Proteins

Some say that diets that are too high in protein can cause kidney disease in dogs. Is this true, and does this mean that a raw diet can be dangerous for your dog?

If you asked this question in a raw food forum or group, you might get some answers that aren't entirely correct. For example...

MYTH: Raw diets are low in protein.
TRUTH: Raw diets are high in protein on a dry matter basis.
Raw meat has a very high moisture content: about 75%, give or take. So on a per-meal basis, the % protein in a raw diet 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 the number of calories an animal consumes when eating the food.

In other words, the added weight of water in raw food artificially lowers the protein percentage. Here's an example: Let's say 100 grams of raw chicken breast has 20 grams of protein and is 20% protein. If you cook it, it still has 20 grams of protein, but it's now 40% protein because it's lost moisture and weighs less. If you dehydrate it, it now weighs only 30 grams and still has 20 grams of protein, but it's now 80% protein because almost all of the water has been removed.

The problem with comparing foods based on percentage is that water content, which is empty filler (does not contribute to the nutritional value of the food), varies greatly. When we analyze and compare 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 a dry matter basis. When converted to dry matter, raw diets are very high in protein.

“To make meaningful comparisons of nutrient levels between canned and dry products, they must be expressed at the same moisture content.” - U.S. Food and Drug Administration, Pet Food Labels - Assured Analysis [1]

To convert a food from "fed" to a dry matter basis, there's just some simple math involved. First, subtract the % moisture from 100. Then divide the % protein in the food by that number and multiply your result by 100.

Let’s convert 80/20 raw beef to dry matter as a quick example. According to the USDA Nutrient Database [2], 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 can 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 weight loss products, and popular commercial raw products for comparison.

protein content chart
How much is too much?
We found that the 80/20 raw beef we analyzed was 45% protein on a dry matter basis... but what does that mean?

The recommended protein requirement for adult dogs according to the NRC guidelines is 25%. According to AAFCO, the minimum protein for maintenance of adults is 18%, and the minimum protein for raising puppies or breeding stock is 22%. Neither the NRC nor the AAFCO specify a maximum amount of protein [3].

So where does the idea that high-protein diets cause kidney problems come from? A 1942 study hypothesized a correlation between high-protein diets and reduced kidney function in dogs [4]. There are other studies that have shown a potential link between high-protein diets and kidney problems [5], but these studies were mostly done on rats, not dogs [6] ... and dogs have significantly different nutritional needs than rats.

The theory behind the hypothesis that high-protein diets can cause kidney disease stems from the idea that since the kidneys will have to filter more waste products associated with protein metabolism (such as nitrogen), the additional stress from this hyperfiltration could lead to eventual deterioration of the kidneys, leading to kidney 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 reduced kidney function [7].

In fact, numerous studies of high-protein canine diets have shown no adverse effects on renal function in healthy dogs [8, 9], and some have suggested that high-protein diets may be more beneficial than harmful [10]. One study stated, “The results of this study indicate that there are no adverse effects of the high-protein diet and mortality was actually higher in the low-protein group” [11].
For dogs that have been diagnosed with kidney disease, your veterinarian may recommend a low-protein diet. However, a lower-protein diet has not necessarily been proven to slow the progression of kidney disease.

“The effect of protein restriction on the progression of renal injury in dogs and cats remains controversial, and there is no definitive study on this issue.” - UC Davis Veterinary Medicine, Nutritional Management of Chronic Kidney Disease [12]

Instead, rather than the quantity of protein, it is better to look at the quality of the protein in your dog's diet.

Protein quality matters
The bioavailability of protein in the diet is an important factor in a dog's ability to metabolize that protein effectively. The biological value of protein is determined by the efficiency with which the amino acids can be utilized by the dog. Animal protein sources generally have a higher biological value for dogs than plant-based sources. Processing can also have an adverse effect on the quality of the protein. A highly digestible source of quality protein will be much easier for the dog to metabolize into amino acids, placing significantly less stress on the kidneys.

Protein biological values ​​of various ingredients for dogs [13].
Moisture content in raw diets
One advantage of raw diets is the high moisture content. Although we can calculate moisture content when we find the dry matter basis of a food, this does not mean that moisture is completely useless. It is well documented that high dietary moisture is beneficial for excretory health [14, 15] ... including kidney function!

Conclusion
Is a raw diet too high in protein for dogs? The answer is no: a raw diet is high in protein, but it is a bioavailable, highly digestible protein that can be easily broken down into amino acids in dogs' bodies.