Dietary Phosphate

Dietary Phosphate

by Tumwebaze Joel
Graduate researcher
Makerere University

Phosphate is a salt and an ester of phosphoric acid with an empirical formula PO₃⁻⁴ and a molar mass of 94.97 g/mol.d. Phosphorus is widely distributed in the body tissues and fluids. About 80% of total body phosphorus (750 g) is in the bone as insoluble calcium phosphate, and the remaining 15% is in the skeletal muscles.

Absorption: 85% of ingested phosphorus is absorbed. The organic phosphates are digested in the intestines to form inorganic phosphates of sodium, calcium and potassium, and are absorbed from the upper small intestine. Excess calcium and aluminum form insoluble phosphates and decrease phosphate absorption.

Benefits: Necessary for bone formation; intermediate metabolism of Carbohydrates and fats; proper function of enzyme systems; Principal anion in the cells; Phosphate is a part of the molecular structure of phospholipids, an essential element in the phospholipid cell membranes, nucleic acids and phosphoproteins required in mitochondrial function; Is also the source of high energy bonds of ATP. The energy stored in ATP fuels a wide variety of physiological processes. Phosphorus is an essential compound of RNA and DNA, the key components in the structure of cell membranes. The phosphate group is of primary importance in glycolysis. Phosphate is instrumental in maintaining the acid/base balance in the body by acting as a buffer. It also activates many of the vitamin B-Complex vitamins, allowing them to function as coenzymes in various metabolic processes.

Recommended dosage of Phosphate; The daily requirement is about 1 g (32.29 mmol), which is easily supplied in an average diet. Dietary deficiency; therefore, never occurs under normal circumstances.

Phosphate Deficiency symptoms; Low serum phosphorus occurs during starvation, malabsorption; hyperparathyroidism, vitamin D deficiency, diabetic ketoacidosis, acute alcoholism, severe bums, nasogastric suction, and respiratory alkalosis; and with phosphate-binding antacids, intravenous glucose administration, and high estrogen doses in metastatic prostate cancer.

Clinical Manifestations; Clinically, low phosphate results in loss of appetite, nausea, weakness and malaise, and vitamin D- resistant rickets in children, and osteomalacia in adults. There is increased intestinal calcium absorption and urinary calcium excretion, while urinary phosphate excretion is diminished.

Food sources; Milk and milk products (except their fatty parts, such as cream, butter and ghee), beans, carrot, cauliflower, peas, potato, banana, mushrooms, peanut, fish, cauliflower, lima beans Eggs, pork, lamb liver. Pumpkin seeds are rich in phosphorus and increase urinary phosphate excretion.

Toxicity Levels; can induce an increased fecal excretion of calcium, possibly resulting in a calcium deficiency, can cause diarrhea and calcification (hardening) of organs and soft tissue, and can interfere with the body's ability to use iron, calcium, magnesium, and zinc.

Recommended dietary allowances (RDAs) for dietary phosphorous are listed below. Most people do not need to take phosphorus supplements.

Pediatric

• Infants 0 - 6 months: 100 mg daily
• Infants 7 - 12 months: 275 mg
• Children 1 - 3 years: 460 mg
• Children 4 - 8 years: 500 mg
• Children 9 - 18 years: 1,250 mg

Adult

• Adults 19 years and older: 700 mg
• Pregnant and breastfeeding females under 18 years: 1,250 mg
• Pregnant and breastfeeding females 19 years and older: 700 mg

Possible Interactions

Alcohol ; Alcohol may leach phosphorus from the bones and cause low levels in the body.

Antacids; Antacids containing aluminum, calcium, or magnesium (such as Mylanta, Amphojel, Maalox, Riopan, and Alternagel) can bind phosphate in the gut and prevent the body from absorbing it. When these antacids are used long-term, this can lead to low phosphate levels (hypophosphatemia).

Anticonvulsants; Some anticonvulsants (including phenobarbital and carbamazepine or Tegretol) may lower phosphorus levels and increase levels of alkaline phosphatase, an enzyme that helps remove phosphate from the body.

Bile acid sequestrants; Bile acid sequestrants are drugs that lower cholesterol. They can decrease the oral absorption of phosphates from the diet or from supplements. Oral phosphate supplements should be taken at least 1 hour before or 4 hours after these drugs. Bile acid sequestrants include:

• Cholestyramine (Questran)
• Colestipol (Colestid)

Corticosteroids; Corticosteroids, including prednisone or methylprednisolone (Medrol), may increase phosphorus levels in the urine.

Insulin; High doses of insulin may lower blood levels of phosphorus in people with diabetic ketoacidosis (a condition caused by severe insulin insufficiency).

Potassium supplements or potassium-sparing diuretics; Using phosphorus supplements along with potassium supplements or potassium-sparing diuretics may result in too much potassium in the blood (hyperkalemia). Hyperkalemia can be a serious problem, resulting in life-threatening heart rhythm abnormalities (arrhythmias). Potassium-sparing diuretics include:

• Spironolactone (Aldactone)
• Triamterene (Dyrenium)

ACE inhibitors (blood pressure medication); Drugs called angiotensin-converting enzyme (ACE) inhibitors, used to treat high blood pressure, may lower phosphorus levels. They include:

• Benazepril (Lotensin)
• Captopril (Capoten)
• Enalapril (Vasotec)
• Fosinopril (Monopril)
• Lisinopril (Zestril, Prinivil)
• Quinapril (Accupril)
• Ramipril (Altace)

Other drugs; Other drugs may lower phosphorus levels. They include cyclosporine (used to suppress the immune system), cardiac glycosides (digoxin or Lanoxin), heparins (blood-thinning drugs), and non-steroidal anti-inflammatory drugs (such as ibuprofen or Advil). Salt substitutes also contain high levels of potassium and may lower phosphorus levels if used long-term.