium, or magnesium
• anticonvulsants like phenobarbital or Tegretol (carbamazepine)
• cholesterol-lowering drugs like Questran (cholestyramine) or Colestid (colestipol)
• diuretics like Hydrodiuril (hydrochlorothiazide) or Lasix (furosemide)
• insulin

Other drugs may cause phosphorus levels to rise excessively, including:

• corticosteroids like prednisone or Medrol (methylprednisolone)
• potassium supplements
• potassium-sparing diuretics like Aldactone (spironolactone) and Dyrenium (triamterene)

If you are being treated with any of these medications, you should not take phosphate supplements without first speaking with your healthcare provider. In some cases, separating the drug doses by two to four hours will help overcome the interaction. In others, a dose adjustment or drug substitution may be needed.

Dosage and Preparation

Phosphate supplements are available in tablet or capsule form under various brand names. Phosphate is also included in many multivitamin/mineral supplements as well as co-formulated supplements designed specifically for bone health. Doses tend to range from 50 milligrams (mg) to 100 mg.

According to Food Nutrition Board of the Institute of Medicine, the recommended dietary intake (RDI) of phosphorus from all sources varies by age and pregnancy status, as follows:

• children zero to six months: 100 milligrams per day (mg/day)
• children seven to 12 months: 275 mg/day
• children one to three years: 460 mg/day
• children four to eight years: 500 mg/day
• adolescents and teens nine to 18 years: 1,250 mg/day
• adults over 18: 700 mg/day
• pregnant or lactating women 18 and under: 1,250 mg/day
• pregnant or lactating women over 18: 700 mg/day

Injectable phosphate is sometimes used to treat severe hypophosphatemia. Injections are generally indicated when the blood phosphorus level drops below .4 millimoles per liter (mmol/L). The normal range is .87 to 1.52 mmol/L.

Phosphate injections are only given in a healthcare setting under the direction of a qualified specialist.

What to Look For

Dietary supplements are largely unregulated in the United States and are not subject to the rigorous testing and research that pharmaceutical drugs are. Therefore, the quality can vary—sometimes significantly.

Phosphate supplements are vulnerable to extreme heat, humidity, and ultraviolet (UV) radiation. It is always best to store the supplements in their original light-resistant container in a cool, dry room. Never used expired supplements or supplements that are discolored or deteriorating, no matter the "use-by" date.

Other Questions

Do I need a phosphate supplement?

Most people get all the phosphorus they need from diet. Unless you have a medical condition that requires supplementation, like alcoholism or chronic obstructive pulmonary disease (COPD), you would be better served to eat a healthy, balanced diet rich in macro and trace nutrients.

Foods especially rich in phosphorus include:

• Pumpkin or squash seeds: 676 mg per 1/4-cup serving
• Cottage cheese: 358 mg per 1-cup serving
• Sunflower sees: 343 mg per 1/4-cup serving
• Canned sardines in oil: 363 mg per 2.5-ounce serving
• Hard cheese: 302 mg per 1.5-ounce serving
• Milk: 272 per 1-cup serving
• Lentils (cooked): 264 mg per 3/4-cup serving
• Canned salmon: 247 mg per 2.5-ounce serving
• Yogurt: 247 mg per 3/4-cup serving
• Pork: 221 mg per 2.5-ounce serving
• Tofu: 204 mg per 3/4-cup serving
• Beef: 180 mg per 2.5-ounce serving
• Chicken: 163 mg per 2.5-ounce serving
• Eggs: 157 mg per two eggs
• Canned tuna in water: 104 mg per 2.5-ounce serving