The Risks of Going Vegan for Your Pets

STORY AT-A-GLANCE

• The ultraprocessed pet food industry, in part in response to vegetarian and vegan pet parents, is focused on finding ways to create non-meat plant-based diets for pets, especially dogs
• Dogs are in the Order Carnivora. As scavenging carnivores, they do not have a carbohydrate requirement. Commercial vegan pet foods contain primarily high starch carbohydrates, plus long list of synthetic vitamins, minerals, amino acid powders and processed vegan protein concentrates to meet canine minimal nutritional requirements
• Every human involved in the care and feeding of animal companions must realize we have an ethical responsibility to nourish them in a way that best resonates with their physiology, and not based on our personal dietary preferences
• Ultraprocessed vegan pet foods are potentially more detrimental. Unless plant-based pet foods are certified USDA-organic, they are likely contaminated with herbicides and pesticides, and can contain high amounts of anti-nutrients and potentially damaging compounds including phytates, trypsin inhibitors, saponins, oxalates and phytoestrogens that can negatively impact health, if fed as a sole food source

The ultraprocessed pet food industry is nothing if not persistent when it comes to promoting ingredients and diets that are neither species-appropriate, nor nutritionally optimal for facultative carnivores (dogs) or obligate carnivores (cats). An example is a recent PetfoodIndustry.com article headlined "It IS possible to produce balanced vegetarian/vegan dog diets," which kicks off with this:

"Plant-based proteins have become strong marketing claims for pet foods and treats. To take it a step further, non-meat or no-animal protein options are making their entry into pet food — especially dog foods. Traditionally, these foods have been positioned on the notion that the dog is a carnivore and needs animal-based ingredients to thrive.

It is certainly easier to formulate a nutritionally complete diet for dogs using animal-based proteins and fats. However, the dog is an opportunistic omnivore and capable of surviving on a plant-based, vegetarian or vegan diet, especially our spoiled urban couch potato dogs. We do have the ability to formulate and produce these diets. How is this possible and what special ingredient considerations must be considered?"

Notice there's no mention of cats here, because they don't yet dare try to spin the natural biology of felines (who are true or "obligate" carnivores who MUST eat animal protein to not degenerate) in the direction of omnivores, as they've done with dogs. In the above paragraph, they call the dog an "opportunistic omnivore" who is "capable of surviving on a plant-based, vegetarian or vegan diet."

My sentiment: being "capable of surviving" is a terrible goal. Dogs are scavenging carnivores, in the Order Carnivora. They are in the same family as their cousins, gray wolves. As scavenging carnivores, dogs have no biologic requirement for carbohydrates, but they will eat whatever they must to survive, including filling up on plant material.

Historically, dogs have consumed a lot of human food waste, including enough corn, wheat, and rice foodstuffs to upregulate their amylase production (the digestive enzyme needed to break down starch) over time. Even though dogs (and cats) can consume and digest carbohydrates (hence the "opportunistic omnivore" label), they still haven't evolved to require them, nutritionally.

While it's true dogs will consume carbs to survive (or eat kibble containing 100% plant matter to sustain life), it's always their last choice. There's a substantial difference between surviving and thriving, based on what food is available (or fed).

There is compelling research demonstrating that when given a choice of macronutrients (fat, protein or carbohydrates coming from plant matter), dogs never choose carbohydrates first, they always leave them for last when there's nothing else to eat. In a nutshell, pets consuming conventional pet foods are omnivores by default and vegans by force — they must eat what food is offered, or not eat.

Dogs Have the Teeth, Jaws, and Digestion of a Carnivore

Animals' teeth are specifically created for the food they are born to eat. Your dog's teeth are designed to rip, shred and shear flesh off bone. Dog molars are pointed, not flat. Humans, who are true omnivores, have molars that are large and flat because they're designed to grind up plant matter. If you look at the teeth of other omnivores and herbivores, you'll see big, wide, and flat molars designed to chew plant matter.

Your dog has no flat molars because nature didn't intend for him to eat much in the way of plant matter. He also has powerful jaw and neck muscles that aid in pulling down and consuming prey.

