Grain Free Diets – Harmful or Helpful?

Grain Free Diets - Harmful or Helpful?

If you go to any pet food store, or even search for foods online you will see claims of “Grain Free”, “Ancient Grain”, “Legume Free”, “No Corn, Wheat or Soy” plastered all over packaging for treats, dog foods, and even chews.

The question becomes – should I feed my dog a grain free diet? What are the benefits of grain free? What are the potential risks of grain-free? How do we weigh these risks and benefits to see if a grain-free food is the best option for my dog? Should I be worried about grains? Should I be concerned if my pet’s food contains grains, potatoes, peas, corn, wheat or soy?

I think the hardest part of this debate is that on the surface it seems like everyone is giving contradictory information – some people avidly are against grains, some are 100% for grains to be included in a diet.

So let’s break down some of these concerns and claims – and see which parts have some truth to them, and what parts are very much FALSE.


What causes food allergies - exposure, genetics and environmental trigger.

Some grains – like wheat for example – are rather high on the top allergen list, but other grains such as rice, oats, or quinoa are not common food allergens in dogs. However even given that wheat is a common allergen, it doesn’t mean that feeding wheat would CAUSE your pet to become allergic.

It is generally accepted that your pup needs three things to show clinical signs of an allergy: 1. Genetic predisposition, 2. Exposure to Allergen, 3. Environmental Trigger.

Another item of note is that the top allergens are also the top ingredients in pet food. Meaning that it’s very possible that the reason why Beef, Chicken, Eggs, and Wheat are on top of the list for dog food allergies is because they are the most popular, not the most allergenic foods.

The bottom line here and what I want you to take away from this section is – though some dogs will be allergic to grains, avoiding grains in order to prevent allergies is not really helpful.

If you do suspect your pup has food allergies, work with your veterinarian and after ruling out other conditions (like metabolic problems, hypothyroidism, and external parasites) do a food elimination trial. This trial may be done using a food that is grain-free, however it also may be done with a diet that is grain inclusive, it depends on what your pup has eaten in the past.


Irish Setter
Irish Setter – one of the only dog breeds known
to have gluten intolerance.

There is only one breed known to have gluten intolerance – Irish Setters – and possibly Boston Terriers. Gluten Intolerance is considered a genetic condition associated with these breeds. Other breeds do not have gluten issues, there is no research that suggests putting a dog on a gluten-free diet makes a significant difference to their health UNLESS it happens to be warranted for other reasons (eg dog is allergic to wheat).

But why has gluten become such a HUGE thing in the dog food industry?

Marketing to pet parents.

What you need to understand is that MANY pet food companies might not have a board certified veterinary nutritionist, or even someone with a degree in nutrition on staff – but they will have a marketing team.

Crazy right?

What this means is that pet food companies are here to sell you food – and will use trends seen in the human marketing world in order to sell products. Because it’s not the dog that chooses their food – it’s the owner – and oftentimes if the owner believes strongly in a certain lifestyle for themselves, this will reflect in how they choose food/products for their pets.

One thing I will mention here is that some people who have Gluten Intolerance have it so severe where they may need Gluten Free food for their dog just because someone in the home is allergic to gluten and may come in contact with the dog’s saliva – which can carry traces of whatever the dog ate. In these cases a Gluten Free food for a dog is 100% reasonable, even though for the dog it isn’t necessary.


Are grains on average less expensive than meat? Yes.

Are they just fillers? No. Grains do actually contain vitamins and minerals that are beneficial to dogs, and they can definitely be part of a complete and balanced diet.

Do all dogs do well on grains? No, of course not – every pet is going to be different, and some pets will do best with a higher/lower amount of grains in their diet. Or may not tolerate certain grains (or other ingredients) in comparison to others.

The main thing here is that each ingredient needs to be looked at individually in regards to your pup and how THEY respond to the ingredient or diet composition. If it doesn’t work for your pup – then don’t do it.


This is not true. Dogs definitely can digest carbohydrates – it’s just a different process than that of humans.

Pancreas secretes amylase into duodenum to digest grains.

The first difference is that we – as humans – chew our food, and while chewing we secrete salivary enzymes that start the digestion of carbohydrates. Dogs usually do not chew food items, most of the time they “gulp” foods, and they also do not secrete salivary enzymes that digest carbohydrates (aka amylase).

