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Only dogs whose kidney failure is advanced need very low-protein diets.
by CJ Puotinen
Every day, thousands of dogs are diagnosed with kidney disease. The first suggestion most conventional veterinarians make is to switch from whatever the dog has been eating to a low-protein “kidney diet” food. Clients are sent home with bags or cans of “prescription” food and warned not to feed high-protein foods or treats of any kind.
Most dogs, even chow hounds, approach their new, low-protein food with suspicion, since these diets are generally much less palatable than foods that contain more animal protein. Many refuse to eat. Conventional veterinarians are used to this response and tell their clients to stick to the new food for their dogs’ own good. “Your old food is too high in protein and will actually speed kidney failure,” they warn. “Keep giving him the prescription food. He’ll come around when he gets hungry enough.”
Eventually most CRF patients do accept their new food, though without much gusto or enthusiasm. Worse, despite their food’s low protein levels, the dogs’ slow deterioration continues.
Many look back, after their dogs have died, and wonder whether they did the right thing. Now a new approach to feeding dogs with kidney disease offers a different scenario – one that’s more likely to keep CRF dogs, and their human companions, happy.
A paradigm shift
It’s a fact of life that not all medical discoveries and “breakthroughs” in disease treatment prove to be as promising as they seemed at first. Adopted on the basis of a few small, encouraging studies, some strate-gies are found later to cause mixed or even adverse results.
This is definitely the case with the currently predominant treatment strategy of giving dogs with CRF a low-protein diet. Newer research has radically changed and fine-tuned the dietary recommendations for canine CRF patients. Those using the latest, recommendations to feed their CRF dogs a therapeutic home-prepared diet report excellent results. Best of all, most dogs love the combination of high-quality protein and freshly prepared ingredients.
Chronic renal failure affects male and female dogs of all breeds and all ages. Its underlying cause may be hereditary or related to inflammation, tick disease, progressive degeneration, damage following acute renal failure, or unknown causes. Acute renal failure may be triggered by a trauma injury, exposure to poisons like antifreeze or rat poison, or damage caused by medications, bacterial infections (such as leptospirosis), fungal infections, or dehydration.
Many animals born with poorly constructed or poorly functioning kidneys succumb to kidney failure at a young age. Most cases of chronic renal failure are seen in dogs age seven or older. Chronic nephritis, a common diagnosis in CRF patients, involves low-grade, long-term inflammation of kidney tissue that causes permanent damage to delicate renal tissue.
Conventional veterinary medicine considers all forms of kidney disease to be irreversible, progressive, and eventually fatal. But many holistic veterinarians disagree, saying that the progress of chronic renal failure can be interrupted or slowed with improved nutrition and holistic support.
“Since I turned to a natural approach to wellness,” says Florida veterinarian Russell Swift, DVM, “I have seen many dogs outlive their death sentence by years.”
Like many holistic vets, Dr. Swift blames a toxic lifestyle for causing many cases of CRF. “I believe the major reasons for kidney failure are poor-quality nutrition and exposure to toxins. Processed foods are a major contributor to kidney disease because they combine poor-quality ingredients with harmful additives or residues, and that leads to chronic illness. The inadequate and improper protein sources in processed foods and the low moisture content of dry foods are two major kidney stressors.
“When dogs are treated with prescription drugs for the problems that often accompany commercial diets, they are given nonsteroidal anti-inflammatories (NSAIDs), antibiotics, and other medications that are damaging to the kidneys. I also question the use of food additives and preservatives and the use of fluoride in drinking water, and don’t forget environmental toxins like lawn chemicals and other pesticides, including those that we use around ourselves and our companion animals. It’s a wonder more dogs don’t develop kidney problems.”
As soon as they diagnose kidney disease, most American veterinarians prescribe a low-protein diet. They believe that protein harms the kidneys and that reducing protein consumption slows the progress of kidney degeneration. This is because early research on rats was assumed to be true for dogs, and excess protein causes problems for rats. A number of pet food manufacturers sell low-protein prescription diets for dogs with chronic renal failure, and those who prepare their own food at home are warned against feeding meat, poultry, and other foods that are high in protein.
