Food for Thought Friday: Low-Carb Logical Fallacies

Time for another round of things that make us go hmmm.

Last time in Food for Thought Friday, I addressed the issue of ketosis, carbs, and alcohol. I’m pleasantly surprised at the number of page hits it’s gotten. Here, I thought it was kind of a throwaway post, a quick one-off just to get something up on the blog before people forget I exist. But it seems the topic struck a chord, or maybe people just like reading about ketosis & alcohol. (And who can blame them? Either together or separately, they’re great topics!)

Since I pointed out the problems with the keto-haters suggesting ketones are “dangerous” or “unnatural” because the body stops producing elevated levels of them as soon as it has any appreciable amount of glucose in the bloodstream, today I thought I’d point out a logical fallacy that low-carbers are prone to using—myself included. It goes a little something like this:

If dietary fat were fattening, they would use lard, tallow, and butter to fatten cows in feedlots, but they don’t. They use grain. Therefore, grains are fattening. (And we extrapolate this to humans.)

Now, believe me, I agree that this is true. But that doesn’t mean it’s an argument that works well in our favor—especially when a counter-argument we might get from vegans, vegetarians, and what Dr. Richard Feinman calls “the lipophobes” goes something like this:

Cows maintain optimal health by eating nothing but grass. Therefore, animal fats and proteins are unnecessary for a healthy diet. (And they extrapolate this to humans.)

You see the problem here, right?

I’m guilty of using the “they use grains to fatten cattle” logic, myself, but that was in the past. Now that I’ve realized counterarguments are so easy to think of—even if they’re incorrect—I try to steer clear. (No pun intended, hehheh.)

It’s a logical fallacy to say that what works for one animal species will work for some other animal species. This is what got us into trouble back in the day, when they fed cholesterol to rabbits—herbivores. So yeah, of course that led to problems in these bunnies’ blood vessels. They were being fed something that is not an appreciable part of their natural, species-appropriate diet.

And when we feed steers and dairy cows foods that aren’t part of their natural diet, of course biological problems ensue. And even though I agree that grains are fattening for humans (at least, those who are insulin resistant and have a low carbohydrate tolerance, since we have plenty of examples of population groups who do not become obese via grain consumption), we have to base that argument in human physiology, rather than on that of ruminant animals.

Just because grains fatten cows doesn’t automatically mean they’ll fatten humans. And just because cows and sheep thrive on grasses and greens, exclusively, doesn’t automatically mean that humans will.

Why? A little something called the digestive tract. Ruminants and humans have digestive tracts that are worlds apart. We are literally different animals, and there’s no reason to assume that we can thrive on the same type of diet. (But I guess the only people making this claim would be anyone who believes humans can thrive on raw green plant matter and nothing else. And not even the raw foodists are saying that, ‘cuz some of them eat raw nuts & seeds, don’t they?) 

I won’t bore you with a long anatomy lesson, but the bottom line is, ruminant animals have multi-chambered “stomachs,” or pouches. One of these is called the rumen, hence the term “ruminant.” (Also, hence the verb “ruminate,” which means to mull something over for a while, turning and churning it this way and that, just like happens to food inside the rumen.)

A rumen is a gigantic fermentation vat. It’s like a sauerkraut crock right there inside cows, sheep, goats, and other ruminants. The chambers of these digestive tracts are loaded with bacteria. They are loaded with certain species of bacteria that human GI tracts do not harbor, and these bacteria help cows convert the cellulose of plant material (carbohydrate) into protein, which you might be familiar with in the form of delicious things such as brisket and filet mignon.

And as long as I’m on the subject, I’ll introduce another logical fallacy I’ve used in the past: cows produce plenty of poop without any “added fiber” in the form of whole grains or flaxseeds. Yes, green vegetation is loaded with indigestible plant fiber, and ruminants eat a ton of this green vegetation, but that just goes to show that feces can be produced just fine in the absence of high-fiber cereal, bran muffins, or Metamucil and psyllium husk. (In fact, if you ask a farmer raising his steers exclusively on grass, he/she will confirm for you that they produce plenty of poop.)

Way back in the digestion series, I said, “Obligate carnivores, like lions and tigers, don’t spend their days on the savannah chomping down on endless piles of kale, broccoli, or bran muffins, and they seem to defecate pretty well without pharmaceutical intervention. I’m not suggesting the anatomy and physiology of these big cats are the same as humans, so therefore we don’t need any fiber, either. I’m simply pointing out that somewhere in nature there exists a mechanism for allowing healthy animals to excrete feces without the need for copious amounts of plant fiber.” Obviously, plenty of animals excrete dung without isolated fiber from grains, seeds, or copious amounts of green vegetation. (Or almost any vegetation, for that matter. In fact, I’ve been giving a lot of thought to this as it regards humans, so be on the lookout for a couple of posts on whether vegetables are "required" for people.)

To recap: in the animal kingdom, we have species that thrive (and poop) on plant-only diets. And we have other species that thrive (and poop) on animal-only diets. However, in the interest of intellectual honesty here, let me point out that in the course of eating so much vegetation, we have to assume ruminants are also consuming a lot of insects, worms, larvae, and whatever other tiny critters might be lurking in all that grass. But we can hardly call them “carnivores.” And even obligate carnivores and “mostly” carnivores still occasionally consume plants, but we wouldn’t call lions and tigers “herbivores.”)

So yes, we have widely varying diets that work well for the widely varying anatomy and physiology of different animal species. But the reason those widely varying diets work is because the species have widely varying anatomies & physiologies. To suggest that grains fatten humans because they have been shown to fatten cows is a leap of logic as shaky as suggesting that raw grass and nothing but raw grass can keep humans healthy because it keeps cows healthy. (This is just as unhelpful as postulating that all humans can thrive on high starch diets because the Kitavans do, or that we can all thrive on high meat and fat diets, because Arctic peoples do.)

Again, I’m not saying grains don’t or can’t fatten humans. I’m saying only that if we use the grains/feedlot/fattening angle, we should be prepared to back it up with something based on human anatomy, digestion, and endocrinology, rather than the logical misstep of extrapolating from ruminant physiology to our own. We have the answers (at least, I think we do), but we strengthen our case by knowing why they’re the answers.

Remember: Amy Berger, M.S., NTP, is not a physician and Tuit Nutrition, LLC, is not a medical practice. The information contained on this site is not intended to diagnose, treat, cure, or prevent any medical condition.