The fact that dogs do not chew their food actually brings up the second issue with carbohydrates – mainly that dogs cannot break down cellulose. Humans actually can’t either – so what we do to mitigate this is either grind/puree the carbohydrate to manually break down the plant cell wall. OR we cook the carbohydrates – which increases digestibility.

The section of the digestive tract in dogs that actually helps break down carbohydrates into glucose and maltose for energy is the duodenum. The duodenum is the first section of the small intestine after the stomach – in this section the pancreas releases digestive enzymes – one of which is used to help carbohydrate digestion.

Microbiome further breaks down carbohydrates.

We are now finding new research suggesting that carbohydrate digestion does not stop within the small intestine, but in fact continues into the microbiome of the large intestine – with certain bacteria (such as Prevotella) aiding in breaking down carbohydrates even further. We also are finding that dogs that eat different diet compositions will have different distribution of bacteria in their gut – researchers speculate this is because the different gut bacteria aide in the digestion of certain types of foods or nutrients.

The bottom line is that research has shown that startch within carbohydrates such as corn, and rice are more then 90% digestible in dogs if they are properly prepared – eg. cooking and grinding to break down the cell walls. So it’s actually more of a question of IF dogs NEED grains/carbohydrates rather is IF they can digest them.


This is true – dogs do not have a carbohydrate requirement. However dogs have evolved from wolves and do have 10 different genes that help them digest carbohydrates – making them 28% better at digesting carbohydrates than wolves. This makes them what is called a “facultative carnivore”.

So though dogs don’t NEED carbohydrates, they can be useful – this is especially true in certain medical conditions, or if a pet has a certain lifestyle.

What you should keep in mind is that anything that the body doesn’t use is excreted.

Meaning that if you give your dog MORE protein than they need. The rest is going to be just flushed out of the system.

Let’s talk LIFESTYLE for a moment here and how that affects protein needs in the dog…

In racing dogs they ran slower with fat content greater than 75%, and less than 28%. The ran best with fat between 31-39%. They also ran slower with protein content above 36% than with protein of 24%.

For sled dogs they did best with protein content above 40%. And beagles running 20 miles per day did best with fat content between 50-60%.

The lifestyle of a wolf is very active – on average wolves roam 20 miles (or more) per day. That kind of movement requires a lot of protein and fat to help fuel and recover from that kind of exertion.

For sled dogs who have similar lifestyles it is often recommended that they be fed very similar to wolves – with that high protein, high fat diet. And research looking at sled dogs has found that this composition provides peak performance for these dogs.

However for other dogs the same diet composition doesn’t yield these results. Most sprinting and working dogs through research have actually been found to do best on moderate to high protein, moderate fat, and moderate amounts of carbohydrates. 

Ideal Greyhound Racing dog food composition was Fat 35%, Protein 25%, Carb 40%.

Ideal Sled Dog ratios were Fat 50-60%, Protein >40%, Carbs 0-10%.

Based upon simple math to make Protein, Fat and Carbs = 100% of energy needs and previously mentioned study.

This shift in needs suggests that your pup’s lifestyle should be taken into account when choosing a food for your pup.

Most dogs do not run 20 miles per day. In my experience most urban dogs might get 5 miles of movement per day and with less activity comes less necessary protein – any remaining protein needs to be broken down, and then excreted by the system (usually in the form of urine). Now there is no research saying high protein diets are harmful to dogs unless they have other underlying conditions (think liver disease). However we also need to consider that it’s not necessary – meaning if a diet does contain carbohydrates – it is equally not bad for dogs unless they have certain underlying conditions (certain types of cancer).

The important part I want you to take away from this is that you should be feeding the dog in front of you, not trying to copy the dietary needs of another dog. Your dog has their own unique nutritional needs, and may do best on a certain diet composition over others – this is NORMAL.


This statement largely has more to do with the type of grain, the sourcing of the grain, and how the grain is grown. But yes – grains – like any non-organic food item can contain pesticides and be GMO. I think it is important to note here that any food product that is non-organic will contain pesticides – in the USA the EPA regulates and tests food products for pesticides and requires that they be below a certain limit in order to sell.