“Those recommendations are based on a myth,” says Wendy Volhard, author of Holistic Guide for a Healthy Dog. “In fact, the whole theory of low-protein diets for dogs with kidney disease was blown apart in 1975 by David Kronfeld, PhD, who was at the time a veterinary researcher at the University of Pennsylvania. His concept was not to feed less protein but rather to feed higher-quality protein.
“The low-protein myth is like an old-wive’s tale, something based on ignorance that just won’t die. Yes, inferior-quality protein can harm a dog’s kidneys, but the solution isn’t to continue with inferior-quality ingredients and feed less of them. The solution is to improve the quality of ingredients and in that way provide what the dog needs for good health.”
Studies disproving the prevalent low-protein prescription have been widely published in veterinary journals and textbooks. But it is moving into the mainstream very slowly.
“Most vets who did not graduate from college in the last few years (and some of those as well) are still unaware of or dismiss the newer studies that show low-protein diets neither slow the progression of kidney disease nor prolong life,” says Mary Straus, a lifetime dog lover from the San Francisco Bay area who researches health and nutrition issues.
“Too many dogs are forced to eat Prescription Diet k/d® or similar low-protein prescription foods,” says Straus. “These can actually cause harm. When protein levels are very low, the body will cannibalize itself to get the protein it needs. This creates more waste products than if you feed the proper amount of high-quality protein in the first place. Also, k/d is not very palatable, and many dogs with kidney disease will eat only enough of it to survive, or stop eating entirely if that is all they are offered.”
Older dogs actually require a higher level of protein to maintain their body stores of protein than do younger adult dogs, says veterinary nutritionist Patricia Schenck, DVM, PhD, of Michigan State University’s Center for Veterinary Medicine. In an article published in Veterinary Nutritionist, Dr. Schenck wrote, “Reducing dietary protein in older pets may have adverse effects. As pets age, their ability to utilize nutrients decreases. The only time dietary protein restriction is appropriate in renal failure is when the disease has become severe.”
Healthy geriatric dogs require about 50 percent more protein than young adults, say canine health writers Susan Thorpe-Vargas, PhD, and John C. Cargill, MA. Depending on the quality of the protein, they say, it should make up 20 to 30 percent of total calories ingested. “Protein restriction can result in impaired wound healing, diminished immune function, and lowered enzyme activities and cellular turnover. Dogs with impaired renal function do better with dietary phosphorus restrictions.”
Mary Straus’s dog Nattie was a healthy, athletic Chinese Shar-Pei who had no trouble keeping up with young dogs even at 10 and 11 years of age. She ate kibble and received annual vaccinations until 1997, when Straus learned about the health benefits of raw diets and the harm that can be caused by repeated vaccinations. Nattie was 10 years old when she was converted to a raw diet and stopped receiving vaccinations. Four years later, at age 14, Nattie was diagnosed with kidney disease. After much research, Straus put the newest diet plan into place for Nattie.
“I modified her diet to reduce its phosphorus but kept her protein levels high,” says Straus. “Her diet was around 37 percent protein on a dry matter basis, and she thrived. Her kidney numbers actually improved for two years, and when she died at age 16, her illness had nothing to do with kidney disease.
“People need to know this information, as well as how to formulate a homemade diet or what foods to add if they are going to feed k/d or one of the other low-protein commercial diets for kidney disease.”
When developing a diet for dogs with kidney failure, the recommendations from leading experts are to feed
• moderate to high amounts of fat,
• moderate amounts of high-quality protein,
• low amounts of phosphorus,
• moderate amounts of low-phosphorus carbohydrates,
• and plenty of water, juices, broth, and other liquids.
Although guidelines vary, a sensible goal is a diet whose total calories come 1/3 from fat, 1/3 from protein, and 1/3 from carbohydrates.
Fat provides calories and energy, and most dogs have an easy time digesting it. Good sources of saturated fat include fatty meats, butter, whole-milk yogurt, egg yolks, and coconut oil.
Polyunsaturated vegetable oils, such as canola, corn, soy, safflower, sunflower, and flax seed oil, are not recommended for CRF patients. Neither is cod liver oil, because of its high vitamin D content, which failing kidneys have difficulty processing. But fish oil (fish body oil, not fish liver oil) has been shown to help dogs with CRF.
When adding fats and oils to the home-prepared diet, start with small amounts and increase quantities gradually. Too much too soon can lead to diarrhea. Dogs prone to pancreatitis should be carefully monitored.
