I am aware of the importance of a cat needing protein, but not sure which brands of food to use when a cat has renal problems. I have been using the prescription diet can food, but not confident with them meeting protein needs. I have been told to restrict protein, but then to look for "good sources" of protein. How do you determine "good protein source" for a cat with rental insufficiency? (I have been giving my cat subcutaneous fluids as well) Thanks.
Hi DTB, really if your goal is to slow down progression of kidney disease, your best bet is a prescription diet.
The level of protein restriction that’s necessary in kidney disease does depend on the stage of disease. Early stages of chronic kidney disease (essentially IRIS stages 1-2) actually do not require significant protein restriction to the degree that stages 3 and 4 would need. This has been a more recent understanding in the last 3-4 years and has led to the development of early kidney care prescription diets that are not severely protein restricted but instead have moderate restriction.
One of the most important components of dietary therapy for CKD at any stage is phosphorus restriction. You can read more on phosphorus in cat foods in our article here.
To me, phosphorus is the biggest concern about choosing a prescription diet vs. an OTC diet or even formulating one at home. You can get an idea of protein content in almost any diet. All commercial diets will indicate what the minimum phosphorus level is, in order to meet AAFCO guidelines for nutrient minimum requirements. However, there is no established maximum phosphorus level that manufacturers are required to follow.
Thus, with some exceptions, the only commercial diets by and large that show the maximum phosphorus level in the diet are prescription kidney diets.
In terms of home-prepared diets, it’s really hard to develop high quality protein diets for cats that are also restricted sufficiently in phosphorus. Organ meats and anything containing cartilage and bone (like some raw diets) are high in phosphorus. Without a way to accurately measure the nutrient content of a homemade diet, the phosphorus content is a total guess.
Getting back to protein restriction. If you do have a cat in stage 3 or 4 where heavier protein restriction is necessary, it’s not just looking at percentages. It’s also about the protein quality. Commercial diets can include particular amino acids (the building blocks of protein) to shape a nutrient profile and ensure a cat is getting the most nutrient value out of the protein present. Here is a link for an article written by two veterinary nutritionists on the topic of protein restriction with kidney disease. Towards the end, they do cover the topics of nutritional adequacy of protein levels in prescription kidney diets (which was one of your main concerns), as well as considerations with home-prepared and raw diets. While I realize the article is on Royal Canin’s website, which makes a prescription diet, the article is very well-written, well referenced, and informative. The authors can also explain some of the nuance of the dietary protein debate a bit better than I can.