In Defense of Grains

I like to think of myself as a moderate in all things veterinary nutrition. Avoid known toxins, avoid any particular food or ingredient that your individual dog or cat does not seem to tolerate, feed a balanced diet in an amount to maintain a healthy body condition, and try not to tie your pet food choices to someone else’s ethical eating standards.  Especially with the recent attention on grain-free diets, it is important for caregivers to understand when market trends, rather than animal nutrition, are shaping their dog or cat’s diet.

Be smart like Penny and educate yourself about pet food marketing.

So where did the idea that grains are somehow bad come from?

Simple. It came from pet food companies that were trying to distinguish themselves in a competitive marketplace. It had nothing to do with quality, food safety or nutrition and all about selling pet food.

Corn and other whole grains somehow became the “wrong” foods to feed dogs and cats about 10 years ago. My personal theory was that this shift in pet food ingredients was a combination of: 1) the pet food recalls in 2007 due to  contaminated wheat and rice ingredients;  2) an increased awareness of “hidden allergens” in people foods starting in 2004 when labeling laws for people foods required human food manufacturers to start listing all potential food allergens whether intentionally added or not; 3) the availability and promotion of what was then a new category of plant ingredients, the pulses (i.e., peas and other legumes), starting in 2010; and 4) smaller pet food marketing companies trying to make a name (and a lot of money) by distinguishing themselves from the established competition.


We grow a LOT of delicious corn in the middle.

Companies big and small like to highlight the differences between their foods and their competitor’s products, something that has been done from the beginning of food marketing times. Since the vast majority of over-the-counter dog and cat foods were and still are largely manufactured in the Midwest where corn and wheat are grown and easy to get at a good price point, smaller companies that targeted pet owners willing to pay more for their pet food began using less common and more costly pet food ingredients like potato and peas.  The problem with the explosion in sales of grain-free pet food is that these ingredients are relatively new to the pet food marketplace and don’t have the decades of feeding trials and nutrient and digestibility standards to demonstrate that they are safe for long-term, chronic feeding.

Everyone loves Porkchop and her side of corn.

This Nutritionist’s quasi-concern with corn.

I don’t have any concerns about corn as a stand-alone food or ingredient in pet foods. Corn is high in the essential-for-life omega-6 fatty acid linoleic acid (LA) so it makes balancing home-cooked diets easier, but is also practically devoid of the essential-for-optimal-skin-health omega-3 fatty acid alpha-linolenic acid (ALA) so by itself isn’t a complete food. ALA was not recognized as a nutrient requirement until publication of the National Research Council’s Nutrient Requirements for Dogs and Cat book in 2006 and it still hasn’t been incorporated into the AAFCO Model Bill and Guidelines for pet food manufacturers. Meaning diets that are made by manufacturers who use large amounts of corn (high in LA and variable digestibility depending on quality standards of the manufacturer) that don’t follow new developments in the field of dog and cat nutrition can legally sell diets that are listed as “complete and balanced” that are potentially imbalanced in essential fatty acid levels and may cause dull dry skin, itching and flaking and excessive shedding in some animals. This isn’t an “allergy” to corn, or even an indication that corn is bad, but that the essential fatty acids in that diet aren’t balanced for that individual dog or cat’s needs.


Not all itches are fleas and allergies.

What about gluten?

Gluten is just the generic term for protein found in plants. People with celiac disease are sensitive to the specific glutens found in wheat, rye and barley called gliadin and glutenin, but have zero problems with the gluten found in rice or corn. There is some evidence that Irish setters and soft coated wheaten terriers may have similar gliadin and glutenin sensitivities, but this condition has not been seen or proven in cats or other dog breeds. The disconnect with pet foods is that from a legal labeling perspective  “gluten” is the generic food science definition of a plant protein (i.e., rice gluten, wheat gluten, corn gluten) and is what shows up on labels even though the physical structures of each of these plant proteins are all unique. Over the last decade, small and medium-sized pet food marketing companies have started to exploit peoples lack of awareness of these differences to demonize all grains in pet foods in order to sell more of their own “grain-free” products.

