What does sodium phosphate do to your body? Functions, risks, and health effects

December 21, 2025 •

4 min read

Phosphate is a vital electrolyte, constituting about 1% of total body weight, and sodium phosphate plays several crucial roles in the body's functioning. This mineral compound is naturally found in many foods, but is also used as a food additive and a powerful medication, leading many to question what does sodium phosphate do to your body.

Quick Summary

Sodium phosphate is a compound containing essential electrolytes, playing a key role in bone mineralization, energy production, and cellular function. It also acts as a powerful laxative and is used as a food additive, with excessive intake posing risks to kidney and heart health.

Key Points

Essential Nutrient: Sodium phosphate is a vital source of phosphate, crucial for bone mineralization, energy production, and cellular function.
Powerful Laxative: Medically, it is used as a saline laxative to treat occasional constipation and for bowel cleansing before procedures like colonoscopies.
Food Additive: In processed foods, it functions as an emulsifier, pH regulator, and stabilizer to improve texture and shelf life.
Electrolyte Balance: Proper sodium phosphate levels are necessary for regulating electrolytes like calcium and potassium and maintaining the body's pH balance.
Risk of Overdose: Excessive intake, especially from laxatives, can cause hyperphosphatemia, severe electrolyte imbalances, and lead to kidney or heart damage.
Kidney Concerns: Individuals with kidney issues, older adults, and those taking certain medications are at higher risk for kidney injury from concentrated sodium phosphate.

Essential Functions of Sodium Phosphate

As a crucial source of phosphate, sodium phosphate is integral to numerous physiological processes that keep the body functioning properly. Phosphorus is the second most abundant mineral in the body and is necessary for building strong bones and teeth. Beyond structural support, its functions are deeply embedded in our cellular machinery.

Bone and Cellular Health

Approximately 85% of the body's phosphate is found in bones and teeth, where it helps form the mineral matrix. It is also a fundamental component of cell membranes, DNA, and RNA. Sodium phosphate is also vital for creating adenosine triphosphate (ATP), the body's primary energy currency, which powers almost all cellular activities.

Maintaining Electrolyte and pH Balance

As an electrolyte, sodium phosphate is critical for maintaining fluid balance and the electrical potential of cells. In the kidneys, it acts as a urinary buffer, helping to excrete excess acid and maintain the body's delicate acid-base equilibrium. Maintaining proper electrolyte balance is essential for normal nerve and muscle function.

Oxygen Transport

Phosphate also plays a lesser-known but important role in oxygen delivery. It helps regulate the synthesis of 2,3-bisphosphoglycerate, a compound in red blood cells that controls hemoglobin's ability to release oxygen to tissues.

Medicinal Uses and Effects

Beyond its natural role, sodium phosphate is used medicinally for its powerful effects on the gastrointestinal tract. As a saline laxative, it works by drawing water into the intestines, softening stool and stimulating bowel movements.

Bowel Preparation

For medical procedures like colonoscopies, doctors may prescribe oral or rectal sodium phosphate to completely cleanse the colon. The high concentration of the solution creates an osmotic effect, pulling fluid into the bowel and causing diarrhea. This clears the way for a clear view of the colon wall during examination.

Addressing Hypophosphatemia

For patients with abnormally low levels of phosphate in the blood (hypophosphatemia), intravenous or oral sodium phosphate can be administered to restore proper levels. This is especially important for those with conditions like malnutrition, chronic alcoholism, or after major surgery.

Sodium Phosphate as a Food Additive

Food-grade sodium phosphate, listed as E339 on food labels, is recognized as “generally recognized as safe” (GRAS) by the FDA. It is widely used in processed foods for several purposes:

Emulsifier and Stabilizer: Helps to combine water and oil in products like processed cheeses, sauces, and deli meats, improving texture and consistency.
Acidity Regulator: Controls pH levels in foods and beverages, which enhances shelf life and flavor.
Leavening Agent: Helps baked goods like cakes and cookies rise.
Moisture Retention: In processed meats, it helps bind water, improving the texture and moisture content.

Potential Health Risks and Side Effects

While naturally occurring phosphate is essential, excessive intake from supplements or processed foods can disrupt the body's delicate balance and pose serious risks, particularly to the kidneys.

