With the interest in whole and natural foods for people, there has been an increase in popularity of raw diets for pets.* Advocates of raw diets argue that raw diets are better for cats and dogs. Reviewing these arguments shows they are based on three basic tenets: 1) cats and dogs are carnivores and evolved eating raw meats so should be fed a raw diet, 2) cooking foods alters their nutrients, making them less available, and destroys important enzymes used in digestion, 3) raw diets are beneficial for pets’ coats, immune function, allergies, and teeth.
What is the truth about raw diets?
Tenet #1: Cats and dogs are carnivores and evolved eating raw meats so should be fed a raw diet.
THE TRUTH: Not only are cats and dogs not both strictly carnivores, but the raw meat they eat in the wild is different than the meat in raw diets fed at home. Cats and dogs belong to the same order Carnivora, but while cats are obligate carnivores (they must have some meat in their diets), dogs are not. In the wild, cats’ and dogs’ diets do not consist solely of meat (they get carbohydrates from stomach contents, etc.), and the meat they eat is generally freshly killed with less likelihood of bacterial contamination. Bacterial contamination of raw food diets is a major concern in veterinary and human medicine. Finally, that cats and dogs evolved on a raw diet does not mean that a raw diet is superior to other diets. To “evolve” on a particular diet, a cat or dog only needs to live long enough to produce viable offspring. For cats and small breed dogs who can have offspring well under a year of age, they wouldn’t have to live very long to “evolve” on a raw diet. In addition to living longer (feral dogs rarely live more than six years, and feral cats’ life span is two to three years), selective breeding means that our domesticated dogs and cats are far removed from their ancestors.
Tenet #2: Cooking foods alters their nutrients, makes them less available, and destroys important enzymes used in digestion.
THE TRUTH: Cooking foods does alter nutrients and destroys enzymes. One often-cited study in support of raw diets is “Pottinger’s Cats,” a study in which cats fed a cooked diet failed to thrive. Taurine, an essential amino acid for cats, is sensitive to heat. The cats in this study suffered classic signs of taurine deficiency. This has been used as an argument for the power of raw food (rather than to emphasize taurine needs of cats). Thiamine is a vitamin that is also heat-sensitive. Taurine, thiamine, and other vitamins affected by heat processing are supplemented in cooked diets. Other nutrients’ bioavailability is actually enhanced by cooking. With cooked commercial diets, unlike with raw diets, the average digestibilities have been published so we know what is digestible/bioavailable. Finally, the enzymes contained in raw foods are not used in digestion. With the exception of pancreatic enzyme supplements for dogs with exocrine pancreatic insufficiency, enzymes are made in the body for digestion, and are not obtained from the diet.
Tenet #3: Raw diets are beneficial for pets’ coats, immune function, allergies, and teeth.
THE TRUTH: There is no scientific research supporting these claims, which are either patently false or can be attributed to other qualities of raw diets rather than them being uncooked.
Coat quality: Raw diets tend to be higher in fat—this (rather than the diet being raw) may account for anecdotal reports of improved coat quality.
Immune function: Again, there is no scientific evidence to support an improvement in immune function with raw diets. Even many proponents of raw diets do not recommend them for pets with compromised immunity.
Allergies: Since food allergies are most commonly protein-based, improvement in allergies on a raw diet is likely due to the elimination of the allergen (for instance, feeding a protein source that cat or dog is not allergic to), rather than the diet being uncooked. Similar results would likely be obtained by cooking the same diet.
Teeth: Research actually indicates that raw or natural diets are not beneficial, and can be harmful for pets’ teeth. The argument that raw diets improve pets’ teeth is based on the idea that chewing on fibrous meat tissue and/or bones will clean pets’ teeth. Published studies on feral cats in Australia and English Foxhounds that were fed raw carcasses found both groups had tartar, fractured teeth, and periodontal disease, despite these “beneficial” raw diets. Veterinary dentists and even the Food and Drug Administration do not recommend pets be given bones due to the general health risks as well as the risk of fractured teeth.
Overall, the purported benefits of raw diets are either not supported by scientific research or are not due to the diet being raw per se, and are outweighed by the risks of feeding raw diets (see The Raw Truth, Part 2, coming soon). Because of these risks, the AVMA (American Veterinary Medical Association) and AAHA (American Animal Hospital Association) have both come out with statements against feeding raw diets to cats and dogs.
*Note that whole and natural foods can be fed to cats and dogs in a cooked version, and cooking foods is one of our recommendations to deal with some of the health concerns in feeding a pet a raw diet. See The Raw Truth, Part 2, coming soon.