Raider was sweet and adorable, though his beef- and flea-allergy dermatitis were not.

What about dogs and cats with grain allergies?

The majority of the gastrointestinal food sensitives that I see and treat in dogs and cats are not true allergies. True allergies are eosinophil mediated type III hypersensitivity reaction resulting from an antigen-antibody complex that triggers a cascade of immune-mediated problems resulting in inflammation and dysfunction of the skin or intestinal tract. If your dog or cat has an allergy to any given ingredient then absolutely avoid that ingredients, but what I tend to see are mostly adverse food reactions caused from feeding poorly digestible diets or ingredients that alter gastrointestinal microflora causing bacterial dysbiosis (imbalance of “good” vs “bad” bacteria that are normal inhabitants of the intestinal tract). It is these bacterial-induced changes on the environment in the digestive tract that affect its function (nutrient absorption and holding poop until the appropriate time and place) that cause the signs that can keep dogs, cats, and their caregivers up at night (literally and figuratively).

What are the benefits of including whole grains in a diet?

Grains like barley, wheat, rice and corn provide essential nutrients like protein, amino acids (the building blocks of protein), +/- the essential omega-6 fatty acid linoleic acid (essential for skin and coat health), vitamins like thiamin and riboflavin (B1 and B2), and minerals like magnesium and selenium. They also provide a source of dietary fiber and while fiber is not considered “essential for life” and is not included in the AAFCO nutrient list for dog and cat diets, is actually essential for normal intestine health and function. As I’ve written before in this blog, fiber, especially fermentable fibers feed the gut bacteria that feed the colon cells and keep them happy and healthy. And there it is one thing that we can all agree on is that eyes are the windows to the soul and poop is the herald of health.

Playful Penny loves all foods and has the healthiest poops of any dog she known.

The bigger picture on grains …

We grow a lot and eat a lot of grains and cereal crops in the United States whether as individual ingredients or fractions of ingredients (think rice flour and soy protein). These are less expensive sources of nutrients than animal proteins so companies who are trying to reduce costs and maximize profits (which is ALL OF THEM) will use easily sourced plant-based ingredients whenever possible. The last 50+ years of commercial pet food production has shown us that these foods are safe and nutrition sources of nutrients for dogs and cats when processed and stored correctly. Corn, wheat, sorghum, barley, and rice have been used successfully for decades in dog and cats foods, they are palatable and digestible by both dogs and cats, but, depending on the amount and quality of the plant-based ingredients digestibility may not be great and since digestibility is inversely related to poop volume:  more digestible = less poop; less digestible = more poop.

If your individual dog or cat has a known sensitivity to any particular ingredients (plant or animal sourced) then absolutely avoid that particular food in your individual dog or cat’s diet. This is also true if that dog or cat is sensitive to chicken, emu, elk, or quinoa. Dogs and cats can develop sensitivities or allergies to any protein, whether it comes from a plant or an animal. I realize all of these statements make me unpopular among certain self-appointed pet food advocacy groups and individuals, but aside from foods that contain known toxins or are harmful to dogs and cats, there is no one perfect diet or set of ingredients for each individual dog or cat.


Happy Feeding!

Lisa P. Weeth, DVM, MRCVS, DACVN

22 thoughts on “In Defense of Grains

  1. Hi Lisa and thank this new article!
    I find very interesting the meaning of gluten as a general term for plant-origin proteins.
    Most people recognize it as a wheat exclusive component although maize gluten is clearly a product of maize industry.
    Where (book, paper,..) could I find a definition of gluten that you write about?
    Thanks a lot!


    • Hi Jose,

      Thanks for reading and taking the time to post a question/comment. The AAFCO publication is a good place to start for ingredient definitions and there is a lot of information on their website without you needed to spend the $$$ to purchase the 2018 book:

      Most of what goes into pet foods are “by-products” of the human food industry. One of my favorites is a dog food that claims “no by-products” but uses “peanut hearts” in their recipes. Peanut hearts are “by-products” of the peanut butter and peanut oil industries and are removed during processing because they impart a bitter flavor on these people foods. Reduce, reuse, recycle!



