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Proteins, Kidneys, Senior Dogs

Proteins, Kidneys and Senior Dogs

By Lew Olson • April 2003 Newsletter
There seems to be a lot of confusion on the topic of protein amounts for dogs and the effects it has on kidney function. Several years ago, the common rule of thumb was to reduce the amount of protein in senior dogs and dogs with any symptoms of kidney problems.

These ideas are now considered myths, as protein is very important to the dog’s health.

Proteins consist of chains of amino acids which have several important needs in the dog.
– They maintain the structure of skin, hair, tendons, ligaments, cartilage and nails.
– Protein is needed for the production of new tissue
– Protein maintains normal metabolic processes in the body.
– It is the necessary nutrient for repair of tissues, and this includes the major organs in the body.
If enough protein isn’t present in the diet, dogs will lose lean body mass, loss weight, become lethargic, and develop a lowered immune system. Young animals will show impaired growth and development. It has also been shown that minimum protein amounts can cause dogs to be more sensitive to the toxic effects of certain drugs.
Allison JB, Wannemacher RW, Migilarese JF: Diet and the Metabolism of 2-Aminoflorene, Journal of Nutrition 52:415-425, 1954.
While in the past it was believed that excess protein might cause problems in dogs, it has been shown that dogs have the ability to metabolize excess protein. Protein is an essential part of the canine’s diet, and is necessary to sustain life and maintain the integrity of the internal organs.
More recent studies show today that it is probably more harmful than it is good to restrict protein in senior dogs, and the high quality proteins are needed for our older pets.
These would include animal proteins that haven’t suffered high degradation (high heats, over processing). The dog’s body must be able to utilize the protein. Poor protein sources for dogs include waste animal proteins (unfit for human consumption), over processed proteins and plant proteins (plant proteins are incomplete in the amino acids needed for canine health). If a processed dog food is given, always check the ingredients and know the source of the proteins listed.
Earl Wolfe’s web site on dog food comparison and information on ingredients is a great place to start for this: home.hawaii.rr.com/wolfepack/food.html
For information on the highest digestible foods (pre-made raw) go here: www.dogaware.com/dogfeeding.html#frozenraw. This site also offers more links on commercial diets as well as cooked diets.
OK, so back to the question most people ask: When is the right time to reduce protein? According to the research presented by Mary Straus (who graciously agreed to let me borrow at will from her fabulous website on this topic):
“It is my understanding, based on research done in the last ten years, that the only time it is necessary to feed a low protein diet is when your dog is uremic, which generally means BUN is over 80 mg/dL (equivalent to approx. 28.6 mmol/L), creatinine is over 2.5 mg/dL, and the dog is showing symptoms such as vomiting, nausea, inappetance, ulcers and lethargy, which are caused by the build-up of nitrogen in the blood. Even then, feeding low protein will not extend life, but it will help the dog feel better. Subcutaneous fluids can also help at this time. www.dogaware.com/kidney.html
“BLOOD UREA NITROGEN (BUN) – This is a protein metabolyte excreted by the kidney (it is one of the toxins we are concerned about). In a normal animal, the BUN is 25 or so. A good goal for BUN in kidney failure is 60-80. Often at the time of diagnosis, BUN is well over 150, 200, or even 300.”
“CREATININE – This is another protein metabolyte (though this one is less dependent on dietary protein intake than is BUN). A normal creatinine is less than 2.0. A good goal in kidney failure is a creatinine of 4.5 or less. BUN and creatinine will be tracked (as will several other parameters) over time and in response to different treatments.”
Here is a site for further information on various tests to evaluate kidney function: www.marvistavet.com/html/body_chronic_renal_failure.html#RelaventDiagnosticTests
If both urinalysis and blood paneling testing shows kidney damage or early failure, only if the high BUN and creatinine levels are at or exceed the numbers listed above, should a lower protein diet be considered. And this would not necessarily extend life, but would alleviate the symptoms caused by nitrogen build up (created by protein intake that taxes kidneys in chronic renal failure). It is at this point that the caretaker of the dog would need to make some decisions, based on the dog. Does the dog enjoy the reduced protein meal? Is the dog showing the symptoms of nausea, inappetance, ulcer and lethargy? Is the diet helping to stop these symptoms? And is the dog past the growing stages, where a reduced protein diet would not affect the dog’s growth stages and nutritional health?
Also please remember, changes in the amount of protein given in the diet are unneccessary until the dog’s blood panels reach the levels of BUN and creatinine listed above. Reducing protein before this time has been shown to actually do more harm than good. Removing the building blocks of maintaining good organ integrity can actually starve the body of what it needs for continued good health.
Other diet changes may help if there are other associated problems. If the dog has high blood pressure, reducing sodium in the diet is important. If the dog has elevated potassium levels, then reduced potassium is necessary. Additionally, reducing phosphorus intake is important with kidney disease (see more below), but reducing protein is unnecessary.