There are also ways to reduce pesticide load within food items – some of the main ways being…

Ways to Reduce Pesticide Load:
  • washing
  • scrubbing
  • cooking

There have been several studies looking at different cooking processes of meats and how they affect the overall pesticide load. Depending on the cooking process there is between a 1% to a 97% reduction in pesticide load in meat products after they are cooked.

Research looking at pesticides within rice found that by just cooking the rice pesticides were reduced anywhere from 20% to 97% depending on the pesticide in question. Meaning that by cooking food products we actually can reduce the amount of pesticides within the food item.

The same study found that by just washing the rice they found a reduction of 18 to 88% reduction in pesticides. Similar findings have been found in other studies looking at washing of vegetables, and rubbing fruits and vegetables dry with a paper towel.

What I want you to focus on here is that ALL food items if non-organic will contain some pesticides, the EPA does regulate how much is in the raw products, and once these products are placed in the food chain depending upon how they are processed going forward. If the non-organic food items are washed prior to use (in the case of produce/grains), wheather or not they are cooked, how they are cooked – will determine the overall amount of pesticides in the final product.

If you wish to avoid Pesticides avoiding grains is not really helpful – INSTEAD choose organic food items.


Since the 2018 DCM report by the FDA Grain Free Diets have been implicated in causing some dogs to develop a form of nutritional associated dilated cardiomyopathy – which is a heart condition in dogs.

Unfortunately research is still largely ongoing in this area – and scientists, nutritionists and cardiologists are working to get an answer as to if grain-free diets cause DCM. At this moment we still don’t really know the cause – and there are MANY potential factors that may by influencing why a dog might develop diet-associated cardiomyopathy.

  • Anti-nutrient factors in legumes or potatoes.
  • Lack of taurine for dogs that need supplemental taurine
  • Novel Protein Digestibility
  • Fiber content
  • Genetics
  • Or a combination of factors!

According to the board certified veterinary nutritionists from Veterinary Nutrition Consulting:

The FDA is investigating the relationship between canine Dilated Cardio Myopathy (DCM). The relationship or mechanism has not yet been clarified. Dogs do very well on grains and there is no nutritional advantage to feeding a grain free diet.

You can find a full breakdown on DCM in dogs on my blog – that covers the current research and considerations related to diet and DCM.



Mycotoxins are poisonous compounds produced by certain species of fungi found in contaminated grain.

Mycotoxins are a legitimate concern that is mostly contained to grain products in both the human and the pet food world. In the human food chain there are multiple points of quality control that have been implemented in order to catch and prevent Mycotoxin contamination. However multiple repeat studies have STILL found contamination within the human food chain, thus it is no surprise that we see the same contamination – but in higher numbers – within our pet food chain.

Multiple studies on pet food have found mycotoxins within our pet food chain, and even today we see recalls pertaining to Mycotoxins on a regular basis, the most recent of which was in October of 2020 where several brands of dog food were recalled due to aflatoxin.

It should be noted however that good sourcing, storage and quality control of ingredients within the pet food chain CAN prevent this contamination

ASK your pet food manufacturer if they regularly test for Mycotoxin contamination within their grain products, and if they are storing them correctly prior to use!


My personal belief is that grains or any type of carbohydrate are not BAD. They are not toxic to dogs and there is no evidence to suggest they CAUSE disease. However, I think it’s important to realize that all dogs are individuals and some dogs may need more/less carbohydrates within their diet due to digestibility issues, medical conditions, or just managing their lifestyle/activity level. 

All diet compositions are not appropriate for all dogs.

Let me give you all some examples… 

My pup Ash has -what we believe is- borderline Pancreatitis. He cannot tolerate higher fat diets, and most high protein diets also contain more fat that he can handle. Thus for him using carbohydrates to offset this – along with a variety of fruits, and vegetables allows him to meet all his daily nutritional requirements without causing issues.

But some dogs will THRIVE on a higher protein, low carb limited ingredient diet. This is especially true for dogs with IBD – dogs with IBD suffer from small intestine inflammation. This inflammation to the small intestine leads to loss or damage to the mucosal enzymes within the gut lining. These enzymes are usually responsible for a majority of carbohydrate digestion. Without them dogs have issues with carbohydrate digestion – leading to pain, loose stools, gas, etc.

I hope that this gave you a good overview on the Grain-Free debate as a whole and gave you some information and tools that you can use in order to decide if you should feed a grain-inclusive diet or grain-free diet to your pups.

