Phosphorus in the Progression of Kidney Disease

If you’ve read many of my blog posts or heard me speak then you probably know that I think phosphate additives are a serious concern for kidney patients at all stages of chronic kidney disease. It’s been long established that high levels of phosphorus are a sign of bone and mineral disorder in CKD patients but that doesn’t tell us the whole story.

A study published online in the Journal of the American Society Nephrology (JASN) ( showed that that patients with high phosphate levels developed kidney failure faster than those with low phosphate levels. They also showed that high phosphate interfered with kidney medications. This is just one of several recent studies that support the idea that phosphate plays a role in the progression of CKD and is much more than a complication of the disease.

Phosphorus in our food is a confusing subject. The phosphorus in meat and dairy is much more easily digestible than that in plant proteins, but generally about 40-60% of naturally-occurring phosphorus is absorbed. Phosphates from food additives however are estimated to be absorbed at over 90% and some studies suggest we get as much as 1000mg/d in the average diet.

So what does this mean for CKD patients or those people at risk for CKD? Well I think that even if your blood levels of phosphorus are normal, it’s a very good idea to avoid foods with phosphate additives. The phosphorus in these foods is extremely well absorbed and is generally found in products that are processed, high in salt and are of low nutritional value. Unlike sodium, phosphorus is not found on the nutrition facts table so it’s very hard to figure out exactly how much phosphorus is in a food product. And, because they are a food additive, phosphates may be listed anywhere in the ingredients list (not necessarily in order of amount).

Phosphate additives are added to foods for many reasons including as a leavening agent, a preservative, and a flavour enhancer. Baking powder is a source of phosphate that you may have in your pantry.

Unfortunately there is no easy list of foods containing phosphate additives so you have to read the labels.

Read the ingredient list and look for variations of the word “phosphate” (all contain PHOS) such as:

  • PHOSphoric acid
  • Sodium PHOSphate
  • Monocalcium PHOSphate
  • PolyPHOSphate
  • PyroPHOSphate
  • Sodium hexametaPHOSphate

Typically you will find phosphates added to:

  • Processed cheeses, spreadable cheeses or slices
  • Colas
  • “Seasoned” meats, poultry and seafood including most processed and deli meats.  Read labels carefully since these meats may appear in your fresh meat counters at local grocery stores.
  • Frozen meats, fish, chicken breasts
  • Bakery products such as biscuits, muffins and snack cakes
  • Non-dairy creamers

When cooking at home you can easily substitute baking soda and cream of tartar for baking powder to lower the phosphorus in your homemade items:

Substitute 1 tsp baking powder with 1/4 tsp baking soda + 1/2 tsp cream of tartar

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