Reading about dog diets

I’ve been curious for a long time about how raw diets became so popular for dogs, since there’s a lot of misinformation about them. (Dogs can and do get food poisoning, for example.) When I started reading, it seemed like I found more and more people cited the same studies, studies that weren’t about dogs at all, like the Pottenger study on cats.

I went back to the original research on canine nutrition.

It’s mostly presented in the book Nutrition of the Dog by Clive McCay. It’s readily available used for fairly cheap if you do a search on ABEbooks.com (the website of the American Booksellers Exchange–great for finding used books). It was published in 1943 and is about how to maintain research dogs if you’re going to be doing research.

Dogs were used in much early medical research, on diabetes, rickets, and in early B-vitamin research. I had the good fortune at MIT to take biochemistry from Gene Brown who did the original research on B vitamins in the ’30s and he’d mentioned some of the research; it was mostly done by elimination diets. When I started doing working out diets for Elly, as a result of her inflammatory bowel disease, I kept hearing all the stuff about raw diets and was curious where it originated.

Lots of people will tell you that raw diets are a result of the study with cats where cats died if they were given cooked food. True. That’s because long cooking destroys taurine which is an essential nutrient for cats but not for dogs. And cats are obligate carnivores while dogs are omnivores. Dogs evolved from wolves as scavengers in village dumps, according to Coppinger, and I think his research on that makes a lot of sense. (McCay also talks about the role of dogs in scavenging and thus keeping villages healthy.) So dogs evolved from wolves as scavengers and part of that was eating cooked food, because we do.

I wanted to get more information on the original research on dog diets. I went back to Clive McCay and I read his book. He was maintaining populations of dogs for researchers and his interests seem to have been having healthy dogs for the researchers and not the dogs themselves. They bred the dogs so as to have a large controlled population. (John Gibbons, the developer of the heart-lung machine, was a family friend; he did his first surgeries on dogs, too. Dog research used to be a lot more common than it is now.)

McCay–like any good lab–wanted to keep his costs down, so he was mostly feeding stuff no one else wanted. One of his diets used tomato pomace, which is what’s left if you press tomatoes for juice. (I notice it’s also used in the Wellness food I feed.) He feed “meat scraps from the butcher” as well. And here’s the quotation: “Over a century ago, Magendie found that dogs could be kept alive for long periods upon fresh bones; but if the bones were boiled, the dogs died within a couple of months.” (p.26, third printing, 1946). He goes on to say “the cooking of meat for dogs is a waste of time from the point of view of nutrition.” (p. 26)

With regard to the tomato pomace, he says it “is a rich source of pectin, which regulates the water of the feces within limits and safeguards the dog from diarrhea and constipation under normal circumstances.” (p. 103). Here you have the reason why the diet rich in fruits and vegetables works so well for IBD.

(I also like McCay’s observation that “probably the greatest evil in over-feeding either men or animals is the deposition of excess body fat. It shortens the span of life.” (p. 21))

McCay notes that some foods are dangerous for dogs when fed raw. Corn and eggs both should be cooked. Carrots provide more useable vitamin A when cooked.

While McCay’s book is almost seventy years old, I’ve found the research in his book stands up well. He discusses calorie-limited diets. His proportions of various vitamins and minerals in the canine diet are still recommended. He talks extensively about how different diets affect the feces (dogs feed just meat and bones apparently defecate as little as once a week). He even addresses the needs of dogs (and humans) for adequate amounts of vitamin D. One thing I like is that his book predates the chemical approach to nutrition that is now so common; his recommendations for vitamin supplementation usually require adding a specific food to the diet, not a chemical powder.