The jaws open very wide to accommodate whole chunks of meat and bone and move only up and down (not side to side), because they're designed for crushing. In contrast, omnivores and herbivores have jaws that permit the lateral (side-to-side) motion necessary for grinding plant material.

Plant matter and vegetables need more time to break down in the gastrointestinal (GI) tract, which requires a different, more complex digestive design than your dog's body possesses. Biologically vegan animals, like cows, have a four-chambered stomach for this reason. This is also why vegetarian animals tend to masticate or chew their food over and over and over.

The term "wolf it down" refers to the tendency of canines to tear chunks of meat off prey and get them into their bellies as quickly as possible. Carnivores don't engage in much repetitive chewing.

Bottom line: While there are some genetic differences that have evolved between wolves and today's domestic dogs, it's not an argument for feeding solely plant-based diets to scavenging carnivores.

Forcing Carnivores to Be Vegans Is Unethical

The main thrust of the PetfoodIndustry.com article, which is written for manufacturers and others involved in the ultraprocessed pet food market, is captured in this statement:

"Based simply on the nutrient requirements of dogs and the composition of most plant sources for ingredients, one can determine likely shortcomings."

Indeed, plant-based diets for dogs have no shortage of nutritional shortcomings, which means the challenge for industry formulators and manufacturers is to figure out how to backfill the significant nutritional deficits of not only the base diets, but also those that occur during processing involving high heat and extrusion.

While I applaud those in the processed pet food industry who recognize the need for environmental stewardship and quality control with ingredient choices, it's important as scientists, doctors, and pet parents involved in the care and feeding of animal companions that we recognize we have an ethical responsibility to nourish them in a way that best resonates with their physiology.

According to the PetfoodIndustry.com article, "The interest by vegetarian and vegan pet owners wanting to explore feeding their dogs a plant-based diet will continue to grow." However, I believe it's not our place, as stewards of the earth and its inhabitants, to impose our personal dietary choices on other species, especially animals that would never innately choose to consume ultraprocessed vegan pellets as their sole food source.

As a wildlife biologist, wellness veterinarian and vegetarian, I understand how critically important it is that animal lovers recognize the unethical and damaging environmental effects of factory farming, conventional farming practices, and the almost 20 billion pounds of toxic glyphosate sprayed on food crops over the last 50 years.

The solution to these problems isn't singular or linear, and certainly won't be solved by feeding rejected agri-business plant byproducts to carnivores, in the form of vegan pet foods.

I understand the "whys" of this moral dilemma, but it's equally important to me, a doctor passionate about species-appropriate nutrition and longevity, that people do not assume veganism is healthy for all species.

Some animals have been eating solely plant matter for millennia, including rabbits, sheep, cows, and horses. Dogs and cats have not; their physiology and metabolism have not evolved to thrive solely on plants, much less ultraprocessed feed grade, genetically modified (and glyphosate-laden), high starch, heat-treated pellets (in essence, vegan fast food).

Understanding what constitutes biologically appropriate nutrition for the species you're caring for is a key first step in nourishing any pet in a way that respects their physiology. By feeding animals according to their physiology we reduce metabolic and immunologic stress. Step two involves choosing ethically sourced, sustainable/regenerative and nontoxic ingredients that fit within the framework of species-appropriate food.

Dogs evolved eating very high moisture diets containing large amounts of clean, unheated fat and animal protein, with adequate roughage (fiber from low glycemic plant material) and low/no refined starch.

Protein from plants isn't the same as protein from animal meat, and the dilated cardiomyopathy (DCM) crisis in carnivorous pets has proven this. While it's a fact that dogs are not wolves, they haven't evolved into vegans in the last 200 years, either.

When my unhealthy vegan dog patients have been offered the option of eating nutritionally complete fresh meat-based diets or vegan diets, they never choose vegan food. The problem is pets are rarely given the option to choose. We make them vegan; they don't choose to be vegan (highlighting more ethical issues). This moral issue has caused some countries to declare making pets vegan illegal.

