How much phosphorus per day and the upper limit

Short answer: The NIH Office of Dietary Supplements sets the Recommended Dietary Allowance for phosphorus at 700 mg per day for adults, with a Tolerable Upper Intake Level of 4,000 mg per day for adults aged 19 to 70. Most Americans already meet or exceed the daily target through food alone, so supplementation is rarely necessary for healthy people.

What is phosphorus and why does the body need it?

Phosphorus is an essential mineral found in nearly every cell of the body. According to the NIH Office of Dietary Supplements, it serves several well-established physiological roles.

• Bone and tooth structure: Phosphorus combines with calcium to form hydroxyapatite, the mineral compound that gives bones and teeth their hardness and strength.
• Genetic material: It is a structural building block of DNA and RNA, the molecules that carry and express genetic information.
• Cell membranes: Phosphorus forms phospholipids, the key components that make up the structure of every cell membrane in the body.
• Energy metabolism: Phosphorus is part of adenosine triphosphate (ATP), the molecule cells use to store and transfer energy.

These roles are supported by strong evidence, meaning they reflect consistent findings across a large body of research, as graded by the NIH.

How much phosphorus per day do adults need?

The NIH Office of Dietary Supplements publishes the following Dietary Reference Intake values for phosphorus in adults.

• Recommended Dietary Allowance (RDA): 700 mg per day for adults 19 years and older, including during pregnancy and lactation.
• Tolerable Upper Intake Level (UL) for adults 19 to 70 years: 4,000 mg per day from all sources combined, including food, beverages, and supplements.
• Tolerable Upper Intake Level for adults 71 years and older: 3,000 mg per day.

These are population reference values intended for general guidance. They are not personal dosing recommendations. Please consult a clinician or pharmacist to determine what is appropriate for your individual health situation.

Are most people getting enough phosphorus?

Dietary deficiency of phosphorus is rare in the United States. The NIH Office of Dietary Supplements notes that most Americans consume more than the recommended amount through everyday foods. Phosphorus is found naturally in protein-rich foods such as meat, poultry, fish, eggs, dairy products, nuts, and legumes. It is also added to many processed foods as a preservative or flavor enhancer.

Because typical dietary intake is already sufficient for most healthy adults, taking a phosphorus supplement without a specific clinical reason is generally not necessary.

Is it possible to get too much phosphorus?

For healthy people, the NIH Office of Dietary Supplements notes that high phosphorus intakes seldom cause problems. The kidneys are efficient at excreting excess phosphorus in people with normal kidney function.

However, total intake from food, beverages, and supplements should stay below the age-specific Tolerable Upper Intake Level unless a health care provider advises otherwise. Exceeding the UL over time may raise serum phosphate levels, which carries different implications depending on a person's health status (see the section on kidney disease below).

Note that supplements are not intended to diagnose, treat, cure or prevent any disease and these statements have not been evaluated by the FDA.

Phosphorus and chronic kidney disease: what the evidence shows

The relationship between phosphorus and kidney health has received significant research attention. Here is how the NIH grades the current evidence.

• Higher serum phosphate and kidney disease outcomes (Moderate evidence): Higher serum phosphate levels are associated with increased mortality and disease progression in people with severe or end-stage chronic kidney disease.
• Limiting dietary phosphorus in chronic kidney disease (Limited evidence): There is limited evidence that restricting dietary phosphorus improves patient-centered outcomes in people with chronic kidney disease. More research is needed before firm conclusions can be drawn.
• Higher serum phosphate and cardiovascular risk in healthy people (Insufficient evidence): Some research suggests higher serum phosphate levels may increase cardiovascular disease risk in the general healthy population, but the NIH grades this evidence as insufficient at this time.

If you have kidney disease, heart disease, or any chronic condition, talk to your doctor before changing your phosphorus intake or starting any supplement.

Drug and nutrient interactions to know

Phosphorus absorption and blood levels can be affected by certain medications and other nutrients. The NIH Office of Dietary Supplements highlights the following interactions.

• Antacids containing aluminum hydroxide or calcium carbonate (for example Maalox, Rulox, Rolaids, and Tums) can reduce phosphorus absorption. Using these antacids for three months or longer can lead to low phosphorus levels.
• Sodium phosphate-containing laxatives (for example Fleet Prep Kit #1) can raise phosphorus levels. Taking more than the recommended dose can be dangerous, especially in people with dehydration, kidney disease, or heart disease.
• High calcium intake from foods and supplements can bind phosphorus in the gut and prevent its absorption. According to the NIH, a very high calcium intake of 2,500 mg per day binds an estimated 0.61 to 1.05 g of phosphorus.

Always talk to a doctor or pharmacist before combining phosphorus supplements with any medication or other dietary supplement.

Practical takeaways

• The adult RDA for phosphorus is 700 mg per day, according to the NIH Office of Dietary Supplements.
• The upper limit is 4,000 mg per day for adults aged 19 to 70, and 3,000 mg per day for adults 71 and older.
• Most healthy Americans already meet their phosphorus needs through food.
• People with kidney disease, heart disease, or those taking antacids or laxatives regularly should speak with a clinician before adjusting phosphorus intake.
• These figures are population reference values. For personal guidance, consult a qualified health care provider.

Sources

All data in this guide is drawn from the NIH Office of Dietary Supplements Phosphorus fact sheets (Health Professional and Consumer versions) and the National Academies Dietary Reference Intakes report, available at ods.od.nih.gov and ncbi.nlm.nih.gov/books/NBK109825/.