What are the best sources of protein? Most experts consider eggs to contain the highest-quality protein, but their yolks contain moderate amounts of phosphorous. One strategy for feeding eggs to CRF dogs is to feed one or two egg whites for every whole egg. Calcium is a phosphorus binder, so add small amounts of finely ground eggshell to each meal (½ teaspoon per pound of food) to help reduce the amount of phosphorus absorbed by the body.
Other foods high in phosphorous include bones, fish with bones, cheese, and organ meats. “Bones are so high in phosphorus,” says Straus. “that I would avoid them or feed them in small amounts, such as one-third the normal quantity, even with early stage CRF. Like egg yolks, organ meats such as kidney and liver contain many nutrients that are important for canine health and should be included, but in moderate amounts.”
Further diet tips
Recently, green tripe, a food traditionally fed in Europe, has become a staple for many American dogs, including CRF patients. Green tripe is the raw, unprocessed stomachs of cud-chewing animals like cows, goats, or sheep. Supermarket tripe is white because it has been bleached and deodorized, which destroys fragile nutrients. Green tripe contains easily digestible protein, beneficial bacteria, abundant enzymes, and relatively low phosphorus levels.
Tripe smells awful to humans but sublime to dogs, including CRF patients who have otherwise lost interest in food. Thanks to increasing demand, frozen green tripe is available from mail order sources and some local distributors of raw frozen foods.
If you choose to feed a prescription dry or canned food rather than a home-prepared diet, add fresh protein foods, either raw or cooked, such as meat, eggs, egg whites, and tripe, especially in the early stages of the disease.
If you feed a diet based on raw meaty bones, substantially reduce the amount of bone. If the diet calls for bone meal, like the Natural Diet developed by Wendy Volhard, follow her advice to switch from lean to fatty meats and substitute calcium carbonate for the bone meal to reduce phosphorus levels.
While dogs are not designed to consume grains or starchy vegetables, most CRF diets include up to 50 percent carbohydrates in order to provide calories and nutrients while keeping phosphorus levels low. Steaming or boiling vegetables reduces phosphorus levels if you discard the cooking water. Alternatively, puree or juice them to improve assimilation. Note, however, that dogs with arthritis may be sensitive to nightshade plants, which include white potatoes, peppers, eggplant, and tomatoes.
Whole wheat, oatmeal, brown rice, millet, and other whole grains are moderately high in phosphorus and should not be fed often or in large amounts. White rice is low in phosphorus, and glutinous or sticky rice is the lowest-phosphorus grain. To help make grains more digestible (as described in “It’s All in How You Make It,” WDJ March 2001), soak them overnight to remove enzyme-suppressors and naturally occurring toxins.
“I have had good luck with Malt-o-Meal, which is low in phosphorus,” says Straus. “You have to be careful about feeding vegetables to dogs with kidney disease. I recommend using white potatoes and yams because they provide a lot of calories without adding much phosphorus, unlike many of the low-cal veggies.”
Dogs with high blood pressure, which can be related to kidney disease, may need reduced salt in their food. Home-prepared diets are naturally low in salt, but cottage cheese is high in salt, canned fish can be rinsed to remove salt, and processed foods should be checked for their sodium content.
Because dehydration creates serious problems for dogs with kidney disease, it’s important to provide abundant water. “Make sure fresh water is always available,” suggests Straus, “even if excess drinking causes your dog to become incontinent. If your dog already drinks a lot of water, ask your vet about giving subcutaneous fluids to help the dog stay hydrated.” Hard water contains minerals that are best avoided, so use filtered or low-mineral bottled water.
Dogs with kidney disease can lose interest in food, so look for foods and flavors that can revitalize a flagging appetite. “It’s important for these dogs to eat something,” says Straus, “even if it’s not one of the recommended foods. Try offering your dog’s food at different temperatures, experiment with raw versus cooked, and offer multiple small meals rather than just one or two large ones. My Nattie wouldn’t eat raw eggs, but she loved eggs scrambled with a bit of cheese. The cheese wasn’t the best thing for her, but it got her to eat.”