  2. Thanks for an informative post! What about grains or gluten for diabetic cats (or dog)? When our kitty was diagnosed, we found, which advised Fancy Feast that didn’t contain wheat gluten. And so much of dry cat food contains corn or some starch that obligate carnivores don’t need.


    • Hi Lin,

      Thanks for reading and taking the time to write a comment/question. For relatively uncomplicated feline diabetes I do try to reduce total carb intake whenever possible and canned, low carb diets are my preferred way of feeding these patients as well. You are correct that dry foods will in general have higher total carb contents compared to wet food. Carbs are not dietary requirements for cats (or dogs for that matter!), but are ‘required’ to make the dry food form the dough that will become the kibble. If I can reduce their intake I will, but sometimes I work with patients that have other medical issues, like cats with advanced kidney disease that need a lower or at least controlled protein intake, and we are stuck needing to feed a higher carb diet to manage the additional diseases and then we adjust insulin doses accordingly.



  3. Thank you so much for writing this article! Your sane perspective and expert knowledge is just what we need. Shared it on the VetTechLife Facebook page and the response is awesome. So far 8000 have been reached; 48 have shared and 56 have reacted.


  4. I definitely fell prey to the grain-free dog food craze a few years ago when choosing a food for my new puppy. He is now three, and still eats the (non-puppy version of the) same grain-free food that I chose back then. We are all very happy with it–he gobbles it down and his digestion, ahem poop, is regular and looks great and solid and he really never has any tummy issues. However, I recently read an article suggesting that later-in-life cardiac problems may be correlated with grain-free diets, but it is pretty early to be able to tell for sure. So my question is, do I switch my dog back towards a grain-containing diet even though he is doing great on his current food? He does not have any allergies or sensitivities and I know for sure that he can tolerate wheat and grains, as he receives scraps of healthy-for-him people food on occasion. Do you have any advice on whether to switch a dog for “no reason” since he was originally put on his current diet for “no reason” as well?


    • Hi Berry,

      Thanks for reading and taking the time to post a comment/question and I am glad to hear that your pup has been doing so well on his diet. Part of the answer to your question is based on your individual dog and part of the answer is based on the diet. If he is a large breed (>50lb adult weight) and is eating a dry GF diet made by one of the larger pet nutrition companies (e.g., listed in alphabetical order: Hill’s/Science Diet; Mars, also includes Pedigree, Royal Canin, Eukanuba; Purina, also includes ProPlan, Merrick) I would be less worried. Also if he is a large breed dog and is eating a dry GF diet from the small to medium pet food company that supplements with taurine or methionine (one of the precursors to taurine), or has a crude protein level at 30% or higher, I would also be less worried. But … if the diet is made by a smaller company, is lower in crude protein, and is not supplemented and/or he is a large breed or one of the smaller breeds with a predisposition to heart problems (such as Cockers or Cavalier KC Spaniels) then even if he outwardly looks fine I would change the base diet. You could also measure plasma and whole blood taurine levels to verify his current status before deciding on a diet change. I know that wasn’t a very specific answer but I hope it helped anyway!



  5. Thank you for this info! We have 3 Great Danes and we have been feeding grain free diets. My 7 year old has suddenly come up with a heart murmur. Slightly enlarged heart. Meanwhile my Great Dane community has started becoming aware of the grain free diet concerns. I have been doing research and I will be switching out their food and I have added supplements to help with what’s been missing. My younger Dane 2 years old is constantly eating things to bulk up her diet, ie, paper towels, tissues, lots of grass! She always seems hungry as well. I have also split their meals into 4 x daily to avoid the bloat. Total intake is 6 cups daily. They are all healthy weights. I’m wondering if going with a diet that includes grains might help her? It’s possible she is just one of those dogs that enjoys eating paper?


