Focusing on Protein in the Diet


PetMD Editorial

Published Mar. 2, 2011

By T. J. Dunn, Jr., DVM

Protein requirements of dogs is an important and often misunderstood aspect of pet nutrition. "You are what you eat" is a saying we've all heard and it surely has some truth to it.

Every responsible dog owner I’ve talked to has real concern about feeding a high quality diet to his or her dogs. Remarkably, though, no two dog owners seem to agree as to which dog food is “the best”. A large part of the disagreement regarding “the best” food to feed centers on the often ambiguous, mysterious and sometimes incorrect information we all see regarding the substance we call protein.

Let’s get the facts straight about the importance of protein in the dog’s diet. Then we can better judge which food would be “the best” for own dogs.

Unlike felines (go here to see some of the differences between feline and canine metabolism) dogs are classified as omnivores. They can survive on a diet of either plant or animal origin if it is balanced and diverse. But to thrive and not merely survive, dogs should have a source of animal protein -- MEAT! -- in their diets.

There is a huge difference between survive and thrive! Nature made the rules of biochemistry and nutrition and we mortals have no power (and no business, for that matter) to try to bend those rules. For that reason there are truly no adequate vegetarian diets for cats. For that reason dogs thrive on diets based on meat.

Every single day in practice I see dogs that are not thriving because nature's rules are not being followed. Overweight dogs, dogs with itchy, flaky skin, dogs with coarse and brittle coats, dogs with poor energy levels and resistance to infection -- 95 percent of the time these dogs will be consuming diets low in animal origin tissues and high in grain-based products. Inexpensive, corn-based diets are some of the worst.

Meat by-products:  heart, liver, spleen, intestines (emptied of their contents), blood, kidneysGrains...  corn, wheat, rice, barley, soybeans, oatmeal
LambFiber...  The non-digestible cellulose parts of plants such as peanut hulls
BeefNuts and seeds
Fish... salmon, herringFruits
Poultry... chicken, turkey, duckVegetables
Dairy...  eggs, milk, cheeseLegumes

Dogs need meat! Dogs thrive on meat-based diets. (Caution: an ALL meat diet is hazardous too!) Dogs can and do assimilate grains such as corn, barley, oats, wheat and soybean meal. Remember, though, that grains provide mostly carbohydrates and only limited amino acid (protein) profiles. Extra carbohydrate intake, above the immediate needs of the dog (which occurs often with grain-based diets) prompts internal enzyme factors to store that extra carbohydrate (sugar) as fat.

Give that same dog extra protein and it is excreted through the kidneys and NOT stored as fat. Knowing this, what do you think would make a better "weight loss diet" for a dog ... one with grain as the main ingredient or one with a protein-rich meat source as the main ingredient?

Ahhhhhh ... I know what you're thinking! Too much protein! Kidney damage! Well, guess what? The very early research that pointed a finger at protein as being a cause of kidney failure in dogs wasn't even done on dogs! It was done on rats fed unnatural diets for a rodent -- diets high in protein. (Were we tinkering with Nature during these “tests”?) Rats have difficulty excreting excess protein in their diets because they are essentially plant eaters, not meat eaters.

Dogs are quite able to tolerate diets with protein levels higher than 30 percent on a dry weight basis. Dogs are meat eaters; that's how Nature made them! Rats are not. So some of the early research on rats was assumed to be true for dogs ... and the myth of "too much protein in a dog's diet causes kidney damage" was started. And just like any seemingly valid rumor or assertion, it derived a life of its own and is only recently being accepted as untrue.

Here is just one of many references that recently have appeared asserting the lack of data indicating that reducing the protein level in a food helps to protect the kidneys:

"...restriction of protein intake does not alter the development of renal lesions nor does it preserve renal function. Considering these (research) findings, the authors do not recommend reduction of dietary protein in dogs with renal disease or reduced renal function in order to achieve renoprotective effects."
-Kirk's Veterinary Therapy XIII, Small Animal Practice, page 861, written by Finco, Brown, Barsanti and Bartges

They do recommend, though, that once a Blood Urea Nitrogen (BUN) level reaches 75, which is very elevated, that some restriction of protein intake be considered for beneficial effects unrelated to kidney function dynamics. These authors point out that phosphorus blood levels can play a major role in the health status of dogs with compromised kidney function.


Here's another expert opinion:

"The dog can digest large amounts of proteins, especially those of animal origin" stated Prof. Dominique Grandjean DVM, Ph.D., at the Fourth Annual International Sled Dog Veterinary Medical Association Symposium (page 53 of 1997 PROCEEDINGS).