Green tripe can be added to food as a flavor enhancer, as can Seacure, a very fishy-smelling powder sold as a protein supplement. “If you feed a commercial food like k/d and your dog won’t eat it, find something else, preferably a homemade diet that provides high-quality protein while controlling the amount of phosphorus,” she says.
Plus, she adds, most dogs love fresh food
Hill’s differs with our opinion on diets for dogs with chronic renal failure; we respectfully disagree with Hill’s.
Dear readers: In May 2005, we published an article by longtime WDJ writer and book author CJ Puotinen about dietary considerations for dogs with renal failure. Quoted several times in “When to Say No to Low-Protein,” was dog owner Mary Straus, a researcher who has exhaustively studied the veterinary literature regarding treatments for chronic renal failure (CRF).
In response to our article, we received a long letter from S. Dru Forrester, DVM, MS, Diplomate ACVIM (Small Animal Internal Medicine), a scientific spokesman for Hill’s Pet Nutrition. Dr. Forrester began his letter with a statement that our article contained inaccurate information, and that some of the recommendations in the article could cause “significant harm” to dogs suffering from chronic kidney disease.
However, after going through Dr. Forrester’s letter with a fine-tooth comb, we feel confident that our article contained no errors, but rather, statements that represent different opinions from those of Dr. Forrester and Hill’s.
We shared Dr. Forrester’s letter with Mary Straus, as, quite frankly, we needed some help finding and checking the 10 footnoted studies Dr. Forrester referred to in support of his critique of our article. Straus not only had the studies on hand, but also was familiar with them. Shortly after she received Dr. Forrester’s letter, Straus countered with an even longer letter, citing 30 footnoted references in support of her critique of Dr. Forrester’s letter.
There is some pretty fascinating stuff in these letters – fascinating, at least, to us dog food geeks! In recognition of the fact that not all of our readers may be similarly enthralled, we offer below an edited version of the two letters. Interested individuals can contact us if they are interested in receiving the complete text of both letters.
Hill’s pioneered the field of clinical veterinary nutrition, and has always been the leader of that new industry. Its founder, a brilliant and visionary veterinarian, Mark L. Morris, Sr., may have been the first modern veterinarian to recognize the therapeutic value of adjusting the diet of animals as part of a veterinary response to their disease; the company was founded on a product he developed in 1939 to treat dogs with kidney failure – a product that is still a company best-seller.
We respect Hill’s history and acknowledge its enormous contributions to the field, but also wish to note that its oldest product (Prescription Diet® Canine k/d®) has changed over the years in response to new developments – meaning it might change again, perhaps even to incorporate some of the research we cited in our article. Other companies now make foods for dogs with kidney failure, and the resulting products are not all alike.
“When to Say No to Low-Protein” expressed our support for some different ideas. We don’t believe that Hill’s currently possesses the only correct prescription for feeding a dog with renal failure, nor the best one.
–Nancy Kerns, Editor
I discovered several inaccuracies when reading “When to Say No to Low-Protein.” The article summarizes dietary treatment for chronic renal failure (CRF), now known as chronic kidney disease (CKD), in dogs. The author recommends a new approach to feeding dogs with kidney disease and states that newer research has radically changed and fine-tuned dietary recommendations for canine CKD patients.
Some of the recommendations in the article are appropriate; however, others could cause significant harm to dogs suffering from CKD. The readers of your journal should be aware of this information when making decisions about what to feed their dogs with CKD.
The author is correct that newer research has radically changed and fine-tuned the dietary recommendations for canine CKD patients; however, current recommendations made by veterinary nephrologists contradict those made by the author of this article.
The most current findings available are from a clinical study of dogs with naturally occurring CKD conducted at the University of Minnesota by leading experts in the field of veterinary nephrology... These findings further support current recommendations made by veterinary nephrologists to feed a therapeutic food such as Prescription Diet® Canine k/d® to dogs with CKD. Therapeutic foods such as Prescription Diet® Canine k/d® are indicated before kidney disease becomes severe; they should be fed when serum creatinine concentration is greater than or equal to 2 mg/dl. Waiting until kidney failure is more advanced decreases patient survival time and quality of life and also may decrease acceptability of the therapeutic food.
When calculating dietary protein requirements, one must consider digestibility and quality of the protein source. Digestibility refers to the amount of protein available for absorption and subsequent use by the pet. High quality protein sources deliver essential amino acids, those that cannot be synthesized by the pet.
