Why Vegetarian and Vegan Diets are NOT Recommended for Dogs

I’ve written about vegetarian and vegan diets for dogs in a couple of past newsletters. First was in 2003 and then it was updated with additional information in 2014. I also wrote extensively about this topic in my book Raw and Natural Nutrition for Dogs. While opinions and theories change as new information becomes available, I will say that my opinion on this subject has NEVER changed. I say the same thing today that I said in past newsletters and in my book. Please do not EVER feed any dog a vegetarian or vegan diet! Dogs are not humans! They do not digest food the same way humans do and they have different nutrient requirements needed to maintain their good health.

Bramble, a Border Collie from the UK, is often used as an example of a dog that lived to be 25 years old on a vegan diet. What is oftentimes left out of her story is that Bramble was a farm dog that was able to run free daily. I can only imagine that Bramble loved the porridge her owner gave her, but she was also opportunistic and spent much of her free time foraging for small rodents and rabbits.

Dogs will certainly eat what we provide for them. They do not have a choice in what we choose to feed them and therefore are subjected to what we decide to feed them. Hunger itself will cause the opportunistic dogs to eat what we set before them. However, we need to understand and take a closer look at what dogs need to THRIVE, not just survive!

Humans are omnivores and have a medium length digestive tract. When we eat food, it spends a relatively short time in the stomach and the bulk the time in the intestines to complete the digestion process. Humans have enzymes in their saliva to help predigest starches. Our jaws move up and down and back and forth to chew plant material and help pulverize and prepare food for digestion.

Dogs are carnivores. As such, they have a much shorter and simpler digestive tract than we do. In the digestive process, the food dogs consume spends the greatest amount of time in the stomach. Dogs have more gastric juices than humans do because carnivores need these in greater amounts to digest bones, break down animal fats and kill bacteria. After the digested material leaves the stomach, it goes through the intestinal tract rather quickly. Because of the short digestive tract, dogs have little or no ability to ferment foods. Therefore, their digestive tract is not designed for handling large amounts of fiber (grains, starches, fruit and plant material).

Canine teeth are sharp and pointed for the purpose of hunting and ripping, tearing and chewing meat and bone. Dogs have a large mouth opening to swallow larger amounts of food than humans can. Their jaws only move up and down (never sideways) and are not designed to mash up or pulverize plant materials. Additionally, they have no enzymes in their saliva to assist in starch digestion.

Protein and Dogs

Animal protein sources contain several nutrients not found in vegetarian and vegan diets. One important nutrient is the amino acid taurine. Protein is essential to organ and skin integrity, growth, and a healthy immune system. Amino acids provide the building blocks for these components that are essential for life. Each of these amino acids is specialized, and all of them work together to keep the body healthy. In humans, nine amino acids are needed to make up a complete diet. In dogs, at least ten amino acids are needed, and quite possibly eleven. As carnivores, dogs require certain amino acids in different amounts and ratios than humans.

Taurine and L-Carnitine

Research on nutrition and the heart in canines has shown some interesting results. It has been proven that Taurine is essential to cats, but the emphasis on the need for Taurine in dogs has been neglected. New studies show that certain breeds are prone to dilated cardiomyopathy (DCM), such as Newfoundlands, and are oftentimes found to have a taurine deficiency. Studies on this are also being performed on Doberman Pinschers. Other breeds that are affected include Boxers, Cocker Spaniels, and Golden Retrievers. While scientists previously believed that dog foods high enough in sulfur containing amino acids (such as cystine and methionine, which can produce taurine) and proteins would allow canines to produce taurine, now believe this may not always be true:

http://www.ncbi.nlm.nih.gov/pubmed/16988121

Another amino acid needed in the dog’s diet is carnitine. This study shows that a carnitine deficiency can cause DCM (Dilated Cardiomyopathy) in dogs:

https://www.ncbi.nlm.nih.gov/pubmed/17085238

Note that the dogs used in these studies were fed a dry dog food. While only animal proteins contain taurine, certain preparation of animal proteins can deplete taurine in the diet:

“Animal muscle tissue, particularly marine, contained high taurine concentrations. Plant products contained either low or undetectable amounts of taurine. The amount of taurine that remained in a feed ingredient after cooking depended upon the method of food preparation. When an ingredient was constantly surrounded by water during the cooking process, such as in boiling or basting, more taurine was lost. Food preparation methods that minimized water loss, such as baking or frying, had higher rates of taurine retention.”

