Can Dog Food Have Too Much Protein?

Of all the nutrients in dog food, protein is the one that gets the most attention. We know it’s crucial to dogs’ development and lives. But can you have too much of a good thing?

The Dog Food Advisor’s nutritionist, Laura Ward, discusses the highs and lows of protein in dog foods — and how much is too much.

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If you’ve checked out the AAFCO Nutrient Profile, you’ll know that the minimum protein requirement for adult dogs is 18% and for puppies it’s 22.5%. This is expressed on a “dry matter basis” or DM, a way to compare foods of different moisture (such as a wet food and a dry food) by theoretically removing the water content.

However, there’s currently no nutritional maximum for protein — so what does that mean for our dog’s food? How much protein is too much?

How high is high-protein?

We consider any diet with a DM crude protein content of more than 28% is high-protein. It isn’t unusual, however, to see protein levels above 35%, or even over 40% in dry foods. In fresh and wet foods this is often greater, at around 60% DM. This high protein bracket, therefore, covers a wide range of protein possibilities.

Benefits of high protein in dog food — and when to be cautious

Protein is linked to palatability for dogs, so high-protein foods are usually super tasty. Dogs will often choose a high-protein food over a lower-protein option, so if you have a fussy eater, high-protein food can be a great choice. There are other scenarios too where higher protein is particularly valued.

For active or working dogs, the protein they need for maintenance is increased. Not only is there a greater need for the replenishment of muscle tissues, but other changes in the body require proteins from the diet too. This is because endurance activities require more efficient delivery of oxygen and nutrients to muscles, which the body becomes conditioned for, just like with human athletes.

These changes include increased blood volume, red blood cell quantity, and increases to other parts of the body cells used for energy generation. The protein building blocks for this come from increased protein being delivered through the diet.

It’s also important for senior dogs to have a high-quality source of protein in their diet. Protein, making up a larger proportion of the calories in a senior diet, can support their lean muscle and help to avoid the muscle-loss associated with ageing. Moderate- to high-protein wet or fresh food options can be good choices for senior dogs, as they improve hydration, are very palatable, and are also soft on weaker teeth.

Weight-loss is another situation where protein is important. The energy (or calorie) content of the food is carefully controlled to aid weight loss, but it’s also important to support muscle. A good quality protein supply and higher-protein content in the diet is essential to avoid muscle wastage.

However, dogs are more likely to eat more of a high-protein diet, which is counterproductive for weight loss. High-protein diets at the higher end of our high protein range (more than 35% DM) are often particularly nutrient dense and can be ill-suited for weight loss. Dogs need only a small quantity of these foods which, when combined with weight loss measures, can leave dogs fed a high-protein diet which isn’t designed for weight loss, feeling hungry.

For pregnant and nursing dogs, protein is a crucial element of the diet. During these phases, the requirement for proteins, through changes to the body and the development of puppies or the supply of milk, is great. AAFCO’s nutritional profile for growth is most suitable for pregnant and nursing dogs, to represent this increased requirement. High-protein foods can be a great choice during this time.

With diabetic dogs, it’s the carbohydrate content of food which is the greatest focus. As diabetic dogs cannot safely regulate their response to blood sugars, carbohydrates should be limited in the diet. This generally means that energy is primarily supplied by fats and proteins in the diet to minimise peaks and falls in blood sugar after meals. High-protein and low-carbohydrate foods are recommended, but your veterinarian will advise further what this looks like for your dog’s diet.

In the case of any susceptibility to kidney problems, or renal insufficiency, take advice from your veterinarian before feeding a high-protein diet. Although it’s important for dogs with renal insufficiency to still have a high-quality source of protein in their diet, diets which contain a moderate, rather than high, protein content are often more suitable.

Studies have shown that protein is not connected to the progression of chronic renal failure, however, recent studies have also found high protein (46%) can be linked to an increase in markers of kidney dysfunction. Although veterinary advice now doesn’t call for protein restriction, it often recommends avoidance of excessive dietary protein.

What’s wrong with low-protein dog foods?

A real low-protein diet is only available when prescribed by a vet, as feeding a low-protein diet without medical need could cause deficiency diseases in a healthy dog. There are foods, however, which meet AAFCO protein requirements without supplying very much extra protein. These foods supply the majority of the energy from fats and carbohydrates.

This is often associated with lower quality or cheaper foods, as protein is often a key driver of cost in a dog food recipe. As protein is linked to palatability in dogs, lower protein foods can be less tasty.

Carbohydrates are broken down differently to proteins, into sugars. The carbohydrate source in the recipe determines how the blood sugar is affected. For foods which are high on the Glycaemic index, a peak, followed by a fall in blood sugar is seen. Although not an area which has been sufficiently studied, this is thought to be linked to fizzy and lethargic behaviour – like children fed sugary foods.

Summary — how important is protein in dog food?

The quality of the protein in a food is far more important than the quantity. A protein source which supplies all of the amino acid protein building blocks in the correct quantities and in a digestible and accessible form is the goal.

There are certainly benefits to be gained by supplying high levels of protein in a dog’s diet, but the effects of some of these super-high-protein foods are not well studied yet. If in doubt, feeding a moderately high protein food to begin with — of 28% to 30% DM protein — and monitoring your dog’s reaction is recommended. Remember, you can always ask your vet about changes to your dog’s diet.