Forcing dogs and cats to eat an entirely carbohydrate-based diet may seem like an ecologically responsible thing to do, but it's important to recognize that it comes at a potential cost to their health span and overall wellbeing down the road.

Unless you're preparing your vegan dog food at home with organic ingredients (including the 20+ synthetic nutrients that must be added in to avoid significant nutritional deficiencies), you should be very concerned about commercial farming chemical contaminants.

Because cancer-causing/organ-damaging mycotoxins and microbiome-disrupting herbicides are routinely found on conventionally grown crops in high amounts, they are also found in non-organic vegan pet foods.

Additionally, most commercial vegan pet foods on the market aren't made with ingredients approved for human consumption, just like all the other top selling, poor quality "feed-grade" pet foods on the market.

Animal feed products don't undergo stringent safety requirements, and while enthusiasts may think vegan pet foods have less contaminants because they're devoid of the factory-farmed leftovers the most popular kibble manufacturers use, the high levels of plant-based chemical residues found in conventional vegan diets may be far worse.

To my knowledge, there isn't a single commercial vegan kibble that has USDA organic status, is made with human grade ingredients, and is third party tested as being "clean." I'm sure those diets are in the pipeline, but there are other concerns about ultraprocessed vegan diets that are equally concerning.

Nutrition From Real Food, or Powders?

Plant-based ingredients are turned into dog food via extensive processing. In a nutshell, the transformation involves a lot of food refining and very long lists of synthetic nutrients and vegan protein isolates (such as pea protein) that must be added to plant-based ultraprocessed foods to meet minimum canine nutrient requirements.

I'll use a relatively recent entry into the meat-free kibble market, a product called Wild Earth Complete Protein Formula, to demonstrate the problems with some of the main ingredients in vegan pet foods:

Dried Yeast, Chickpeas, Peas, Oats, Pea Protein, Potato Protein, Canola Oil (preserved with mixed tocopherols), Sweet Potato, Flaxseed Meal, Sunflower Oil (preserved with mixed tocopherols), Dicalcium Phosphate, Calcium Carbonate, Natural Flavor, Marine Microalgae, Choline Chloride, Taurine, Dried Aspergillus oryzae Fermentation Product, Inulin (from chicory root), Potassium Chloride, Zinc Proteinate, Iron Proteinate, Fructooligosaccharides, Tocopherols (preservative), Salt, L-Carnitine, Vitamin E Supplement, Blueberries, Cranberries, Pumpkin, Spinach, Wheat Germ, Vitamin A Supplement, Copper Proteinate, Manganese Proteinate, Sodium Selenite, d-Calcium Pantothenate, Riboflavin Supplement, Thiamine Mononitrate, Vitamin B12 Supplement, Pyroxidine Hydrocholoride, Vitamin D2 Supplement, Calcium Iodate, Folic Acid, Rosemary Extract

Dried yeast is the primary ingredient. Did you know many vegan blogs encourage vegans to watch their yeast intake, and for good reason?

• Yeast contains a substantial amount of tyramine, a compound derived from the amino acid tyrosine. People who ingest large amounts of yeast can develop headaches and migraines because tyramine acts on the central nervous system, releasing various hormones that can lead to increased blood pressure.
• Over time, yeast consumption has been shown to trigger inflammatory bowel disease (IBD) in lab animals, and is associated with making autoimmune problems worse in people.
• Nutritional yeast is very high in glutamic acid, which ultimately becomes glutamate, an excitotoxin that can interfere with normal brain function by overstimulating neuron receptors in the hypothalamus. People who are sensitive to monosodium glutamate (MSG) know this and avoid eating foods containing large amounts of yeast.
• Yeast can contain high amounts of purines. Dogs' sensitive to purines or prone to urate stones or dogs with liver shunts should not consume an abundance of purine-rich foods.

Chickpeas contain lectins, "anti-nutrients" naturally found in legumes that reduce the absorption of vitamins and minerals and can cause GI inflammation.