As the quality and digestibility of the protein source increases, the amount of protein required in pet food decreases. Prescription Diet® Canine k/d® contains proteins that are of high quality and digestibility, therefore, a lesser amount of protein can be used to meet maintenance requirements for dogs.
The role of dietary protein restriction in dogs continues to be debated amongst veterinary nephrologists. To date, studies have not shown a conclusive effect on delaying progression of experimentally induced CKD in dogs; however, there have been beneficial effects observed in dogs with naturally occurring kidney diseases.
It is generally accepted that reducing protein intake decreases blood urea nitrogen (BUN) concentrations and ameliorates clinical signs of uremia in patients with CKD. In addition, restricting dietary protein may help ameliorate effects of metabolic acidosis, common in CKD.
Although further evaluation is needed, dietary protein restriction is associated with reduced magnitude of urine protein loss (i.e., proteinuria) in dogs with glomerular diseases (i.e., kidney diseases characterized by increased permeability of glomerular blood vessels that allow protein leakage into the urine).
Protein supplementation (e.g., meat, eggs, tripe) is contraindicated in these patients because it may worsen severity of proteinuria and subsequent hypoalbuminemia (decreased protein concentration in the blood).
The reader should also be aware that feeding a food with reduced protein is only part of the picture when talking about therapeutic foods such as Prescription Diet® Canine k/d®. Other beneficial components of these foods include moderate phosphate restriction, moderate sodium restriction, increased supplementation with polyunsaturated fatty acids (PUFA), increased B vitamins, and increased buffering capacity (to counteract the tendency toward decreased acid excretion by the kidneys).
In the past, owners of dogs with CKD often found that therapeutic kidney foods were not very palatable. Prescription Diet® Canine k/d® dry and wet formulas have undergone several improvements in palatability during the past several years and most dogs with CKD readily accept these foods.
It is important to slowly transition a dog from the old food to the new therapeutic food over a seven-day period. Dogs with advanced CKD often are nauseated and will not be interested in any type of food. Clinical signs of nausea and vomiting should be controlled before attempting to introduce a new food.
There are no nutritional reasons that support providing excessive amounts of dietary protein; older dogs (> 7 years) do not require more protein than young adults. In fact, subclinical kidney disease may exist in apparently healthy older or geriatric dogs and kidney function can be worsened by feeding excessive protein (and phosphorus) to these patients.
In summary, your readers should be aware that kidney therapeutic foods are routinely recommended by veterinary nephrologists and small animal internists for managing dogs with CKD. Prescription Diet® Canine k/d® contains reduced amounts of high quality, highly digestible protein that is more than adequate for maintenance needs of adult dogs. To date, Prescription Diet® Canine k/d® is the only kidney therapeutic food that has been studied in dogs with naturally occurring CKD. Feeding Prescription Diet® Canine k/d® to dogs with CKD prolongs survival time and improves quality of life for these patients.
S. Dru Forrester, DVM MS
Scientific Spokesman, Hill’s Pet Nutrition
I would like to respond to the allegations in the letter above regarding supposed inaccuracies in the WDJ article, “When to Say No to Low-Protein” – allegations I believe are wholly without foundation.
Dr. Forrester’s letter says that “current recommendations made by veterinary nephrologists contradict those made by the author of this article,” then goes on to give the results of a study that compared the use of Prescription Diet® Canine k/d® (here-after referred to as k/d) with maintenance kibble.
I do not believe that dogs with CKD should be fed maintenance kibble, nor does WDJ advocate this. The article clearly stated that dogs with CKD need a reduced phosphorus diet, and advocated feeding a home-prepared diet that reduces phosphorus without overly restricting protein.
I agree that diet should be modified before kidney disease becomes severe, and the WDJ article specifically suggests reducing phosphorus “even with early stage CRF.”
I do not agree that protein should be restricted at this stage, or that the level of phosphorus restriction in k/d is required for early stage renal disease. According to the Nutrition Support Service at Ohio State University Veterinary Hospital, “Results of recent research are changing our recommendations for nutrient modification in dogs with early signs of CRF. Restricting phosphorus intake to about 30 mg/pound/day [about half the amount found in normal diets] as soon as polyuria is recognized, and supplementing potassium intake (with alkalinizing salts if acidosis is a concern) to maintain serum potassium within the normal range may be all that is necessary until patients develop severe disease.”
