Some say that diets that are too high in protein can cause kidney disease in dogs. Is this true, and does that mean a raw diet might be dangerous for your dog?
If you asked this question in a raw feeding forum or group, you might receive some responses that aren’t quite true. For example…
Raw diets are low protein.
TRUTH: Raw diets are high in protein on a dry matter basis.
Raw meat is very high in moisture: about 75%, give or take. So on an as fed basis, a raw diet’s % protein will be lower, and the % moisture will be higher.
But pet foods are always analyzed on a dry matter basis, because it is a better representation of the actual nutrient content of the food. Moisture content does not affect the total number of grams of protein or number of calories an animal is consuming when they eat a meal.
In other words, the added water weight in raw artificially lowers the protein percentage. Here’s an example: Let’s say a 100 gram raw chicken breast has 20 grams of protein and is 20% protein. If you cook it, it still has 20 grams of protein but is now 40% protein because it has lost moisture and weights less. If you dehydrate it, now only weights 30 grams and it still has 20 grams of protein, but it is now 80% protein because nearly all the water has been removed.
The problem with comparing foods based on percentage is that the water content, which is an empty filler (contributes no nutrient value to the food), varies greatly. When analyzing and comparing foods, we want to see the actual nutrient content of the food, regardless of the moisture content – and that’s why we analyze them using the dry matter basis. When converted to a dry matter basis, raw diets are very high protein.
“To make meaningful comparisons of nutrient levels between a canned and dry product, they should be expressed on the same moisture basis.” – US Food and Drug Administration, Pet Food Labels – Guaranteed Analysis 
To convert a food from “as fed” to a dry matter basis, there is just some simple math involved. First, subtract the moisture % from 100. Then divide the % protein of the food by that number, and multiply your result by 100.
Let’s convert raw 80/20 ground beef to a dry matter basis as a quick example. According to the USDA nutrient database , it has 62% moisture (water) and 17% protein (rounding numbers as needed). 100 minus 62% moisture equals 38% dry matter. Then we divide 17% protein by 38, which equals about 0.447. Multiply that by 100 and you get 44.7%, which could be rounded up to 45% protein on a dry matter basis.
Here is a table of the protein content on a dry matter basis of some common raw food ingredients, popular kibble products, and popular commercial raw products for comparison.
How much is too much?
We’ve discovered that the raw 80/20 ground beef that we analyzed is 45% protein on a dry matter basis… but what does that mean?
An adult dog’s recommended protein requirement according to NRC guidelines is 25%. According to AAFCO, the minimum protein for adult maintenance is 18%, and the minimum protein for growing puppies or breeding animals is 22%. However, neither NRC nor AAFCO list a maximum protein allowance .
So then where did the idea that high protein diets cause kidney issues come from? A study in 1942 hypothesized a correlation with high protein diets and decreased renal function in dogs . There have also been other studies that demonstrated a potential link between high protein diets and kidney issues , however, these studies were done primarily on rats, not dogs … and dogs have significantly different dietary needs than rats.
The theory behind the hypothesis that high protein diets can cause kidney disease stems from the idea that since the kidneys would have to filter more waste products associated with protein metabolism (such as nitrogen), the extra stress of this hyperfiltration could cause eventual deterioration of the kidneys, leading to renal disease and kidney failure. However, other studies have questioned this hypothesis, instead concluding that hyperfiltration by the kidneys is simply a normal adaptive mechanism that is not associated with decreased renal function .
In fact, multiple studies on high protein canine diets have shown no adverse effect on kidney function in healthy dogs [8, 9], and some show that high protein diets may be beneficial rather than harmful . One study stated, “Results of this study indicated there were no adverse effects from the high protein diet and mortality was actually higher in the low protein group” .
In dogs that have been diagnosed with kidney disease, a low protein diet may be recommended by your vet. However, it hasn’t necessarily been proven that a lower protein diet will slow the progression of kidney disease.
“The effect of protein restriction on the progression of renal damage in dogs and cats remains controversial and no definitive study exists on this matter.” – UC Davis Veterinary Medicine, Nutritional Management of Chronic Renal Disease 
Instead, rather than the amount of protein, it is better to look at the quality of the protein in a dog’s diet.
Protein quality matters
The bioavailability of the protein in the diet is a big factor in a dog’s ability to metabolise that protein effectively. A protein’s biological value is determined by the efficiency in which the amino acids can be utilized by the dog. Animal derived protein sources are generally of higher biological value to dogs than plant derived sources. Processing can also have an adverse effect on protein quality. A highly digestible source of quality protein will be much easier for a dog to metabolize into amino acids, placing significantly less stress on the kidneys.
Moisture content in raw diets
One benefit of raw diets is its high moisture content. While we might calculate the moisture content out when finding a food’s dry matter basis, that doesn’t mean moisture is completely useless. It is well documented that high dietary moisture is beneficial for excretory health [14, 15]… including kidney function!
Is a raw diet too high in protein for dogs? The answer is no: a raw diet is high in protein, but it is bioavailable, highly digestible protein that is easy for dogs’ bodies to break down into amino acids.
If your dog has renal disease and your vet has recommended a low protein diet, I recommend consulting with a canine nutritionist that can determine if your dog truly needs a low protein diet or if a raw diet is suitable for your dog. If a raw diet is still too high in protein, there are still better options than kibble: a nutritionist can design a suitable homemade diet recipe for your dog’s needs.