The inclusion of pea protein and other vegan protein isolates or concentrates is the only way to get the percentage of protein high enough to meet minimum nutritional requirements. Legume and soy protein powders can contain high amounts of anti-nutrients and potentially damaging compounds including phytates, trypsin inhibitors, saponins and phytoestrogens that negatively impact the body in many ways, especially if fed repeatedly.

Canola oil is marketed by many vegan pet food companies as a source of omega-3 and omega-6 fatty acids, which is maddening to me. Canola oil is loaded with pro-inflammatory omega-6 fatty acids. In lab animals it's been shown to impair memory and create inflammation, even in the brain. There aren't any of the memory-enhancing, organ and skin supporting long chain omega-3s in canola oil.

Substantial amounts of DHA and EPA are required for well-being, but these delicate essential fats primarily come from sustainably sourced marine oils. Dogs can't convert plant omega-3s (alpha linolenic acid) to the DHA and EPA they need for brain, immune, cell and skin health.

Flaxseed meal is also marketed as an abundant source of omega-3s, but like canola oil, it isn't converted to EPA and DHA efficiently in pets. Flaxseed meal supplies fiber and alpha linolenic acid, but none of the missing EPA or DHA dogs require.

Sunflower oil adds still more pro-inflammatory omega-6s, probably genetically modified.

Marine microalgae can provide trace amounts of DHA and EPA, but because it's so expensive, it's added in insufficient amounts that don't serve dogs at all — it simply allows the company to market the product as supplying DHA (note DHA and EPA levels are not provided). Watch my Facebook Live on why microalgae powder can't provide adequate EPA and DHA for pets.

Choline and taurine must be added because there's simply not enough coming from real, whole foods in vegan pet food formulas.

Natural flavor is the deceptive ingredient that's added to vegan pet foods to entice pets to eat it. Laboratory-made palatants (including cadaverine and putrescine) trick dogs' noses into thinking the food contains meat.

It synthetically camouflages the smell of unenticing plant-based ingredients enough to lure pets into eating the food. Tricking a dog into eating food they would never naturally eat is also an ethical issue, in my opinion. More concerning is when you call the company and ask specifically what this ingredient is, they won't tell you.

Most importantly, there's an excessively long list of synthetic vitamins and minerals that are also be added because dogs must consume meat to obtain key nutrients that aren't present in vegan diets. The plant-based ingredients in vegan ultraprocessed diets provide only a handful of necessary nutrients, leaving the diet grossly deficient in a multitude of key nutrients that must be added in large amounts.

Most vitamins and minerals in commercial vegan pet foods don't come from biologically appropriate, real whole foods as nature intended, but from a bag, in powder form.

The list of synthetic, lab-made nutrients in vegan pet foods is extensive and must be added to make food pass minimum nutrient requirements set forth by AAFCO/FEDIAF, or the food would be grossly nutrient deficient, akin to any other highly refined, high glycemic carb-based snack (think corn chips).

The list of added synthetics includes the highly questionable sodium selenite, along with zinc, iron, vitamin E, copper, potassium, vitamin A, manganese, d-calcium pantothenate (B5), riboflavin, thiamine, vitamin B12, calcium iodate (iodine comes from ocean sources, this food includes the synthetic option) and vitamin D2 (not D3), pyridoxine (B6), l-carnitine.

This example of a vegan pet food label contains over 20 synthetic nutrients, supplying the bulk of the necessary vitamins and minerals required to avoid deficiencies from non-food sources. Vegan fed dogs must rely on laboratory-engineered nutrient powders mixed with fat and starch (sugar), to sustain life.

Nutritionists can check all the boxes on a pet food formulation spreadsheet to meet minimum nutrient requirements by supplementing with dozens of man-made nutrients so that vegan ultraprocessed pet foods can be labeled "nutritionally complete and balanced," but that doesn't mean we're creating long-term health by feeding these diets. It means we're conducting mass nutrition experiments on family pets.