http://onlinelibrary.wiley.com/doi/10.1046/j.1439-0396.2003.00434.x/abstract

Dog food companies tend to add sulfur to their commercial diets because they know the high heats of cooking the small amount of animal protein in their formulas destroys the amino acids. However, while sulfur in the diet can assist dogs in making taurine, it appears to vary in the amount needed by breed and by size of the dog. To date, not enough research has been performed to understand how much taurine is needed for a processed diet heavily laden with carbohydrates. This leads to another problem with vegetarian and vegan diets.

Carbohydrates in the Dogs Diet

Carbohydrates are comprised of sugar and most are very high in fiber. The dog’s digestive tract is designed specifically to consume, utilize and digest animal protein and fat. As mentioned earlier, it is short and simple, and labors with diets high in fiber. Even though starches and grains are more easily digested when cooked, they still afford too much fiber for a canine to properly digest. Due to their struggle in processing high-fiber foods, it results in the production of gas and large, loose stools with very strong odor. Additionally, because dogs are unable to ferment fiber, this type of diet is very irritating to the small intestine and intestinal lining. As humans, we can have a tendency to project our dietary needs on to our pets. This is why it is so important to understand the nutritional needs of dogs and how their needs are different from ours. Not only is the high fiber, carbohydrate diet irritating to dogs, the abundance of sugar in carbohydrates causes obesity, body odor and red staining around the eyes, on the coat and feet. Sugar promotes both yeast growth and tooth decay in dogs. REMEMBER, dogs have NO way to break down starches in their mouth. Therefore, the food lodges in their teeth and can result in tooth decay and gum disease.

Minerals

Plant sources are also a poor source of minerals. Probably the most important mineral to consider is calcium. Plants, including grains, are a poor source of calcium. They are high in phosphorus, potassium and magnesium, but low in calcium and sodium. Furthermore, grains and many vegetables are high in phytates, which block the absorption of calcium, iron, zinc, iodine and magnesium. This fact was brought to the attention of the dog food companies in the early 80’s. However, rather than reduce the amount of grains and starches in their commercial products, they simply opted to add more calcium, zinc, magnesium and iron.

A vegetarian diet, and especially a vegan diet, needs added calcium, zinc, magnesium, iron and iodine to balance the diet. The problem with adding minerals to the diet is that adding too much or adding improper combinations can be just as dangerous as getting too little. Minerals need to be supplemented in specific amounts in order to balance with each other. Most important in the canine diet, is the calcium and phosphorus balance and the zinc and copper balance. Of all the nutrients we may supplement, balancing these minerals is of the utmost importance if you are feeding a diet that is low or devoid of these minerals. A home-prepared diet with meat, eggs and dairy provides the balance of all of the minerals, except calcium, in a form dogs can readily use. Adding raw meaty bones to the diet provides the needed calcium. Vegetarian and vegan, or plant-based diets, do not contain these needed minerals in a form that can be digested AND utilized by dogs.

Remember, the phytates found in most grains, many starches and vegetables could bind calcium, iron, magnesium and zinc. Oftentimes, diets high in these foods need more calcium than a diet high in animal-based food sources. Additionally, high fiber diets make iron absorption more difficult. Dogs utilize iron more efficiently from animal-based sources such as meat, eggs, yogurt and fish.

Vitamins

Another important area to address is vitamins and vitamin deficiencies. These include Vitamin A, B vitamins and Vitamin D.

The Vitamin A found in meat sources is called retinoid. The Vitamin A found in plant sources is called beta-carotene. Dogs, and especially cats, have a difficult time converting beta-carotene to a usable form of Vitamin A. Animal proteins provide this important vitamin in its ‘already converted’ state. Therefore, it is important to feed dogs a diet that contains animal proteins so they benefit from this important vitamin.