    • Hi Betty,

      Thank you for reading and taking the time to comment and I’m sorry I missed your message until today. Some dogs (and cats!) are just weird and like to eat a range of non-food items so the paper eating by your 2 year old could be behavioral. One of my old Labs loved eating and shredding toilet paper and we didn’t dare keep candles in the house because he would swipe them and eat them wick and all. But, eating non-food items can also be a sign that the dog has a bit of an upset stomach (gastroenteritis in vet-speak) so I wouldn’t ignore it altogether especially is it hasn’t gotten better with the diet change, or if she starts to lose weight or have more overt GI signs (like vomiting or diarrhea). Then I would have her checked out by your regular GP vet. Depending on the brand of grain-free diet you were feeding in the past the main non-heart related issue that I’ve seen in practice are intermittent diarrhea and increased gassiness. This could be due to the diets using things like potato and tapioca, which are low in fiber overall and what fiber is there is fermentable and can cause a bacterial imbalance and colitis, or the ingredients that are being used being poorly digestible, which again can cause a bacterial imbalance and colitis. Either way if it is a dog-diet mismatch the easiest change to make is with the diet.



  6. Pingback: » The Facts About Grain-Free Diets and Canine Dilated Cardiomyopathy: Part One – The Evidence (and How It Has Been Misinterpreted by Leading Veterinarians) - The Optimal Dog

    • I applaud the enthusiasm certain individuals have for dog and cat nutrition, but, at the risk of tooting mine and Dr. Freeman’s horns, advanced education, clinical experience, and knowledge of both veterinary clinical nutrition and the broader pet food industry are pretty compelling reasons to listen to one source over another. And as I stated in the opening line of the post being critiqued by certain individuals, I think of myself as a moderate in all things veterinary nutrition. Feed your dog or cat a balanced diet, avoid harmful or toxic foods, and don’t be swayed by food trends demonizing one group of foods while trying to sell you another.

      Dr. Weeth


  7. As a member of FB’s DCM group, I have noted the fear & confusion in many of the comments. One example is the term “balanced diet” without knowing what it means. I posted that I add homemade fish stew to a fish kibble (GF) for my Portuguese Water Dog (to reduce carbs & calories). Someone asked how I know if it’s “balanced” & I don’t know other than using common sense. Is there a website or app that figures out if the ingredients would constitute a balanced diet added to kibble?

    My Fish Stew = 2 lb. Codfish, veggies (32 oz green beans, 3 zucchini, 2 sweet peppers, 2 cup carrots), 3 apples, 15 oz can of plain pumpkin, 1/2 cup brown rice, 1/4 cup ground eggshells & 1/4 cup olive oil = 12 cups (24 servings: 1/2 cup stew + 1/2 cup of fish kibble). Daily: 1 C stew (250 kcal) + 1 C kibble (400 kcal) + 10 training treats (50 kcal) = 700 total kcal.


    • Hi Eva,

      Thanks for taking the time to post a question and comment and I bet your pup looks forward to meal times every day!

      Without doing a more thorough evaluation of your homemade fish stew and knowing a few more details about your current diet (e.g., are those uncooked/raw weights or cooked? what brand and type of kibble?) there could be a few essential nutrient deficiencies in what you are currently feeding. Commercial dry and canned dog foods are (or at least are supposed to be) formulated to provide all of the essential nutrient in one meal, assuming that the dog is eating close to its expected energy requirement give or take 15-20% in either direction. Most commercial pet foods have enough “overages” in nutrient levels though that even if you fed 2/3 of intended amounts to your pup they would still be getting adequate (even if not optimal) amounts of the limiting nutrients. The exceptions being certain breed that may have specific nutrient requirements (the essential fatty acids linoleic and alpha-linolenic acid are two examples of this) that may be higher than the “typical” adult dog and or dogs that have an increased demand for certain nutrient due to their overall health status.