Current, and even ignored thirty-year-old research by Dr. David S. Kronfeld and others, spells out the evolutionary need for canines to have sources of high quality protein such as is found in animal tissues. Meat (muscle tissue), organ tissues such as liver, kidneys, spleen, and heart are particularly rich in the complex molecules called amino acids that end up as protein.

There are 22 amino acids involved with the dog’s metabolism and of these the dog requires 10 different amino acids to be supplied by the diet. The other 12 required amino acids can be manufactured internally in the dog’s liver. Grains tend to be better sources of carbohydrate, a quick source of energy. Animal-derived tissues are more easily digestible and have a more complete array of amino acids than do grains.

Meats and meat by-products (meat by-products are blood and organ tissues and do not include hide, hair, hooves and teeth) are exceptionally high quality protein sources for dogs. (That’s right! Meat by-products are excellent sources of nourishment for dogs. By-products do not contain floor sweepings, old flea collars, gasoline or machine parts. We all need to have an open mind and take a look at what by-products really are.)

"But too much protein is bad, right?" you ask. Do your own research and poll half a dozen nutrition specialists (not the guy who runs the local pet shop) and here is what you will find: There is no general agreement among expert nutritionists regarding what constitutes “too much” protein in the dog’s diet. Research shows that dogs have a high capacity for digesting and utilizing diets containing more than thirty percent protein on a dry weight basis. (Dry weight basis means the food with no moisture present. Dry dog food in a bag usually has 10 percent moisture and canned food has about 74 percent moisture.) If left to catch and consume prey to survive, as wild canines do every day, dogs’ diets would be even higher in protein than what is generally available commercially.

Think about it ... do you ever see a stray dog grazing in a corn or bean field to allay its hunger? Nature has created a meat-eating machine in the dog and every day in practice I see the health benefits displayed by the feeding of meat-based diets.

Dogs fed poor quality diets look and feel great only if their caretakers also feed table scraps such as chicken, meat, eggs, cottage cheese and other “left-overs.” Meat such as chicken, poultry, beef or fish should be the first ingredient listed in any dog food you judge to be "the best".

"But what about the older pet?" you might ask. "I’ve always been told that high protein diets are bad for an older dog's kidneys; even my veterinarian says so." What researchers have proven is this: In dogs that actually have kidney damage or dysfunction (regardless of their age) and that have a BUN level greater than 75, restricted protein intake may be beneficial but not because of any adverse impact on the kidneys. The protein these impaired dogs ingest should be of high quality such as is derived from eggs, poultry, and meat. On the other hand, high protein levels in a food DO NOT cause kidney damage in the normal, healthy dog or cat!

So what does that mean for the older dog? It means that you should not restrict feeding high quality protein to older dogs just because they are older. There is even some valid research that indicates older dogs may need a higher percentage of protein in their diets than they required during middle age. This shouldn’t be a surprise to us because dogs evolved through the ages as meat eaters. The grain-based diets for dogs did not even exist until seventy years ago when we humans demanded the convenience, simplicity and economy of dog food in a bag.

The bottom line is this, and it is based on fact -- protein intake does not cause kidney damage in healthy dogs or cats of any age. So whatever you choose as “the best” diet for your dog, make certain that an animal tissue source is listed first in the ingredient list.

Your older dog or cat should, if its kidney function is normal, receive the benefits of a high quality diet rich in animal-derived protein. For an excellent source of easily understood nutrition principles consider purchasing Canine and Feline Nutrition, by Case, Carey and Hirakawa.


Protein and Hyperactivity

Most dog caretakers at one time or another have heard this pronouncement: "High protein diets can make dogs hyper!"

I have searched the literature and contacted nutrition specialists regarding this myth and nowhere can I find any scientific study that proves this unfounded contention. There are no biochemical or nutritional factors that would even make this supposition appear to be credible.

Hyperactivity in dogs has numerous potential motivators, including genetic temperament predispositions, but a link between high levels of protein in a dog's diet and hyperactivity has yet to be proven.

I listened to a canine "expert" once tell me that Purina Hi Pro was causing hyperactivity in dogs and that he's seen it happen. I politely pointed out that Purina Hi Pro is in fact not high in protein at all ... and yet the myth goes on.

Feed your dog a high quality, meat-based diet and, just as nature set things up, your dog will thrive. Fear not the feeding of protein.

Image: doggybytes / via Flickr

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