Phosphate is a mineral found in food and is essential for healthy bone formation. It is the second most abundant mineral in the body, representing 1% of the total adult body weight or 25% of the total mineral content of the adult body.
During kidney failure, the kidneys cannot excrete phosphate sufficiently and it accumulates in the blood. This causes calcium to leak from the bones, and leads to weak bones that are more likely to break. It may even damage the kidneys, other organs, and may cause the skin to itch. For these reasons, patients with chronic renal failure must restrict the intake of phosphate through the diet.
It is very important to consult with a doctor or dietitian to prescribe the correct diet and to incorporate the information obtained from this article into the diet. They will prescribe the amount of phosphate to be consumed per day based on the kidney function, urine output and individual factors such as body weight, activity levels and the background diet.
Food sources of phosphate
Phosphate is widely distributed in food - generally good sources of protein are also good sources of phosphate. Dairy products and animal products like meat, poultry, fish and eggs contribute 60% of dietary phosphate in a mixed diet. Cereals and legumes contribute another 20% of dietary phosphate in a mixed diet.
Whole grains and whole grain flour contain phosphate in the form of phytate or phytic acid, which form insoluble compounds with other minerals in the diet like calcium, iron and zinc, thus reducing their absorption. Vegetables and fruit contribute about 10% of dietary phosphate in a mixed diet.Phosphate food additives are widely used by the food industry in baked goods, cheeses, processed meats and cold drinks.
Foods high in phosphate
Drinks made with milk.
Baked deserts or dishes containing milk, eggs and cheese e.g. milk tart, custard, macaroni and cheese.
Dried beans, peas, lentils, peanuts and soya products.
Nuts: all types.
Salty spreads like meat and vegetable extracts.
Bran flakes, Muesli (note that the inclusion of dry cereals usually require more milk to be used which is high in phosphate).
Chocolates and chocolate sweets with nuts, toffee, raisins, and dark chocolate.
Large amounts of dried fruit.
Dark cold drinks like beer and cola.
General nutrition recommendations for patients with chronic renal failure
In patients with chronic renal failure, phosphate intake should be limited to 800 – 1000 mg/day. To decrease dietary phosphate intake, patients are advised to:
- Restrict milk intake to 1 portion (½ cup) per day.
- Restrict high phosphate meats to 1 portion or 30g (matchbox size) per day and rather eat more of the low phosphate foods as prescribed by the dietician.
- Avoid or limit processed meat and dark cold drinks.
- Medication used to bind phosphate from the diet so that it is excreted in the stool, has to be taken with meals and not between meals.
(Acknowledgement: RenalSmart Nutritional Information System. Low Phosphate Diet. References from the scientific literature used to compile this document are available on request.
For further, personalised and more detailed information, please contact NICUS (e-mail: firstname.lastname@example.org or phone 021-933 1408) or contact a dietician registered with the Health Professions Council of South Africa.
- (NICUS, Health24, June 2010)
Your guide to renal nutrition