There's never been any long-term studies evaluating the safety or efficacy of feeding ultraprocessed vegan diets to facultative carnivores. Your dog is the experiment. And while the most common short-sighted response is, "MY DOG IS THRIVING ON VEGAN KIBBLE," those of us who have seen the nutritional consequences of feeding species-inappropriate foods over time have a long list of real-life experiences that tell a different story.

A human food example is a popular vegan drink that is basically the same concept: everything you need in an "all in one" meal. Except it's not real food, it's a synthetic liquid supplement drink. Okay to consume now and then? Sure. A wise choice as a sole food source for the rest of your life? Probably not.

Is Vegan Fast Food Healthier?

Vegan ultraprocessed pet food is highly processed, just like other types of dry pet food. This adds another layer of insult, immunologically, when the conventionally farmed, previously heat-processed corn, potatoes, wheat, rice, and legumes that constitute the base of most commercial vegan pet foods goes through additional multiple high-heat processing steps to create kibble and canned food (what food scientists identify as creating " ultraprocessed" foods — the foods human nutritionists say to avoid).

When carbs are high heat processed into vegan fast-food (aka kibble), chemical reactions occur in the food that can't be un-done and create mayhem in the body once consumed.

The Maillard Reaction produces acrylamides during the extrusion and canning process and leads to the loss of essential amino acids and the formation of advanced glycation end products (AGEs) that negatively affect every cell of your pet's body and create mutagenic changes that damage DNA.

It's terribly deceptive to convince pet parents that they're creating health and well-being in their companion animals by feeding them feed ultraprocessed commercial vegan diets. The reality is that feeding a lifetime of high heat processed, industrially produced food pellets results in massive consumption of AGEs, and massive inflammation in the body (which sets the stage for many chronic degenerative diseases):

What Happens When We Pretend Carnivores Are Vegans

First, the carbohydrates that are a central feature of plant-based diets, including grains, potatoes, and legumes, displace the quality animal protein necessary for a dog's (or cat's) healthy body and organ function. Amino acid deficiencies have been implicated in a wide range of degenerative diseases, including nutritional cardiomyopathies.

Feeding biologically inappropriate diets results in metabolic stress, which eventually creates disease. Determining the biologic appropriateness of foods for dogs and cats means calculating the amount of unnecessary starch (sugar) in the diet. You can use this carb calculator to determine the digestible net carbs in your dog's current diet.

Dogs and cats should consume less than 20% carbs, with many experts suggesting the longest-lived dogs consumed less than 10%, on a caloric basis. Most vegan pet foods range from 50-85% starch, meaning a lifetime of excessive insulin secretion.

One of the most important things we can do to increase longevity and decrease disease potential in pets (including the risk of diabetes, obesity, and cancer) is keep their insulin levels low. It's impossible to keep insulin levels low when feeding solely a high starch diet.

Feeding your dog as a vegan means he'll inevitably have more inflammation and insulin release than dogs fed a biologically appropriate (low starch) diet.

Exactly how these health stressors impact your dog's body depends on how resilient he is (factoring in variables such as genetic predisposition, stress level, exercise, and environmental chemical load). But here's where common-sense reins: you can't feed inappropriate foods to pets and expect an appropriate health outcome.

Good vs. Bad Carbs (Phytonutrients vs. Sugar)

Dogs have co-evolved with humans for thousands of years, foraging on the same foods that humans eat, including meat, organs, and some plant material. This doesn't mean dogs evolved into cows along the way, nor have they evolved to eat kibble in the last 50 years, it means they acquired the ability to digest some plant material and their bodies benefitted from the nutritive substances in the limited amount of plant material they ate.

Research confirms that dogs benefit from low glycemic roughage from plant matter for health-enhancing phytonutrients, polyphenols, antioxidants and prebiotic fibers that don't come from meat, bones or organs.

And this is where the confusion begins; there are many plant compounds pets can benefit from, and there are many damaging substances in plants that can create disease. There are science-backed reasons to feed a small amount of "good carbs" to pets, I write about them here regularly. Unfortunately, commercial pet foods, including vegan diets, utilize the inexpensive, high glycemic "bad carbs" for the foundation of their products.