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The newest research shows it isn’t the protein that causes damage to the kidneys as much as it is the phosphorus contained in the protein.

“Is it possible that the influence of phosphorus in the very earliest stages of kidney failure has been over-looked? Have we clinicians been in error by waiting until terminal kidney failure to aggressively manage phosphorus? Several teams of researchers think so, and indeed, at least one study has taken several groups of dogs in kidney failure and fed them diets that varied in protein level and phosphorus level. The groups with severely restricted phosphorus lived longer than the groups with normal or high levels of phosphorus. The protein intake made no difference at all in longevity. This is important information, because owners are often told that high protein diets can cause premature aging of kidneys and renal failure, even in the normal dog; no experimental proof of this exists. Experiments on the longevity of renal failure patients fed different phosphorus levels is being repeated by different researchers using different models of kidney damage (surgical resection, bacterial infection, blood flow occlusion), but some clinical veterinary scientists are already looking at kidney disease from a phoshorus (rather than a protein) perspective.” www.geocities.com/willowind_dals/gearhart2.html
This article goes on to state that using a new therapy, Calcitriol, a vitamin D therapy may be beneficial and proponents believe it can actually extend life expectancy. When kidneys are compromised, they are unable to absorb calcium effectively. This creates leaching of calcium from the bones, and too much phosphorus in the system. It is thought calcitriol helps to absorb the calcium better, which helps to balance the phosphorus in the system. When calcitriol is given, medical monitoring by a veterinarian is pertinent to insure the proper amounts are being given.
For further information on determining phosphorus in various foods, information on phosphorus binders and other medications, plus comparing commercial kidney diets and information on homemade diets, go to Mary Straus’s wonderful page www.dogaware.com/
It is not hard to make a homemade diet at home, and it is comforting to be able to control the ingredients, quality and adjust the recipe as needed.
Lastly, there are some supplements that can help with supporting the kidneys.
Salmon Oil or Fish Body Oil
These oils are high in omega 3 fatty acids, which have proven benefits for being renal protective.
“In two studies, one from 2000 and the other from 1998, dogs with induced kidney disease showed improvement when they were fed omega-3-rich fish oil supplements, compared to omega-6-rich safflower oil supplements.
Vitamin E
Shows benefits of protecting the kidney by stopping oxidation damage. www.purina.com/images/articles/pdf/OxidantsAndAntioxidantsIn.pdf
Vitamin C and B Complex
“We also recommend B-complex and vitamin C to help the well being of your dog and also replenish the vitamins lost due to the inability of the kidneys to recycle and retain the nutrients in the body properly. www.cah.com/library/caninekidney.html
In summary, it is apparent that new research and information has proven that protein does not harm senior dogs, will not cause kidney damage, and that highly digestible proteins can actually benefit a dog with renal problems. It is important to understand what blood and urinalysis values mean to determine renal affects and for decision making to determine if diet changes are necessary, and what direction to proceed. Equally important is to understand what restricting protein can mean to a growing puppy or young dog. I hope the references I have provided you here will help with these decisions.
Always get a full chemistry workup and a veterinary diagnosis to make the best treatment decisions for each individual dog.
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