Risk of Hyperphosphatemia

Overloading the body with phosphate can lead to a condition called hyperphosphatemia, where blood phosphate levels become dangerously high. This is a particular concern for individuals with impaired kidney function, who cannot excrete excess phosphate efficiently. Severe hyperphosphatemia can cause serious electrolyte imbalances, including dangerously low calcium levels (hypocalcemia), which can lead to muscle cramps, spasms, and cardiac arrest.

Kidney Injury

Studies have shown a link between high doses of oral sodium phosphate for bowel cleansing and acute kidney injury (AKI), especially in older patients or those with pre-existing kidney disease. The FDA has issued warnings regarding the risks of exceeding recommended dosages for over-the-counter sodium phosphate products. The risk is minimized by following strict medical supervision and staying properly hydrated.

Heart and Electrolyte Disturbances

Excess sodium phosphate intake can cause severe electrolyte disturbances, which may lead to irregular heartbeats (arrhythmias), seizures, and fainting. Patients with pre-existing heart conditions, especially congestive heart failure, should use sodium phosphate products with extreme caution.

Dietary vs. Medicinal Sodium Phosphate: A Comparison

To understand the full impact on your body, it's important to distinguish between dietary and medicinal sources.


Feature	Dietary Sodium Phosphate	Medicinal Sodium Phosphate
Source	Naturally occurring in foods (dairy, meat, nuts) and as a food additive (E339).	Prescribed tablets or enemas for medical purposes like bowel prep or treating hypophosphatemia.
Dose	Small, regulated amounts in food and beverages; total daily intake needs to be monitored, especially in those with kidney issues.	High, concentrated doses taken over a short period under medical supervision.
Effects	Contributes to normal bodily functions like bone and energy health. Excessive intake over time is concerning.	Powerful osmotic laxative for rapid bowel evacuation. Poses acute risks if misused or in high-risk patients.
Risk Profile	Low risk for healthy individuals when part of a balanced diet. Higher risk for those with impaired kidney function.	Elevated risk for electrolyte imbalance, kidney injury, and cardiac issues, especially in vulnerable populations or with overdose.

Conclusion

In summary, sodium phosphate is a dual-edged sword. On one hand, it supplies the body with the essential mineral phosphate, which is indispensable for skeletal integrity, cellular energy, and electrolyte balance. On the other hand, its concentrated medicinal form acts as a potent laxative, and misuse or excessive intake can lead to severe health consequences. While food-grade sodium phosphate is generally considered safe in small amounts, vigilance is key for individuals with chronic health conditions like kidney disease. Always follow a healthcare provider's instructions carefully when using medicinal products to ensure safety and avoid the serious risks associated with overdose or improper use.

For more information regarding the risks of over-the-counter sodium phosphate products, please refer to this FDA Drug Safety Communication.

Frequently Asked Questions

The primary role of sodium phosphate is to serve as a source of phosphate, an essential electrolyte. It is crucial for building and maintaining strong bones and teeth, producing cellular energy (ATP), and regulating the body's electrolyte and pH balance.

Excessive intake of sodium phosphate, particularly from high-dose laxative preparations, can be harmful to the kidneys. Individuals with pre-existing kidney disease, the elderly, or those who are dehydrated are at a higher risk for developing acute kidney injury.

As a saline laxative, sodium phosphate works by drawing large amounts of water into the intestines. This softens the stool and increases pressure, triggering bowel muscle contractions to produce a rapid bowel movement.

Yes, food-grade sodium phosphate (E339) is generally recognized as safe (GRAS) by the FDA. It is used in processed foods as a stabilizer and emulsifier, and the amounts added are typically low and safe for consumption by healthy individuals.

People with kidney disease, heart failure, intestinal blockages or tears, and those taking certain medications (like diuretics or some blood pressure meds) should avoid or use sodium phosphate with extreme caution.

Symptoms of a sodium phosphate overdose can include serious electrolyte imbalances, seizures, irregular heartbeat, severe dehydration, abdominal pain, nausea, vomiting, and decreased urination.

Some studies have explored sodium phosphate supplementation for enhancing athletic endurance by increasing aerobic capacity. However, evidence is mixed, and high doses can cause digestive issues or electrolyte imbalances. Any supplementation should be monitored by a healthcare provider.