Over the last forty years or so many Americans have, for perfectly valid reasons, made the decision to remove meat and dairy products from their diets. Whether they determine to become a vegan or a vegetarian, most feel their decision has improved their physical and spiritual well-being.

Many of these people also own one or more dogs. Because of their personal view and their own satisfactory dietary experiences, a substantial number then make the decision to adjust their dog's diet so that it is comprised exclusively from plant sources.

But is this decision a good one, from their pet's perspective?

Humans are omnivores. We are provided with saliva that contains various enzymes to predigest the starches in our diet, specific teeth to grind and breakdown the plant fibers we eat and a digestive tract of medium length. In addition, our jaws work in a manner that allows them to move not only in an up and down direction, but also from side to side, so we can easily eat foods derived from both plant and animal origins.

Dogs, on the other hand, are carnivorous. Unlike us, the jaws of dogs can only move up and down. Canine teeth are pointy and sharp, having evolved for tearing animal tissue, as opposed to the grinding of plant matter. Canine's saliva does not contain enzymes for breaking down grainy foods and they have a digestive tract that is short, for easy digestion of animal proteins and fats.

Besides these basic physiological differences between dogs and humans, there are a number of other concerns the dog owner should be aware of if considering placing their pet on a vegetarian diet. We'll touch on just a few of them here:

• If the owner's concern is to ensure that their dog will not suffer from high cholesterol or heart disease as do humans whose diets are high in meat intake, they should be aware that dogs do not suffer from coronary disease or cholesterol problems at anywhere near the incidence humans do. So cutting out meat and dairy products from the dog's diet may not provide any benefit.

• Dogs require a high amount of proteins, which are needed to support proper organ growth. Proteins are comprised of different amino acids. The best source of the required proteins is from animal sources. While there do exist some plant sources such as soy that contain high protein levels, the amino acids within soy are not as well-balanced as those derived from animals. Specifically, dogs require taurine and l-carnitine found in meat products. While one can add taurine and l-carnitine to a dog's diets, this raises another concern. Animal sources hold more protein, gram for gram, than do starches, grains or vegetables. So in order for the dog to get the required amount of taurine and l-carnitine, they will have to ingest a much greater quantity of food daily, which can lead to obesity and other health problems.

• Another essential nutrient required by dogs for good health is vitamin B12, which is not found in most plants.

While theoretically a dog owner can supplement his pet's diet with nutrients to overcome these dietary deficiencies, it can be expensive to do so. In addition, it is very difficult to monitor the amounts and the balance between the nutrients when they are inserted into an animal's diet not through natural foods, but with supplementation.

The bottom line is that dog owners should carefully consider all issues before putting their pets on a purely non-animal based diet. They should first research the matter and have a consultation with their veterinarian. Then, if they do make the decision to do so, they should strictly monitor the dog's health on a consistent basis and should any problems be observed, revisit the veterinarian.