There have been no studies done that I’m aware of showing that lower amounts of high quality protein do not cause problems due to protein deficiency in dogs with CKD. Suggestions I saw regarding the use of high quality proteins for dogs with kidney disease specifically suggested not reducing the quantity of protein below levels referenced above, but instead increasing the quality of protein fed.
I would also dispute Hill’s claim that it contains “proteins that are of high quality and digestibility.” The ingredients in Canine k/d are “brewers rice, pork fat (preserved with mixed tocopherols and citric acid), dried egg product, flaxseed, corn gluten meal, chicken liver flavor, soy fiber,” plus supplements and artificial preservatives. Of these, only eggs would be considered high quality protein (and “dried egg product” is almost certain lower quality than fresh eggs). Corn gluten meal and brewers rice are poor quality and incomplete proteins. None of the other ingredients provide protein at all.
It is true that reducing protein decreases BUN, but this is only significant when BUN is high enough to cause signs of uremia (in general, over 80 mg/dl). Our article did advise reducing protein when a dog is uremic. But no studies have shown that reducing protein improves quality of life, extends life, or slows the progression of kidney disease when instituted before a dog is uremic.
The studies cited by Hill’s that purportedly show otherwise apply only to dogs with canine X-linked hereditary nephritis (a rare, breed-specific form of juvenile renal disease), and the first study only indicates that a protein restricted diet reduces proteinuria, which is a symptom (comparable to BUN) that is related to the amount of protein in the diet and does not mean that there is any actual benefit from the reduction. The first study also indicates that the dogs fed the low protein diet “did not maintain starting body weight or plasma albumin concentration within the normal reference range,” dangerous side effects of low protein diets, and that “unintended differences in digestibility of protein and energy prevented assignment of the diet effect exclusively to protein.” I would argue that this study actually supports WDJ’s contention that low protein diets can be harmful.
Concerning metabolic acidosis: I looked up the references cited in Dr. Forrester’s letter. The first one cited is the study noted above, which indicates that low protein diets led to loss of body weight and hypoalbuminemia. Proteinuria may lead to hypoalbuminemia as well, but not because there is too much protein in the diet, but rather because protein is being lost faster than it is being restored.
Proteinuria is a symptom, not a cause, of renal disease. In reality, higher protein diets may be required when dealing with proteinuria and hypoalbuminemia, due to the excessive loss of protein through the kidneys.
Dr. Forrester points our that feeding a food with reduced protein is only part of the picture when feeding dogs with CKD. The WDJ article recommended phosphorus restriction and supplementation with B vitamins. Supplementation with omega-3 fatty acids was also highly recommended.
Hill’s admits that their diets have not been palatable in the past, but claims they are improved now. I would suggest that they would have made the same claims in the past, and will at some point in the future likely make further changes that they will then claim make their food more palatable than it is now.
The fact is that low protein foods are inherently less palatable, and that commercial diets will never appeal as much to a dog as fresh food diets. Anecdotally, many people still report their dogs refusing to eat Prescription Diet® Canine k/d®. Even if some dogs are willing to eat this food, it is not unreasonable to suggest alternatives for those that will not, or additives that will make it more appealing, as well as healthier, for dogs with early to moderate stage CKD.
There are many recent studies that indicate older dogs, even those with kidney disease, may need more protein than younger dogs. As to older dogs that “may” have subclinical kidney disease, low protein diets have not been shown to benefit dogs that do have kidney disease, nor have they been shown to reduce the risk of kidney disease or slow its progression. There are no studies indicating that feeding excessive protein to older dogs is harmful. In contrast, research over the past 10 years or so has shown that protein does not harm the kidney of dogs.
In summary, I stand by the recommendations in the WDJ article. I will continue to recommend that dogs with kidney problems receive adequate amounts of protein, along with fish oil (not the flaxseed found in Canine k/d®) and high quality fresh foods that they enjoy, and that moderate, rather than severe, restriction of phosphorus is all that is needed for early stage renal disease. I also stand by the assertion that older dogs, including those with CKD, do not benefit, and may be harmed, by excessive protein restriction.
Mary Straus , Pleasanton, CA
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