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The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Geriatric Pets Need More Protein

It is commonly believed that feeding geriatric dogs and cats normal or high amounts of protein can cause kidney disease or make existing kidney disease worse. Food manufacturers prey on this belief by offering lower protein foods for geriatric dogs and cats, when in actuality, geriatric pets benefit from higher protein diets.

In fact, the prolonged feeding of special veterinary kidney diets to pets without clinical signs of kidney disease can actually cause unnecessary muscle loss, a compromised immune system, and osteoporosis.

Why the Confusion?

Early studies in rats showed that kidney disease slowed when animals were fed lower protein diets. This research heavily influenced the thinking of the veterinary community despite the lack of research in dogs and cats that demonstrated the same results. The cause and progression of geriatric kidney disease and failure still eludes us.

What is true of low and ultra-low protein diets in animals with kidney failure is that it reduces the symptoms created by the disease. The metabolism of protein and amino acids produces ammonia. The liver converts this ammonia to a less toxic chemical called urea. Urea is then safely filtered from the blood into the kidneys and evacuated from the body in the urine. Animals with kidney disease have a decreased ability to rid the blood of urea. As blood urea nitrogen or BUN increases in the blood it causes other harmful chemical changes, reduces the appetite, and can even cause painful sores in the mouth that become infected and suppress appetite even further. The breath of animals with severe kidney disease actually smells like urine!

Feeding low or ultra-low protein diets reduces the amount of ammonia that the body must convert to urea. The lowered BUN decreases some of the other chemical changes, so clinically these pets feel better, their appetite improves, and their oral sores heal. The diet does not alter the severity of the kidney disease or the further progression of the disease; it only reduces the other symptoms associated with the disease.

Because advanced kidney failure is a fatal condition, the long term side effects of a low protein diet simply don’t matter. Comfort and quality, however long, is the goal. With cats this is particularly difficult, because they are less tolerant of low protein diets and will refuse to eat. Again, it is finding that right balance between symptoms and quality of life, not impossibly curing or slowing the disease.

Low Protein Problems

The effects of malnutrition generally occur over a long period of time. That is why feeding an older animal low protein food due to the mistaken notion of preventing kidney disease is a problem. Even animals with early indications of kidney disease (elevated BUN and creatinine, moderate increase in water intake), but without clinical signs, will probably live long enough to suffer the same malnutrition issues if put on these diets.

As animals and humans age they lose muscle tissue. This phenomenon is called sarcopenia. As muscle tissue mass decreases so does muscle strength. That is why old people are less steady or have difficulty catching their balance. Pets may show similar symptoms with changes in their movements and a reluctance to jump up or climb. Sarcopenia, especially in dogs, accelerates if the pet has arthritic or neurological conditions that limit activity. You can actually see the atrophy (shrinkage) of their muscles, especially in the hind limbs or along the spine.

Studies have shown that diets with higher levels of protein increases the percentage of muscle tissue and decreases sarcopenia in geriatric subjects. Feeding a low protein diet would do the opposite and increase muscle loss.

The cells of the immune system rely on ready sources of protein and amino acids to produce antibodies and other protective chemicals. Long term feeding of inadequate amounts of protein can decrease the speed and effectiveness the immune response. Geriatric patients are the very group that needs a strong, vigilant immune system.

When people think of bone they think of the calcium and phosphorus minerals. Few appreciate that the strength of bone is due to those minerals intertwined in a protein web. Much of bone tissue is actually protein. Without adequate protein for this web, bone cannot maintain its strength and density. Low protein diets can increase age related osteoporosis. It is sad to view osteoporotic bones in the X-rays of animals that have been on long-term low protein diets; animals that had no evidence of kidney disease or had only early indications of impending kidney disease.

The Take Home

Dietary protein levels do not cause or alter the course of kidney disease. Low dietary protein only decreases the symptoms associated with kidney failure, not slow it or cure it. Geriatric pets require the same or more protein than younger animals, especially active seniors. Old pets may be special, but not with regards to protein.

Dr. Ken Tudor

Image: Alan Wesley / via Shutterstock


Comments  10

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  • CRF
    07/05/2012 11:22am

    I've had several kitties with CRF (Chronic Renal Failure) and have struggled with finding the best food.

    Do you suggest that feeding "normal" amounts of protein until the critter is in the later stages of CRF and then using a lower protein to help alleviate symptoms?

  • 02/13/2013 09:06pm

    In the last week of September 2012, my long-haired Norwegian Forest cat, Jethro, aged 16, was diagnosed with kidney disease. The vet conducted blood tests and found out that the disease is not in an advanced stage. He recommended a daily dose of 5 mg of Fortekor and low protein diets to stabilize the disease.

    I bought Hill’s K/D and Royal Canin’s RENAL low protein diets. It’s a struggle to feed him. In the morning he eats a tablespoonful of wet food. Sometimes he sniffs the food, gives contemptuous look and walk away with majestic impertinence. I follow him, coax him to eat. In the night I feed him dry food. There is an increase in water intake. He has long hair and he enjoys brushing his hair. I brush him thoroughly five to six times a day. In spite of regular brushing he pulls his hair and swallows it. So in addition he has hairball in his stomach. In the evening I administer Fortekor.

    Before the kidney problem he enjoyed raw red meat, drank Whiskas catmilk and dry food. His weight was 5½ kg and now he weighs 4½. I noticed atrophy of his muscles, especially in the hind limbs or along the spine.

