Old dogs need more protein, not less
so why are vets prescribing low-protein kibble?
Happy New Year! We hope that you are having a great start to your new year. After the holiday rush (and the entire hectic 2025) we were totally drained and have taken a much needed break. Time to get back to work!
Vets often prescribe low protein diets to dogs with kidney and liver disease, and these are usually older dogs. The science suggests this may not be the right move. Today we share the research and how low protein diets became so popular. Also we include a couple of balanced senior meals that we rely on for our senior dogs.
Disclaimer: This post is for informational and entertainment purposes only. We share our interpretation of multiple scientific studies. In no way are we providing medical advice. Please consult a reputable health care provider for specific conditions.
What is protein exactly?
Protein is one of the three macronutrients. The other two are fat and carbohydrates. These three nutrients make up the calories or energy that a food contains. But energy is only a crude measure, how animals use these nutrients is even more important.
In dogs and humans, protein is not a good energy source. We prefer to use proteins to make tissues that do things. For example, muscle is mostly made from proteins. Other structures like the hemoglobin in blood cells that moves oxygen around our bodies and insulin that helps digest carbohydrates (technically a peptide hormone) are both proteins.
When dogs and people don’t consume enough protein, their bodies break down muscle to cover protein needs. This happens EVEN IF THEY CONSUME ENOUGH CALORIES from fat and carbohydrates! This is why protein consumption is a hot topic, especially because when animals age, they lose sensitivity to protein and need more. The result is age related muscle loss, called sarcopenia. See our post on protein.
Kidneys and low protein diets
The evidence on low protein diets helping renal function is very thin. Especially since renal issues are associated with older dogs, where high blood sugar, muscle loss and gum disease are all more likely to occur. Carbohydrate heavy diets are likely to be even more problematic. More on that below.
In multiple studies on low protein diets, researchers conclude that low protein had no effect on renal function improvement. The improvements came from reducing phosphorous.
Phosphorous is an essential mineral. But in dogs that have kidney disease it can build up over time. Bone meal, which is often used in kibble, is one of the highest phosphorous containing foods. Other foods that are high in phosphorous include organ meats like liver and kidney, fish with bones, and hard cheeses. Also, many processed foods (like kibble) use phosphate salts as preservatives.
Low phosphorous diets consists of reducing high phosphorous foods and replacing them with lower phosphorous foods like egg whites, rice, and sweet potatoes. Upping fat intake (50-60% of calories), so less calories come from phosphorous containing foods can also be helpful.
What about kidney stones?
Oxalates, found in foods like spinach and beets, are often blamed for causing stones in dogs, but the research suggests that it’s not the cause. The highest risk factor for kidney stones is high blood sugar. In one study, just 1 mmol / liter increase in blood sugar increased the risk of kidney stones by 39 times! To put this in perspective 1 mmol of glucose in a liter of water is less than a drop of pure glucose in a cup of water.
Since carbohydrates all break down into glucose, the major contributing factor for having stones is likely kibble consumption in dogs at risk for kidney stones. Genetics appear to play a large role because certain breeds, like the Miniature Schnauzer, are most at risk to develop stones.
How we approach senior diets
Since AAFCO does not publish guidelines for seniors nor renal diets, the formulations from pet food makers are highly variable. Many even add salt to cause thirst and dilute urine. Since kibble must be about 40% or more carbohydrate by weight, reducing protein usually means the formulation is high carbohydrate.
One of our family dogs, Rocky, was recommended a low protein diet by a vet last year. Before we made any changes we did a deep dive of the literature around low protein and senior diets and shared that with all of you. This deep dive led us to dedicate a whole section to seniors in The Dog’s Table.
Rocky is now doing as well as ever, despite getting most of his teeth removed. He ate kibble for most of his life and had major tooth decay. We switched to real foods over two years ago and his health rapidly improved. Every time his food is being prepared he still runs to the kitchen at 16 years old.
Today his food contains about 50% fat, 40% protein and 10% complex carbohydrates. The food is blended into a smoothie and fed with added water. Here are two of his recipes.
Your dog has individual needs
Because every pup is different, adjusting recipes can help to dial in their health. Some dogs that are intolerant of carbs do well with grains removed. Other pups do well with slightly more carbs in their mix. When experimenting, we adjust the grain by 10% and see how their poop and general well being is affected.
Putting it all together
Protein is super important for normal bodily function in dogs and humans. Most longevity researchers and doctors stress higher protein consumption for people, especially as we age. Yet most vets recommend lower protein diets for dogs as they run into age-related issues. The literature just does not support this practice. Of course there are conditions that may need careful protein management, and we are not making any recommendations on those. Our opinion is that low protein diets are overused to the detriment of many of our best friends.
Thats it for this week.
All the best,
Joelle and R.A.