kitchen table math, the sequel: dogs are omnivores

Monday, February 11, 2013

dogs are omnivores

Back to the vet's today for our third set of stitches and a really huge dog-cone attached via chest strap.

At the office I pussy-footed around the subject of: can a dog be a vegan? (I read The China Study two years ago, see below.)

"Do dogs need to eat meat?" I asked.

The vet, who tends to scoff a lot (I was hoping to forestall scoffing), gave me a look. "What do you mean, meat?" he said. "Do you mean raw meat?" He looked like he was fixing to scoff.

Raw meat, as I discovered yesterday, shows up frequently on websites devoted to dog nutrition. I haven't learned why as yet.

"Well," I said, "sure. Raw meat. Or cooked meat. Or just meat in general. Should I be giving Surfer real meat?"

"Dogs aren't obligate carnivores," he said.

What? Dogs aren't carnivores? (And what's obligate?)

I was gobsmacked.

An "obligate carnivore," it turns out, is a cat. A cat has to eat meat or it will die, hence the term "obligate." Cats are obliged to eat meat. Dogs are not obligate carnivores, and they are not obliged to eat meat. They just like to eat meat, same as people, but a dog can be a vegetarian. The vet actually used the word "vegetarian" himself, which is a lot better than me saying "vegetarian" and getting scoffed at. If I remember correctly, and I think I do, the vet actually said, "A dog can be a perfectly healthy vegetarian."

So today Surfer ate Amy's lentil soup, diced tomatoes, olive oil, and a boatload of fish oil. He was a pretty good sport about it, but I don't think he's going to be too thrilled when the cruciferous vegetables show up.

From The China Study:
...I decided to start an in-depth laboratory program that would investigate the role of nutrition, especially protein, in the development of cancer....I chose to do this research at a very basic science level, studying the biochemical details of cancer formation. It was important to understand not only whether but also how protein might promote cancer....

What we found was shocking. Low-protein diets inhibited the initiative of cancer by aflatoxin, regardless of how much of this carcinogen was administered to these animals. After cancer, initiation was completed, low-protein diets also dramatically blocked subsequent cancer growth. In other words, the cancer-producing effects of this highly carcinogenic chemical were rendered insignificant by a low-protein diet. In fact, dietary protein proved to be so powerful in its effect that we could turn on and turn off cancer growth simply by changing the level consumed.

Furthermore, the amounts of protein being fed were those that we humans routinely consume. We didn't use extraordinary levels, as is so often the case in carcinogen studies.

But that's not all. We found that not all proteins had this effect. What protein consistently and strongly promoted cancer? Casein, which makes up 87% of cow's milk protein, promoted all stages of the cancer process. What type of protein did not promote cancer, even at high levels of intake? The safe proteins were from plants, including wheat and soy.


But how much protein is too much or too little? Using rats, we investigated a range of 4-24% dietary protein....Foci did not develop with up to about 10% dietary protein. Beyond 10%, foci development increased dramatically with increases in dietary protein.


The most significant finding of this experiment was this: foci developed only when the animals met or exceeded the amount of dietary protein (12%) needed to satisfy their body growth rate. That is, when the animals met and surpassed their requirement for protein, disease onset began.

This finding may have considerable relevance for humans even though these were rat studies. I say this because the protein required for growth in young rats and humans as well as the protein required to maintain health for adult rats and humans is remarkably similar.

According to the recommended daily allowance (RDA) for protein consumption, we humans should be getting about 10% of our energy from protein. This is considerably more than the actual amount required....What do most of us routinely consume? Remarkably, it is considerably more than the recommended 10%. The average American consumes 15-16% protein....


[D]id it make any difference what type of protein was used in these experiments? For all of these experiments, we were using casein, which makes up 87% of cow's milk protein. So the next logical question was whether plant protein, tested in the same way, has the same effect on cancer promotiona s casein. The answer is an astonishing "NO." In these experiments, plant protein did not promote cancer growth, even at the higher levels of intake....Gluten, the protein of wheat, did not produce the same result as casein, even when fed at the same 20% level.