    You mentioned about feeding diets with high level protein. I would very much appreciate if you list those diets.

  • 02/14/2013 04:11am

    BenAv, we moved to Royal Canin Diabetic foods when they first came out as the highest protein content foods available. As it turned out, the cats just love this food, (even light eaters eat regularly), and we don't have them succumbing to nutrition related diseases at all. Those who have come to us with previously diagnosed disease do not deteriorate, either.

    The biggest problem we have is finding secondary foods that they will also enjoy in order to find alternate sources of nutrients and variety -- this concerns us a bit, but hasn't been an issue in over a decade.

    For some unexplainable reason this food also seems to reduce hairballs by a major proportion. We have little trouble except with one cat who insists on eating bigger servings than her tummy can hold, but this happens with all her food, and she is an isolated case.

  • TheOldBroad
    07/05/2012 02:20pm

    That is exactly the approach I take with these patients. As you well know, cats do not particularly like low protein diets and will often refuse to eat them. Not eating is worse than the benefits gained by low protein. I always stress the balance of quality of life over quantity of life.
    Dr. T

  • Sarcopenia
    07/05/2012 04:39pm

    One would think it would be common sense that if you don't supply the materials to ensure continuation of muscle strength, muscle strength won't be there. Only muscle meat will provide the right amino acids, and for cats that includes sulphur containing amino acids. As a secondary ingredient, I also don't mind corn gluten meal on the ingredient list as it does have all the appropriate proportions of amino acids -- including the sulphur containing ones.

    As for reduction of protein with age, I don't feed our pets less protein and so far none of them have developed nutrition related ailments while in our care. We feed what is appropriate to the species. For example, with cats, it should be common sense that feline appropriate ingredients are important, so that the cat can digest with little stress on organs such as kidneys. However, I firmly believe that this practice should start *early* in the pet's life as bad ingredients are likely what cause the bad kidneys to develop in the first place. Again, it should be common sense that the harder the digestive organs have to work, the quicker they are going to wear out, and break down. For me, that would result in looking for protein sources that are easier to digest rather than removing a percentage of protein from the daily diet.

    Thanks again, Dr Tudor, for a great article getting to the heart of the matter.

  • Geriatric Protein
    07/05/2012 07:45pm

    Thanks for this detailed explanation about higher protein for older pets, and for clearing up the confusion about higher protein and kidney health.

    I have heard a lot of different things from various dog owners about this, and I am very glad to see a professional and complete write-up about this topic.

    Very, very helpful ... as I do feed my senior dog a high-protein diet. It eases my mind greatly to know that this will not "cause" kidney disease. A lot of people do think that high-protein diets "cause" kidney problems.

    Thank you, Dr. Tudor.

  • Low Protein Diet
    07/08/2012 04:24am

    Thank you so much for this article...we found out in February that my 10.5 yo greyhound is in kidney failure. They recomended the low protein diet which she hates and was not eating. I decided that it would be worse to watch her starve, so decided to get some protein in her diet. Now I will return to a regular diet for her as she always seems hungry. I thought the low protein would slow down the disease, but according to you this is not so. I thank you for explaining this to me. I love my baby and want her time left here to be happy.

  • jeand50
    07/08/2012 05:10pm

    I am glad the article was helpful as you deal with your pet's kidney disease. Keep in mind that the symptoms of kidney failure also result in a pet's refusal to eat. You and your vet need to find that balance between enough protein to satisfy the taste buds and body but also maintain BUN levels as low as possible. This is an ever changing process for the course of the disease. Also adding phosphorus binders, antacids with aluminum hydroxide, also help control blood phosphorus levels and the ill effects that can have on body calcium equilibrium. Regular subcutaneous fluid therapy also dilutes the BUN in the blood and makes these patients feel better. By frequent monitoring of the BUN, Creatinine, phosphorus and electrolytes you can make adjustments in protein levels of the diet and modify phosphorus binding and fluid therapy. Since I blog about nutrition, the article focused only on protein and kidney failure. The treatment of kidney failure is about more than just protein as I hope this answer has shown. Yes I think kidney patients benefit from more protein, but they need this additional care. Simply returning to your regular food without other adjunct therapy could decrease the quality of life you seek for your baby's remaining time. I hope this has helped.
    Dr. T

  • Kidney Failure in Cats
    11/04/2012 11:32pm

    It seems that dealing with kidney disease in geriatric cats is a "darn if you do, darn if you don't" situation. No matter how the cat is fed - whether high protein or low protein - the cat loses in the end. If the cat is fed a low protein diet, then she is getting inadequate protein for muscle health. And if she is fed high protein, there is the ammonia/urea issue. I think that the fact that my cat is 14 1/2 perhaps I should just allow her to continue to eat her favorite foods. Isn't a shortened, happy life better than a long one with poor tasting food?

  • 11/05/2012 01:54am

    Yes, Samantha, that was what we decided, too, and our boy who was constantly showing borderline above and below CRF lived well into his 20's. He died of something other than kidney disease, basically because he was old and wearing out.

    No point in trying to feed what the pet doesn't want as that starts a very vicious cycle of eating disorders to battle and it isn't fun for you or your pet. All the research I did didn't convince me that trying to be "perfect" with dietary maintenance of CRF just wasn't worth the hassle for anyone.

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