I am going to just leave you with a quote I found from the board certified veterinary nutritionists on Pet Diets “There is not one thing wrong with feeding grains to dogs.”

If you are interested in more information about canine health, nutrition and wellness make sure to follow me on Instagram/Facebook or subscribe to my email list below and receive your free ebook on how to do an at home physical assessment on your pup!


Streit E, Schatzmayr G, Tassis P, Tzika E, Marin D, Taranu I, Tabuc C, Nicolau A, Aprodu I, Puel O, Oswald IP. Current situation of mycotoxin contamination and co-occurrence in animal feed–focus on Europe. Toxins (Basel). 2012 Oct;4(10):788-809. doi: 10.3390/toxins4100788. Epub 2012 Oct 1. PMID: 23162698; PMCID: PMC3496989.

Böhm J, Koinig L, Razzazi-Fazeli E, Blajet-Kosicka A, Twaruzek M, Grajewski J, Lang C. Survey and risk assessment of the mycotoxins deoxynivalenol, zearalenone, fumonisins, ochratoxin A, and aflatoxins in commercial dry dog food. Mycotoxin Res. 2010 Aug;26(3):147-53. doi: 10.1007/s12550-010-0049-4. Epub 2010 Mar 23. PMID: 23605379.

Boermans HJ, Leung MC. Mycotoxins and the pet food industry: toxicological evidence and risk assessment. Int J Food Microbiol. 2007 Oct 20;119(1-2):95-102. doi: 10.1016/j.ijfoodmicro.2007.07.063. Epub 2007 Aug 19. PMID: 17889389.

Bryła M, Waśkiewicz A, Podolska G, Szymczyk K, Jędrzejczak R, Damaziak K, Sułek A. Occurrence of 26 Mycotoxins in the Grain of Cereals Cultivated in Poland. Toxins (Basel). 2016 May 25;8(6):160. doi: 10.3390/toxins8060160. PMID: 27231939; PMCID: PMC4926127.

IOSR Journal Of Environmental Science, Toxicology And Food Technology (IOSR-JESTFT)
e-ISSN: 2319-2402,p- ISSN: 2319-2399. Volume 6, Issue 2 (Sep. – Oct. 2013), PP 43-53

Shakoori A, Yazdanpanah H, Kobarfard F, Shojaee MH, Salamzadeh J. The Effects of House Cooking Process on Residue Concentrations of 41 Multi-Class Pesticides in Rice. Iran J Pharm Res. 2018 Spring;17(2):571-584. PMID: 29881415; PMCID: PMC5985175.

Michaels B, Gangar V, Schattenberg, Blevins, Ayers. Effectiveness of cleaning methodologies used for removal of physical, chemical and microbiological residues from produce. Food Service Technology. 2003.

Muresan C1, Covaci A2 , Socaci , Suharoschi R , Tofana M , Muste S and Pop A. Influence of Meat Processing on the Content of Organochlorine Pesticides. Journal of Food Processing & Technology. 2015.

Richard C. Hill, The Nutritional Requirements of Exercising Dogs, The Journal of Nutrition, Volume 128, Issue 12, December 1998, Pages 2686S–2690S,

Wu, G. D., et al. “Linking Long-Term Dietary Patterns with Gut Microbial Enterotypes.” Science, vol. 334, no. 6052, 2011, pp. 105–108., doi:10.1126/science.1208344.

About the Author: Nikki is a Registered Veterinary Technician (Veterinary Nurse) and Dog Mom with over a decade of experience with dogs and cats. Since graduation from college (BS Biology, Dip. Animal Nutrition, AS Animal Science) she has adopted two mixed breed dogs – Ranger and Ash, and has focused her time learning about pet food and nutrition.

Nikki shares information on a range of dog nutrition topics: from how to create a homemade complete and balanced dog food recipes, to how to choose a dog food. Nikki strives to give dog parents the information they need in order to make the best nutrition decisions for their pup!

You should receive your Free Dog Food Recipe Ebook within 24 hours of subscribing! Make sure to check your spam folder. The recipe ebook is over 90 pages long so make sure you have a good internet connection when you go to download it. Afterwards you will receive weekly Canine Nutrition Updates every Tuesday on different topics related to canine nutrition & homemade dog food!


Personalized Pet Nutrition Consultation

Leave a Reply