You know why your dog or cat has kidney disease, mainly because of dry dog food. If your vet recommends a low-protein dog food to benefit his failing kidneys, you should strongly question this advice. If you’ve heard enough, jump to Kidney Disease in Dogs Part 4: The Solution.
This series on kidney disease in dogs has been split into four separate articles:
- Article 1: An overview of kidney disease in dogs
- Article 2: Why dry food causes kidney disease
- Article 3: Why low protein dry food goes directly against the available science on kidney disease in dogs (this article)
- Article 4: The best diet for dogs with kidney disease
In this article, I’ll cover:
Why is my vet recommending a low-protein dog food?
Vets are used to examining the blood results of animals fed minimum protein diets.
Conventionally trained vets learn that the liver and kidneys may no longer function when protein rises in the blood. Protein is a valuable bioindicator of what might be happening under the hood. All makes perfect sense; nothing wrong so far.
More and more people are starting to feed their dogs like the little meat-eaters they most certainly are, to the great benefit of their health. This means a diet of lots of protein and a little fat (for example, a rabbit, should you suck all the water out of him, is perhaps 70-80% protein and 10% fat. While many pre-made raw dog foods produce excellent products to this protein: fat ratio, many of the cheaper brands (and indeed our mixes we make ourselves) are usually a little fattier.
Compare this natural diet to cereal-based dog food. These animals exist on a diet of 18-22% protein, the minimum you can use in pet food, and state it is “complete by AAFCO standards.” The rest of these products are cereal, with around 50-60% carbohydrate.
These are two very different feeding styles, one getting lots of protein and the other the minimum required. It should thus come as no surprise that when their blood is tested, raw-fed dogs have significantly more protein in their blood, around 20-30% more.
This high blood protein rings alarm bells for your conventionally trained vet who has been using for their comparison laboratory dogs fed standard, cereal-based diets, food that is desperately low in protein. Of course, dogs fed a slightly more luxurious diet containing more meat always risk appearing to have “excessive levels of protein in their blood,” but this is not because they are sick; it’s just because they’ve been eating more.
The theory from dry food manufacturers and the vets they educate is that this extra blood nitrogen risks creating an additional load on the kidneys, as they need to filter all this “excess protein” from the blood. So your vet then reaches for the low-protein dry food to try and control this rise. It makes sense, doesn’t it?!
Is there a time when dogs with kidney disease may need low protein?
The theory above has a tiny bit of weight in that one or two instances in treating human kidney disease where low protein is recommended. These are just before beginning dialysis (after which they are advised to increase their fresh protein intake to normal levels afterward, something dogs can’t do anyway) or if you have proteinuria (very dangerously high blood urea nitrogen, which in dogs is a BUN level of 80. This is rare and an indication that the dog is in the very end stage of kidney failure and severe trouble. So, yes, low protein at this time is sound advice).
But what of every dog in between this?!
Studies show that even with their kidney function reduced by 90%, dogs do better on higher protein diets.
Somewhat unsurprisingly, as meat eaters, studies show dogs thrive on high protein diets (Robertson et al. 1986, Bovée 1991, Finco et al. 1994, Hansen et al. 1992, Laflamme et al. 2008). Moreover, their ability to process the protein is so efficient that before feeding them the high-dose protein diets, many of the studies authors cited above actually removed 75% (and as much as 90%) of the kidney function in healthy dogs (by chopping off the supply to the rest of the organ), to replicate chronic kidney failure. All these studies unequivocally prove that dogs with CKF can safely deal with and do better on higher protein diets than on low protein dog food.
“…renal function and biochemical responses to dietary changes were studied in four dogs with stable chronic renal failure. The objective was to determine if dogs with moderate stable failure adjust to diets with varied protein and electrolyte content. These dogs were found to have the capacity to adapt to a wide range of dietary protein and electrolyte intake. The only exception was found in dogs fed a reduced-protein diet, which failed to appropriately adjust renal tubular excretion of sodium and phosphate. The only advantage of reduced dietary protein in this study was a reduction in blood urea nitrogen (BUN). The disadvantages of reduced-protein diets were reduced glomerular filtration rate (GFR) and renal plasma flow.”Bovée 1991
I can find just one study that seems to disagree with the above. Upon seeing 10 cats suffering from kidney disease on a higher protein (40%), commercial dry diet, DiBartola et al. (1993) replicated the diet in 9 laboratory cats. They note that phosphoric acid was added during production, as in the first diet. Three of the nine previously normal cats suffered renal dysfunction and renal lesions in just two years. However, we cannot say for sure what the problem is here. Maybe it was the presence of phosphoric acid added to the mix. We know that it is the inorganic forms of phosphorus used in dry foods (monosodium and dicalcium phosphate) that affect postprandial plasma phosphorus in cats (Alexander et al. 2018, Coltherd et al. 2019), NOT phosphorus occurring naturally in food items such as meat or vegetables seems to have little to no effect whatsoever (this is crucial for your diet advice going forward, we will revisit this in Part 3).
As always, the science supporting dry food is dangerously out of whack.
Dry food companies illuminate the front of their food bags “clinically proven to benefit kidney disease in dogs.” But unfortunately, there is no mention of the study on the bag. Were they talking about dogs in proteinuria whereby a lower protein diet might have helped? Or are they reducing the salt content of their kidney food which would instantly make the kidneys happy? Or is the food more digestible? Or less antigenic somehow? Maybe it’s wheat free; that’d be nice. Or perhaps the manufacturer who conducted the trial in-house put the decimal point in the wrong place, and the food didn’t help. What we’re missing is actual evidence. It’s worrying our vets are not asking for this.
The fact remains that vets and dry food companies are the only people calling for low protein diets as a starting point to treat kidney disease in dogs (and senior dogs, God don’t get me started there). Now it happens that protein is expensive compared to carbohydrates. This is why most dry dog foods include so much cereal. By incriminating protein, they can consist of even more cheap carbohydrate filler. Crystals aside, all these carbs convert to sugar in the blood, which is balanced by lots of insulin. Excess insulin and soon insulin resistance contribute to the metabolic syndrome that is associated with the development of kidney disease too.
It’s all so wrong.
What protein is best for dogs with kidney disease?
Fresh, fresh, fresh REAL, high quality (organic is best!) protein in the form of meat! I think it has been made as clear as possible. Dry food is not recommended here, so let’s look at what you should feed and what is best for a dog with kidney disease.
- Take me to part 4: What to Feed to Dogs With Kidney Disease
- Take me back to part 2: Dry Food Fueling Kidney Disease in Dogs
- Take me back to 1: Kidney Disease in Dogs
References Used but Not Linked
ANTECH Diagnostics (2003). ANTECH News, online journal, June 2003
Finco, D. R., Brown, S. A., Crowell, W. A., Brown, C. A., Barsanti, J. A., Carey, D. P., et al. (1994). Effects of aging and dietary protein intake on uninephrectomized geriatric dogs. American Journal of Veterinary Research, 55: 1282–1290