There's a monumental difference between the high glycemic refined starches used in commercial pet foods and the antioxidant-rich, polyphenol-rich phytonutrients coming from small amounts of low glycemic, fresh plants that both dogs and cats have been documented to consume in the wild. To make it simple, there's no comparing 2% fresh cilantro to 40% corn starch in a diet, yet both are "plant-based" ingredients.

Dogs are not "hypercarnivores" like snakes, who will die before eating an omnivorous, pelleted diet. Pets have consumed commercial pet foods (containing large amounts of refined, high glycemic plant material) for decades without worldwide, massive die-offs from starvation.

However, science is beginning to unravel how high starch ultraprocessed diets have negatively impacted overall canine health and longevity, and once I began delving into the research, I was compelled to track my findings and write The Forever Dog book. We know both dogs and cats can consume plant material without dying, the question is how much is too much, and in what form.

Research is clear that denying pets the beneficial parts of medicinal plants is detrimental; study after study demonstrates clear health improvements when specific polyphenol and antioxidant-rich herbs and superfoods are incorporated into a pet's diet. These critical longevity biomolecules are only found in whole, unrefined plants.

Studies also clearly demonstrate that denying dogs and cats all sources of fresh plant roughage by never offering prebiotic-rich, fibrous veggies results in a less healthy gut microbiome; "prey model" diets (with no phytonutrients from plants) aren't healthy, long term.

Nature Knows Best: Mimic Ancestral Macronutrients

Many research papers have demonstrated that pets benefit from a small amount of unrefined plant material in the form of high fiber veggies and fruits for their irreplaceable health and wellness benefits. Do the proportions of vegetable roughage need to be in balance with other macronutrients that support a biologically correct diet for these species? Yes. About 2-12% for cats, and less than 10% for dogs, according to self-selection macronutrient studies.

We interviewed the owners of the oldest dogs in the world, as the foundation of The Forever Dog book. Every exceptionally long-lived dog we found consumed some fresh foods, and they all ate meat-based diets.

Historically, however, there is one dog that is famous in the vegan dog food space: Bramble, a 25-year-old female Border Collie from the U.K. It's important to note the details of Bramble's long life, as I believe they are pivotal as to why this outlier cannot be compared to the majority of vegan dogs eating commercial vegan diets.

First, Bramble was not raised eating a vegan diet, but was later weaned onto a homemade, meticulously planned homemade, organic and highly diverse plant-based diet. She only ate one freshly prepared meal a day and no two meals were the same.

Bramble's owner didn't feed her ultraprocessed dog food, the kind being promoted by current vegan pet food companies. Instead, she fed her dog garden-fresh real food, plus rice and legumes. She paid attention to every dietary detail, including instituting soil amendments for the nutritional deficiencies found in her garden plot.

There were a host of other important details that most pet owners would struggle to imitate, including the exceptional amount of exercise (at least two hours a day) Bramble received via daily swimming sessions.

Polyphenols Are Healthy, Sugar Is Unhealthy

All the owners of the oldest dogs in the world that we interviewed fed appropriate amounts of unprocessed plant material in the form of fresh herbs, medicinal mushrooms, prebiotic-rich veggies, and antioxidant-rich fruits, and none of them incorporated large amounts of high glycemic starch into their dogs' meals.

The "veggie debate" comes down to common sense: feed small amounts of fresh produce from your fridge, not large amounts of high starch flours and sugar from the pantry.

In closing, I am an advocate of mimicking an animal's ancestral diet to maximize health span, happiness, and lifespan. This does not include vegan kibble or canned food. I believe our job as guardians is to choose to feed our animal companions wisely, with reverence and respect of their innate biology.

If you believe all your pets should be vegan, consider choosing animal companions that are innately vegan (i.e., rabbits, tortoises, horses, etc.). It's presumptuous and physiologically insensitive to choose obligate or scavenging carnivores as pets, and then demand they adapt to an unnatural and metabolically stressful feeding regimen.

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