Why Kidney Diets Don't Work (Part 2)

by Sarah Griffiths, DCH in Dogs, Cats
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By Sarah Griffiths, DCH & Inna Shekhtmann

April 27, 2018

In our last blog, we discussed how feeding a dry food diet to your pet can affect kidney health and what you can do to prevent kidney disease. If you missed it, click here to read. This week, let’s talk about the disease and what you can do when you get the diagnosis.   

Kidney disease doesn’t show up overnight. Chronic renal failure (CRF) takes years to develop in your pet through ongoing stress on the kidneys. It’s important to get regular blood testing and veterinary checkups done in order to catch it as early as possible. This can help to slow down the disease and damage to the kidneys. So can the right diet.

Unfortunately, what often happens when your pet’s bloodwork comes back with indicators of kidney disease is that they get put on a “kidney diet.” This is a one-size-fits-all hammer approach to a complex and diverse metabolic disease. It is designed to manage the disease – not solve the underlying cause.

Let’s take an in-depth look at this diagnosis, how it’s treated, and what you can do to help your pet get better.

Is it Really Kidney Disease? 

Kidney disease is a broad term used to indicate that the kidneys are under stress either due to an acute cause or chronic (degenerative) kidney disease. Kidney disease shows up as number of physical symptoms as well as indicators in bloodwork.  Here are two key things to consider in the diagnosis process:

  1. An accurate diagnosis should include both clinical symptoms and laboratory findings.  Animals are sometimes misdiagnosed with kidney disease based solely on laboratory findings rather than assessing the clinical symptoms in relation to the blood results. This is especially common with raw-fed dogs and cats, as discussed later in this article. 
  1. For acute kidney disease, it is important to try and identify the cause (poisoning, infection, injury, reaction to a drug) to determine the best course of treatment. If the underlying cause is discovered, the cause can be managed and damage to the kidneys can be slowed or halted, in some cases. In contrast, ignoring the underlying cause and managing the disease with a “kidney diet” can lead to the chronic form of the disease which is irreversible. 

 

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Symptoms and Laboratory Findings for Kidney Disease

Clinical symptoms: Clinical symptoms are the physical manifestations of disease that can be observed in the patient. With kidney disease, clinical symptoms include: lethargy, increased thirst, increased drinking, dilute urine, weight loss, nausea, vomiting, decreased appetite, dull hair coat and more. 

Laboratory findings: Bloodwork and urinalysis are the two most commonly used tests that help to determine kidney function. Your veterinarian will look at: 

  • Blood urea nitrogen (BUN) levels: Blood urea nitrogen refers to nitrogenous wastes that are circulating in the bloodstream. When the kidneys are not functioning correctly, this blood value can become elevated due to a decrease in the filtration rate of wastes by the kidneys. It can also be elevated if the animal eats a raw diet which is higher in protein than dry food diets. 
  • Blood Creatinine:Blood creatinine refers to the amount of creatine phosphate circulating in the bloodstream. Creatine phosphate is removed from the blood through the kidneys. Elevated readings of creatinine can indicate kidney distress. However, animals eating a raw diet will naturally have a higher level of creatine. 
  • Anemia:The kidneys produce a hormone known as EPO which stimulates red blood cell production. When the kidney function is decreased, the EPO output decreases too and this leads to anemia. This will appear on bloodwork as low red blood cell count. 
  • Urine specific gravity: Urine specific gravity will be determined by a urinalysis and will show the kidney’s ability to concentrate urine. With CRF, the kidney’s ability to concentrate urine decreases, making the urine look dilute, watery, or clear rather than a darker yellow color. Always opts for a urinalysis along with blood testing for pets with suspected kidney disease to get the clearest picture of your pets’ condition. 

Treatment

The traditional treatment for pets diagnosed with kidney disease is to switch them to a veterinary “kidney diet” which is a dry, low protein diet.  Not only do these diets NOT work, but they are a recipe for further health problems.

The job of the kidneys is to filter and eliminate protein wastes and so these diets were based on the approach that reducing protein levels will reduce waste products going through the kidneys, and thereby reduce the workload of the kidneys.  

The problem with this approach is: YOUR PET STILL NEEDS PROTEIN to support their health, so reducing protein in their diet is a recipe for a myriad of other health issues including muscle waste, other organ failure and much more.  Muscle wasting is often attributed to the kidney disease itself but it can also be a product of a low protein diet. 

The school of thought evolving today as we better understand the role nutrition plays in disease is to feed food that will support kidney and other functions, by feeding food that is high in moisture, less processed and contains better quality ingredients. So here are some things to consider in treating kidney disease:

Fluid therapy: Fluid therapy is usually the first line of treatment once a diagnosis of kidney disease is determined. Fluids will help to keep your pet hydrated and this will support kidney function. This, alongside a high moisture diet will keep them as hydrated as possible at all times. 