Vitamin A in either form requires fat to be absorbed in the intestines. Therefore, consuming a high-fiber diet can interfere with the uptake of this important vitamin.

https://www.dsm.com/markets/anh/en_US/Compendium/companion_animals/vitamin_A.html

The level of beta carotene fed dogs decreases very rapidly, compared to humans and other mammals. This is important to note, as the retinol form is usable when consumed by dogs, and they don’t process beta carotene to a usable form as effectively as rats or humans.

https://academic.oup.com/jn/article/130/7/1788/4686191

“These are called preformed vitamin A because they are in a form that your body readily uses.  Retinol is the most usable of the three forms and can be converted to both retinol and retinoic acid in the body.”

https://www.sharecare.com/health/vitamin-a/vitamin_a_beta_carotene

“Niacin [vitamin B3] deficiency is generally encountered when owners formulate their own diets for their pets and do not include meat as part of the ration. Be very careful when trying to convert a pet into a vegetarian. Riboflavin [vitamin B2] is found naturally in organ meats and dairy products. It is lowest in grains, vegetables, and fruits. The un-supplemented vegetarian pet is at extreme risk of developing a riboflavin deficiency. Dogs fed a diet deficient in vitamin B2 will have poor growth, eye abnormalities, weakness in rear limbs, and eventually heart failure.”

Vitamin D has been found to be lower in blood plasma in dogs fed a vegetarian diet. This is a great concern, especially for growing puppies. This is caused from using plant-sourced vitamin D (D2) and increased fiber intake, which blocks the uptake of this vitamin. Dogs need vitamin D3, NOT vitamin D2. D2 is plant sourced and dogs simply cannot absorb and utilize this type as efficiently. Dogs require D3, which is animal sourced. Dogs are unable to absorb vitamin D from the sun.

http://www.ncbi.nlm.nih.gov/pubmed/7843559

“In contrast, the skin of dogs and cats contains significantly lower quantities of 7-dehydrocholesterol than other species, and its photochemical conversion to cholecalciferol is quite inefficient; dogs and cats thus appear to rely on dietary intake of vitamin D more than do other animals.”

http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/vitamind.html

Also note, the research shows that Vitamin D2 (mostly plant based) has little effect on humans and an even poorer effect on dogs. Always use vitamin D3 as the supplement choice.

http://www.ncbi.nlm.nih.gov/pubmed/17023693

This link is full of research sources showing how much more effective vitamin D3 is for humans and other mammals:

http://www.vitamindwiki.com/tiki-index.php?page_id=2138

Summary

Most vets do not recommend feeding a vegetarian diet to dogs. I personally do not believe it is possible to feed a vegetarian or vegan diet to a dog and successfully supply all the nutrition that a dog needs.

A study of dogs in Europe that were fed a vegetarian diet showed the following results:

• Over half the dogs showed inadequate protein intake
• Calcium requirements were not met in 62% of the dog’s diets
• Phosphorus requirements were not met in roughly half the dogs
• 73% had an insufficient intake of sodium
• A high number of blood samples showed insufficient amounts of iron, copper, zinc and iodine, as well as vitamin D
• 56% of the dogs were not getting enough vitamin B12.
• Even the commercial vegetarian diets were found not to meet the nutritional needs of dogs.
• Even sources that support feeding vegetarian diets to dogs stress the complexity of supplying all the necessary nutrients and the dangers of leaving them out. The better sources recommend feeding eggs and dairy, even if meat is not fed.

Before anyone chooses to feed a vegetarian diet to their dog, they should have a thorough understanding of the dog’s nutritional requirements and know how they will meet their dog’s dietary needs feeding a vegetarian or vegan diet. This includes adding which vitamin and mineral supplements and in what amounts, should be given. Additionally, no dog should be fed a vegan diet, which is incapable of meeting his or her nutritional needs.

Lastly, it is important to look at the needs of the dogs, and cats, we choose to have in our lives. While we may have our own ethical or moral choices in what we eat, we are responsible for the care and wellbeing of our pets. It is certainly fine that you eat the vegetarian or vegan diet if you believe is right for you, but it is unfair to impose the same beliefs and diet onto your pets. Dogs and cats require animal proteins in their diet to meet their health needs. To make a conscious decision to feed carbohydrates to your dog, along with a myriad of supplements to try to make up the vitamin and mineral deficiencies of a meat-free diet is unhealthy for your pet. It is also selfish and unkind. The results of a vegetarian or vegan diet results in a higher risk of obesity, and leaves you with an unhealthy pet whose palate and nutritional requirements are not met. It is very important to separate our needs from our dog’s needs and provide them with the best nutrition, physical exercise and mental stimulation that is appropriate for them and not us!