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Interview with a scientist: The effects of peas and pulses fed to dogs in a grain-free diet

If you talk to any dog owner out there, they will have a different opinion on grain-free diets and the use of peas in pet food. In 2018, the FDA released a statement that grain-free diets could be linked to a cardiovascular disease called dilated cardiomyopathy (DCM). As a result, the media and consumers went wild with this information. As a result, a lot of misinformation was circulated through the pet community. 

Two dogs eating together from their food bowls Two cute dogs eating dinner from their food bowls on the floor of their home dog eating stock pictures, royalty-free photos & images

Since then, the FDA has retracted their initial statement, citing lack of evidence for a correlation between grain-free diets and DCM. So why are there still so many mixed feelings about grain-free diets? Are they nutritious and healthy or potentially harmful? 

We decided to consult a scientist who is part of the research that is directly working to answer these questions. Chloe Quilliam is a Master’s candidate at the University of Saskatchewan, Western College of Veterinary Medicine. Her research is in dog nutrition with a specific focus on the use of peas and other pulses in pet food. Along with her team of researchers, she recently published a study on the effects of feeding grain-free diets on digestibility, blood sugar and heart health in dogs.

What is the difference between a grain-free and grain-containing diet?

Quilliam: “A grain-containing diet uses cereal grains as its main carbohydrate source. These grains are typically sources like rice, corn or barley. Conversely, grain-free diets use potatoes and/or pulses such as lentils or peas as the main carbohydrate source in the diet. The difference between grains and pulses is that grains are a hard seed and do not have an attached hull. Whereas pulses produce a seed in a pod that is dried and harvested. Pulses are beneficial to use in dog diets as they are high in protein, fibre, vitamins and minerals. The high fibre fractions are beneficial as they can increase satiety, allowing dogs to stay fuller for longer.”

Green fresh pea seeds and branches on black. Space for text. View from above Green fresh and dry pea seeds and branches on black concrete background. Space for text. View from above peas stock pictures, royalty-free photos & images

Are peas and other pulses toxic or poisonous to dogs?

Quilliam: “Not at all. No portion of pulses are toxic to dogs and are safe for them to eat when fed in a normal, moderate amount.”

What is DCM?

Quilliam: “DCM or Dilated cardiomyopathy is a disease that occurs within the cardiac heart muscle, which results in improper heart functions and poses a risk to pets. DCM occurs when the heart muscle degenerates and the heart wall thins. As a result, there is an enlargement of the heart, typically seen greatly within the left ventricle (the thicker heart wall). There can be many causes for this disease, as some breeds are predisposed to it. However, there is a possibility that nutrition could also be a factor, especially for dogs that are not predisposed to this condition.”

Heart disease vector concept in flat illustration style

What are cysteine, methionine and taurine and why are they important?

Quilliam: “Cysteine, methionine and taurine are nutrients called amino acids, which are the building blocks of protein. Dogs are able to make taurine in their body with cysteine and methionine, which is why it is important for their diets to contain these. Taurine is not considered essential in dogs as of right now, but it is beneficial as it promotes heart health in dogs. Pulses are low in taurine and limited in cysteine and methionine.”

Do dogs need fibre?

Quilliam: “Fibre in dog food is very similar to that of a human diet. It is beneficial to promote gut health and also increases satiety in dogs, allowing them to feel full for longer periods of time. As a result, fibre can be beneficial to help manage weight. Compared to grain, peas and other pulses are higher in not only protein but fibre as well, which can be beneficial in dog food.”

Large group of wholegrain food shot on rustic wooden table Top view of wholegrain and cereal composition shot on rustic wooden table. This type of food is rich of fiber and is ideal for dieting. The composition includes oat flakes, brown rice, dried corn,spelt, hemp seeds and flax seeds. Predominant color is brown. XXXL 42Mp studio photo taken with SONY A7rII and Zeiss Batis 40mm F2.0 CF fibre stock pictures, royalty-free photos & images

What is meant by the term glycemic index and postprandial glucose response?

Quilliam: ”Glycemic Index is a value given as a way to determine how greatly food will impact blood sugar levels. Diets with a higher glycemic index value will cause a greater change in blood glucose levels, while diets with a low glycemic index will cause a lesser change in blood sugar levels. Glycemic response is a tracking of how blood sugar levels respond to a diet after consuming at multiple time points. Diets that are high in fibre are generally digested slower, resulting in a slow release of glucose into the bloodstream, reducing major spikes in blood glucose.” 

What is digestibility and why is it important?

Quilliam: “Digestibility is the study of nutrients in diets to determine how much is absorbed and utilized by the body versus how much is excreted in feces. It is important to study digestibility to ensure enough major nutrients are available to dogs in order to ensure that they are absorbing enough nutrients to meet dietary requirements. If an animal is excreting too many nutrients there might be too much resistant starch in the diet binding nutrients.”

Why is your study important and how does it impact the pet community?

Quilliam: “Our study is important to determine the short-term benefits and short-comings of pulse-based diets as a preliminary study before conducting a long-term study. This study was important to determine the benefits of pulse-based diets on glycemic response but also to see how the fibre could impact nutrient digestibility and plasma changes in sulfur-containing amino acids.” 

How did you conduct your study?

Quilliam: “8 research dogs were fed six different test diets (5 grain-free diets and 1 grain-containg diet), ranging in fibre content for 7 days. In between each diet the dogs were fed a commercial diet as a wash out to “reset” before starting to feed each test diet. After feeding the dogs for seven days poop samples were collected to determine digestibility and blood plasma was collected to determine plasma amino acid content. The beagles were also fed small, calculated amounts of the test diet and had blood drawn at multiple time points to determine the glycemic response of each diet.”

scientist illustration woman looking though microscope

What did you find?

Quilliam: “Key findings were that the grain-free diets produced a low-glycemic response in dogs, however these diets also had increasingly reduced nutrient digestibility as fibre content increased across the diets. Seven-day feedings did not seem to majorly or negatively impact taurine levels in dogs, but long-term feeding trials should be conducted to further examine this.” 

What is the take home message of the study?

Quilliam: “The take home message is that pulse-based, grain free diets do have some benefits, especially in the short-term. Specifically being used to help lower blood sugar and promote satiety (fullness). However, dogs are fed their diets on a long-term basis, pushing the need for a long term study to further explore if there are any effects of pulse-based diets on heart health.”

What is your view on grain-free diets and the FDA statement on DCM?

Quilliam: “I think that grain-free diets have their benefits in regard to glycemic response, but do have their trade-offs with nutrient digestibility. However, if formulated well, this shouldn’t be a major issue. I personally think the initial FDA statement was rushed and based on poor science. It is difficult to make a true correlation between grain-free diets and DCM, particularly because while pulses are lower in methionine, cysteine and taurine, these amino acids are often still supplemented in the diets. However, it is still important to study this issue to help provide pet owners with clarity and to truly determine the safety of these diets on our pets.”

Golden Retriever and licking it's nose

Quilliam will be conducting a long-term feeding study to further examine the effects of pulses on glycemic index and heart health. Results which we look forward to reviewing! If you would like to take a closer look at her short-term feeding study titled The Effects of 7 Days of Feeding Pulse-Based Diets on Digestibility, Glycemic Response and Taurine Levels in Domestic Dogs, click here!


Beagle eating kibble from silver bowl
Beagle eating kibble from silver bowl

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