Moisture level of diet: As discussed in Part 1 of this article (link blog/help-us-stop-the-kidney-disease-epidemic-one-meal-at-a-time-),a diet devoid of moisture can make a really big mess when it comes to the long term health of your pet causing long term dehydration and an unmanageable work load for the kidneys. 

Dietary moisture content should always be increased in true cases of kidney disease to keep the animal properly hydrated. But there are still dry kidney diets on the market. These diets will work against you and will increase the amount of fluid therapy your pet needs on a daily/weekly basis. Prevention is the best bet by starting your pet on a high moisture diet right from day 1.

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Protein level of diet: Protein type and percentage should be considered carefully with animals who are in a later stage of kidney failure (Stage 3 and 4) along with protein quality. 

The amount of protein in the diet will affect the amount of nitrogenous wastes the kidneys need to process so for later stage kidney disease, we recommend that dogs eat a 50/50 meat to veggie ratio and cats to eat as many veggies as possible. Because cats are obligate carnivores that don’t have a particular love for vegetables, they sometimes don’t like to eat more veggies. For this reason, the most important thing is that your cat continues to eat as much as possible, making protein quality and hydration the most important factors for them. 

Protein quality: Simple. Feeding low quality protein will increase workload on the kidneys, even if you reduce the AMOUNT of protein. It will also put a more stressful work load on the kidneys to feed low quality protein even when it is fed in reduced amounts. “Kidney diets” containing low quality, highly process meat and meat by-products are not a suitable source of nutrition for a pet with kidney disease or any pet for that matter! In our opinion, high quality, minimally processed fresh protein diets are a much better option!

Phosphorus level: With kidney disease, excess phosphorus becomes hard or impossible to excrete from the body. Dietary phosphorus levels should be reduced where ever possible to help alleviate this.  With raw diets, boneless meats with and eggshell calcium supplement can be used to reduce the phosphorus levels but still provide enough calcium and phosphorus for body functions. Blood calcium and phosphorus levels will be monitored by your veterinarian and diet can be adjusted as needed. 

Sodium/potassium levels: Sodium and potassium levels should be closely monitored by your veterinarian as well. Potassium can become depleted in animals with CRF so dietary adjustments may be needed to address this. If there is depletion, your veterinarian may suggest increasing dietary potassium and then retesting the bloods. 

Essential fatty acid ratio: Omega 3 fatty acids have been shown to be a promising form of therapy for kidney inflammation. (1) Omega 6’s tend to have inflammatory effects when not balanced correctly with omega 3’s so it’s an important factor to consider when you’re formulating a diet, for any pet but especially those with CRF. 

Dietary antioxidants: Antioxidants will help to reduce oxidation of kidney tissue and can help improve kidney function in CRF animals. Vitamins C & E have been well studied in this regard. (2) (3) (4) There are lots of antioxidants that naturally occur in a balanced raw diet, including vitamins C and E.

Understanding Blood Results 

This is where we can geek out a bit! 

Dr. Jean Dodds, DVM from Hemopet in California recently completed a study on blood values of 200 raw-fed and dry-fed dogs. She was looking for indications that there may be different “normal” blood value ranges for each way of feeding. She discovered that raw fed dogs often have higher BUN, creatinine and hematocrit. In dry-fed pets, this has always been considered part of the clinical picture of kidney disease. But with raw fed pets, she suggests that different normal blood parameters should be considered depending upon the diet of the pet. Below are her findings:

TEST RESULT

RAW FED DOGS

 

KIBBLE FED DOGS

 

NORMAL VALUES

Hematocrit

 

51.0 ± 6.6 – 53.5 ± 5.6%

 

47.6 ± 6.1%

 

37 – 55%

 

BUN

 

18.8 ± 6.9 – 22.0 ± 8.7mg/dL

 

15.5 ± 4.7mg/dL

 

6 – 24mg/dL

 

Creatinine

 

1.20 ± 0.34mg/dL

 

1.07 ± 0.28mg/dL

 

0.4 – 1.4mg/dL

This is important to note when considering blood work for your raw fed pet since kidney disease can be falsely diagnosed in some cases. It’s important to find a veterinarian that understands that diet makes a difference when it comes to truly diagnosing kidney disease. 

So now you have the tools you need to assess your pet clearly with your veterinarian. If you’re not already doing so, we do recommend that you take your pet to a veterinarian who is knowledgeable about raw diets in order to avoid a misdiagnosis of kidney disease. 

 Click the link to read Part 3 of this article on the dietary holistic management of Chronic Kidney (Renal) Failure . 

References:

(1) Therapeutic Effects of Omega-3 Fatty Acids on Chronic Kidney Disease-Associated Pruritus: a Literature Review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5241408/

(2)  Vitamin C supplementation in kidney failure: effect on uraemic symptoms: https://academic.oup.com/ndt/article/26/2/614/1890777

(3)  New insight on vitamin C in patients with chronic kidney disease: https://www.ncbi.nlm.nih.gov/pubmed/21195931

(4)  Vitamin E may slow kidney failure owing to oxidative stress: https://www.ncbi.nlm.nih.gov/pubmed/9754323