      For my consultations I have a program that I use to evaluate recipes that draws from the USDA Nutrient Database and compares to both AAFCO ad NRC recommended intakes and you could do a similar process by going to (the commercialized version of the USDA Database) and then compare to an example of the AAFCO profiles. Without doing a deeper analysis of the recipe for your specific dog I can tell you that the vast majority of homemade diets that I’ve evaluated (whether developed by a GP vet, breeder, caregiver, or pet store owner) are often not high enough in calcium (though likely covered in yours); deficient to sub-optimal in linoleic and alpha-linolenic acids (the essential omega-6 and omega-3 fatty acids, respectively), olive oil is high in oleic acid (a non-essential omega-9) but is typically not enough by itself; is deficient in a number of trace minerals, like iodine, copper, iron and zinc; and while most of the vitamins are typically covered, E and B12 are often too low. Your pup is getting just over half of his calories from the dog food and may be ok in a number of these depending on the base diet, but it may be worth having your vet or a vet nutritionist double check to make sure nothing else is needed.



      • Thank you for being so generous with your time & advice, Dr. Weeth. I will definitely check out that website & hope to better understand what needs to be added to the fish stew. Other than canned green beans & pumpkin, the rest is fresh/raw when it goes in the crockpot to cook on low for a couple of hours. Forgot to mention the fish oil gel in each meal of stew & sardines for a special treat after agility practice. I made a topping of chopped calf liver with a few veggies (no peas or potatoes), but haven’t done that in a while.

        My vet is happy with the fish stew routine because it helps control weight. He had her on canned Science Diet for 6 mo. to lose weight, but she gained so much weight that he recommended a thyroid test, which was expensive & came back normal. I finally read the ingredients on the can (using a magnifying glass) & realized corn was one of the first 5! That’s when I stopped feeding her that stuff & stopped obsessing over her food, too.

        Where I grew up, corn was used to fatten cattle & hogs to make the meat tastier & more profitable. I raised 2 kids who grew up to be healthy & strong adults without any nutrition input from doctors, including my husband & father-in-law. I figured it can’t be that difficult do the same for my dog. After 6 mo. on my fish stew & kibble combo, her weight & skin allergy issues went away. The vet has been impressed & even asked for the recipe. 😉


      • Sounds like you hit on a good combo for your pup! Stew-type foods are great for calorie control since the extra water can help pups (and cats!) feel full. And if sardines and liver have been rotated in and out in the past (even if less frequently now) you’ve probably been able to cover most of the essentials over time. Sardine (especially if bone included) are great sources of iodine, calcium, and vitamins D and B12, and liver has vitamins A, D, B12, as well as copper, and zinc. We just need to be careful with liver and I typically either use a small amount daily or add it in 2-3 times a week. The vitamin A levels can be quite high even in calf liver and reach toxic levels if included daily. I suspect you’ll find that when you compare number you are pretty close, but definitely double check. Certain deficiencies can take months to years to develop and we want you to be cooking for your pup for years to come. 😉

        Happy cooking!


  8. Forgot to answer your question about kibble. The first few years I tried several brands ~ Taste of the Wild, Merrick, Acana ~ with meat, usually chicken. I began eliminating chicken & skin allergies improved. I stayed with Acana’s 2 kinds of fish until the DCM issue rose. For past few months, I’ve tried Fromm’s Salmon & Farmina’s Codfish – both grain free w/taurine added. Until the FDA completes its study, I’m sticking with Farmina’s fish.

    Thanks again, Dr. Weeth. You have been most kind.


    • Hi Natalie,

      Thanks for reading and taking the time to write a comment. I’m not advocating that cats should be fed only corn, just noting that cats have the ability to digest moderate amounts of properly cooked carbohydrates and that some of them (especially my in-laws’ cat that liked her occasional corn-on-the-cob treat) even like the taste and texture. Cats are obligate carnivores, which means they require certain essential nutrients that are naturally occurring in animal meats, but that does not mean they can ONLY eat animal meat just that it needs to make up the largest proportion of their diet. Cats in the wild (whether domesticated or wild-type) will ingest small amounts of plant matter (up to 15% of their daily calorie intake) as the stomach contents of their prey. And with certain medical conditions, such as kidney disease, having a non-protein source of calories is extremely beneficial to helping that cat feel better and slow progression of the disease.

      Hope that helps clarify things!
      -Dr. Weeth


  9. Pingback: Update on Diet-Associated Dilated Cardiomyopathy (July 2, 2019) | weethnutrition

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