China-Cornell-Oxford Project 


Anonymous said...

A well thought out refutation to the China Study can be seen here:

Anonymous said...

Take a look at "Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live" by Marlene Zuk. She discusses the evolutionary changes in dogs triggered by domestication. Dogs were domesticated in part because their ancestors were wolves who could handle eating human thrown-away food, which was largely bread and the like. The book is a good read.

Catherine Johnson said...

oh-I'm interested to hear about Marlene Zuk. There's a new study (that I'm not sure how to evaluate) saying that dogs are **not** juvenile wolves. (The argument has to do with the shape of dog faces....which strikes me as possibly irrelevant .... but, as I say, I can't parse it.)

Nevertheless, if dogs are **not** juvenile wolves, then there must be a different mechanism for domestication, and that certainly could have to do with food.

On the other hand, if wolves are omnivores, too....

(Are wolves omnivores?)

Catherine Johnson said...

Wow --- this is very interesting.

As far as I can tell, wolves are carnivores. But dogs aren't.

I found this abstract from a dissertation on wolf diet that was written in Sweden:

Although the diverse diet confirmed the wolves’ nature as opportunistic predators, moose was the most common item in percent frequency of occurrence in summer (53.7%) and winter (68.5%), representing 88.9% and 95.7% of the mammalian biomass consumed in summer and winter, respectively. Other prey species like roe deer, beaver, badger, hare, small rodents and birds were regularly used during the year, with emphasis on the summer months. Within the studied period domestic animals only contributed marginally to the diet of wolves. Nevertheless, domestic animals were more frequently identified in summer than in winter with 1.3% and 0.1%, respectively. Moose was the preferred prey in summer (Manly’s Alpha = 0.68) and winter (Manly’s Alpha = 0.54). Food niche breadth was broader in summer (BA = 0.11) than in winter (BA = 0.04). This may be explained by the higher availability of smaller prey species like beaver, hare, small rodents and birds during the summer period.

I don't see any roots and berries on that list.

Catherine Johnson said...

It's funny because we have two dogs: Surfer, a mutt, and Abby, a Labrador.

Abby is a TOTAL omnivore. Total, obvious, natural: she will eat anything. She's practically a goat.

Surfer is much pickier.

I've been assuming (rightly or wrongly) that mutts are closer to wolves in terms of gene expression....I'm assuming that dogs start to 'revert back' to wolfiness after a few generations to breed naturally.

If that's true, then Surfer has become more 'wolfy' in his tastes.

This may be completely wrong, of course....

I did find some interesting research on wolves versus dogs, though, saying that although wolves and dogs are practically the same animal in terms of DNA, their gene expression is completely different.

It's that difference in gene expression, not in DNA, that makes dogs and wolves different.

Catherine Johnson said...

I'm looking at the paleofantasy book. For what it's worth, my view, based in the various reading I've done over the years, is that she's right: evolution can happen much, much more quickly than we've been led to believe.

At the same time, farming was introduced just 10,000 years ago .... and high-tech processed foods are around 100 years old (??)

In my own mind, I always assume that a lot of us are probably best off eating a pre-farm diet.

That may be completely wrong, of course --- and I also assume that a big part of the human population has adapted to grains. The trouble is that I don't think I can tell which cohort I'm in personally.

Hainish said...

"I'm assuming that dogs start to 'revert back' to wolfiness after a few generations to breed naturally."

This could only happen if dogs actually interbred with wolves. Otherwise, where would the wolfy parts of the genomes come from? They're still drawing from the doggy gene pool, just in ways that won't wind them awards for best in show.

"It's that difference in gene expression, not in DNA, that makes dogs and wolves different."

To nitpick: What you mean to say is that it isn't differences in protein-coding DNA. This restriction is important because gene expression differences *are* due to differences in DNA, but it is the regulatory regions of DNA upstream and/or downstream of the actual protein coding regions.

Hainish said...

Also, you should look up the paleo diet (no grains. legumes, or dairy), which is based on exactly the premise you mention.

K9Sasha said...

Here's an interesting discussion on whether or not dogs descended from wolves:

And another one on dogs and starches: