February 22, 2010
How many times have we all heard this bunk myth repeated?
"Humans can't actually digest meat: it rots in the colon."
And its variant: "Meat takes 4-7 days to digest, because it has to rot in your stomach first."
(Some variations on this myth claim it takes up to two months!)
Like most vegetarian propaganda, it's not just false, it's an inversion of truth. As the proverb says, "When you point your finger, your other three fingers point back at you." Let's take a short trip through the digestive system to see why!
A Trip Through The Human Digestive System (abridged)
Briefly, the function of…
I have read and heard this many times, usually delivered in a slightly superior-sounding tone of voice: "Do you actually know how long meat stays in your colon?"
So now I do, thank you very much:)
Now, just to round out my understanding: does any part of meat actually get to the colon? Is it completely digestible? Is fat completely digestible? Do they reach the colon as some sort of primordial stew?
I enjoy the posts; keep it up! Do you want suggestions for topics?
I have been eating vegan for three years now and have never felt better. Really. Instead of having diarreah several times a year I've had it twice. Both times after eating in a restaurant where cross-contamination was most likely the culprit. I don't get heartburn anymore. And I have been constipated only one time. I have no general issue with your article on the grounds of digestion. It seems well thought out and well written. I enjoyed reading it.
"This fact alone proves that humans, while omnivores, are primarily carnivorous: we have a limited ability to digest some plant matter (starches and disaccharides) in order to get through bad times, but we cannot extract meaningful amounts of energy from the cellulose that forms the majority of edible plant matter, as true herbivores can. We can only eat fruits, nuts, tubers, and seeds (which we call ‘grains’ and ‘beans’)—and seeds are only edible to us after laborious grinding, soaking, and cooking, because unlike the birds and rodents adapted to eat them, they’re poisonous to humans in their natural state."
I don't agree with this. Sure beans and greens require some preparation. I'm pretty sure the last time I ate meat it was not in it's natural state either.
February 22, 2010
Of course there are benefits from many of the things on the fart list: vegetables provide color and flavor to meat and eggs, and I eat them daily. (In fact, I eat far more vegetables now than I did previous to "going paleo".) I'm just enjoying tweaking a few noses.
Much appreciated! I think there is demand out there for articles that are understandable outside the immediate paleo community, and that we can use to educate people who aren't already 'paleo'. Please feel free to forward them around, as that's why I write them!
Thank you! Often the best way to debunk myths isn't head-on: it's by explaining how things really work. Then the myths just seem silly. Too much dietary advice is 'rules of thumb' that don't lead to any understanding.
Meat and fat are completely digestible in the small intestine under normal circumstances AFAIK: pure carnivores have a very simple, short colon with relatively few bacteria, and its main function is to squeeze the water out of the feces.
If fat weren't digested, you'd see it floating in the toilet after you shat. This only happens if you take alli (which decreases intestinal fat absorption) or eat Olestra (which is not digestible). And collagen is well-digested: gelatin is just hydrolyzed collagen.
My understanding is that some connective tissues may be incompletely digested, but I'd have to talk to a specialist to find out exactly which. Animal protein doesn't tend to survive the pepsin/acid bath of the stomach: it's the prolamins in grains like wheat and corn that are difficult for our proteolytic enzymes to break down.
Unlike many in the 'paleo community' (whatever that is), I don't bear a grudge against vegans. I appreciate that a carefully constructed vegan diet is superior to the usual American diet of processed crap, and don't doubt that you feel better on it.
In the long term, though, I don't believe that a diet which absolutely requires supplementation with B12 and long-chain n-3 fats (both present in animal flesh) to avoid pernicious anemia and depression is either natural or advisable. And the fact remains that eating six or seven raw red beans will most likely put you in the hospital, whereas raw meat from all animals is absolutely edible in any quantity.
Raw grains and raw beans are at best non-nutritious, and at worst poisonous. There's a reason raw vegans don't eat them. (Look up lectins, trypsin inhibitors, and wheat germ agglutinin, for starters.) In contrast, meat is cooked because we're worried about contamination and it makes it easier to chew — not because it's necessary to remove poisons or for digestion.
Once again, I don't begrudge you your choice, and I'm sure it's an improvement over the SAD (Standard American Diet). But I suspect you might find a grain and bean-free, high-animal-fat diet to be even better. I know I certainly do: once I finally embraced saturated fat without reservation, my mood, energy level, and body composition improved dramatically. Besides, it's delicious!
Thanks to all of you for contributing!
One of the greatest articles in the paleo genre, congrats. A truly exhilarating read.
Found this post via Free The Animal; great stuff! Thanks for breaking it down.
An interesting note about all that "bacteria poop" that we absorb a bit of in our colons and which ruminants like cows derive most of their nutrition from: a lot of it is lipids and amino acids. That's one thing a lot of people miss, often in arguments like "cows don't need to eat protein to get big and strong;" cows ARE eating protein to get big and strong. They eat grass to feed to the bacteria that produce the proteins (and lipids) that the cows require.
That said, while bacteria poop is theoretically great and all, I'd rather get my fat and protein from some nice tender fatty meat.
BRAVO! Wonderfully done! Now, if I can just get my oh-so-committed (and oh-so-ill!) vegetarian foster daughter to actually READ it!
Great read. JS, you really have a way with simplifying it right down to understandable pieces. Thanks a lot for this article.
He blinded me, with science!
You forgot to mention an important fact that will make the cw crowd even more go ballistic. The colon bacteria produce from the rotting plant matter "arterycloggingsaturatedfat"! Butyric acid is a short chain saturated fat (which of course is not artery clogging, that was a joke) and while our gut does not produce a lot of it, it can nonetheless reach several hundreds kcal per day (showing once more that calorie counting is bullshit as the calories provided by fiber is never accounted for). Herbivorous animals derive 70% to 80% per cent of their calories from these short chain fatty acids. ONe can thus say that even cows, horses and gorillas are low-carbers.
February 22, 2010
I'm sorry to hear that. I'm convinced that vegetarianism, and especially veganism, are usually products of low self-esteem -- which is why teenage girls and young women are so vulnerable to the propaganda. Basically being vegetarian or vegan says "My life is less important than a cow's or chicken's." They're religions, not logical choices.
The irony, of course, is that agriculture kills far more animals than pastoralism: what do they think happens to the wild animals when a forest is cut down and a field plowed in its place? The animals all die, because what was feeding them is now feeding us. ("The Vegetarian Myth" covers this in detail.) Vegetarianism doesn't save the animals: it simply moves their deaths to where we don't see them. Endangered species aren't passively "in decline"...they're killed by us when we take their land and plant crops on it.
And at the end of the day, the problem isn't that I eat meat: the problem is that the average Ethiopian woman has nine children. Trying to eat less meat is a useless rear-guard action in the face of third-world population growth.
Anyway: I recommend making sure she takes EPA/DHA supplements (algae sourced, of course: sigh), B12 supplements if she isn't already...and, of course, feeding her plenty of butter, eggs, and full-fat dairy (you said she was vegetarian, not vegan). Once you address the fundamental biochemical issues underlying depression and low self-esteem, you can start working on the other stuff.
February 22, 2010
Martin, Jules, MPL, David:
Thank you! My aim here at gnolls.org is to educate people who aren't already paleo, as well as to entertain those of us who already are. I love Free The Animal, but what with all the cussing, it's not something you can generally forward around to your relatives when you're trying to explain why you won't eat their delicious home-baked muffins.
You're both absolutely correct: SCFAs (including butyrate -- found in, unsurprisingly, butter) are much of the 'bacteria poop' we're really eating. It's instructive that once you understand how digestion actually works, you end up at something relatively 'paleo' by default.
I would have loved to include that subject, but I'm worried that the article is too long already and it would have been a distraction. Perhaps I'll talk about it in another article.
Thanks, everyone, for the perceptive comments! I'm encouraged by the high level of dialogue here, and hope you'll continue to contribute.
JS, great post. Just found you via a tweet by David.
BTW, I had my gall bladder removed many years ago and have always thought the common bile duct dumped the bile into the stomach rather than the small intestine. I know when I used to have an "attack" after a high fat meal, bile is what was vomited from my stomach, after hours of excruciating pain of course. If I hadn't believed the "dietary fat will kill you" lie, my bile would not have stagnated from liquid to sludge to stones.
Heh. The reason I didn't find you from Richard's blog is because I got fed up with the in-your-face cussing and don't read him anymore.
February 22, 2010
The bile duct empties into the duodenum -- the top of the small intestine). One of bile's functions is to partially neutralize the acids of the stomach so that digestion can continue in the ileum. (Bile is rich in bicarbonates, which are alkaline.) When we vomit, the pyloric sphincter relaxes, and the top of the small intestine squeezes its contents back into the stomach...including bile.
Thanks for contributing!
Your website is pretty great, it gives a lot of sound advice, but I do worry that people may get the wrong idea and forgo eating as many vegetables as they should. It's important to note that humans are omnivores (and I would argue against the qualifier that we are primarily carnivores) as evidenced by two facts: we have evolved the molars required to process vegetable matter mechanically, and have also evolved a longer digestive tract than most carnivores precisely to give bacteria time to do their job and make vegetable components more digestible for us. True carnivores can either obtain all of their required nutrients from meat, or may consume the gut contents of their prey. We can't/don't do either of these things.
February 22, 2010
I appreciate your concern -- but I've found through experience that I eat far more vegetables on a meat-heavy diet than I did when I ate lots of grains.
An all-meat and egg diet is monotonous to me without some accompaniments. When I was eating grains, I was perfectly happy to eat a steak and a bunch of pasta dressed in olive oil or alfredo sauce, with no veggies on the plate. But if I've only got the steak to work with, I find I frequently want some veggies to add flavor and texture, or a salad to break things up.
I agree that humans are obviously not obligate carnivores. However, the fact remains that vegetables (with the exception of root starches) provide little caloric value to us: there are perhaps 70 available calories in an entire pound of mixed greens. Our colon (the only part of the digestive tract in which bacterial fermentation, and therefore the digestion of cellulose, occurs) is 17-23% of total human gut volume, whereas it's over 50% for chimpanzees (who are primarily frugivores, not folivores, and who still hunt and eat some quantity of meat).
And, contrary to your final assertion, humans can absolutely obtain all their required nutrients from meat. Here's a reprint of Vilhjalmur Stefansson's long article from Harper's Magazine in 1935, in which he and a colleague ate an all-meat diet under strict medical supervision for one entire year. (Having previously lived on an all-meat diet for years at a time during his explorations with the Inuit, who lived on such a diet for their entire lives.)
I don't wish to open the debate as to whether it's optimal for health -- but Stefansson lived to age 83 in an age without antibiotics, so it can't have completely destroyed him.
@JS - Thanks for the information. It is a great, clear presentation of the science. I've been a vegan for almost 7 years, but I constantly tell people not to be vegan for health reasons, as that is ridiculous. I have heard the meat rotting story, and even repeated that I had heard it, although I believe I have always disclaimed that I had not looked it up. I will follow up on your references and make sure not to propagate the fallacy... I realize that saying something and saying I have not looked it up does not keep it from spreading ;)
I do think your 'low self esteem' comment is off base and disappointing. I have very high self esteem, as do most of the vegans I know. I don't consider myself worth less than a cow, but I do consider a cow worth more than a convenient diet for myself. There are ways to live a long and fully healthy life as a vegan, although I do believe there is an off chance it will shorten my life simply due to lack of clear evidence/knowledge on the subject... particularly if I am not careful with my diet. That is a sacrifice I am willing to make for the countless animals that will not suffer and die for my direct consumption though. Supplements are no different than other dietary elements... you just have to be conscious of what you are eating.
The comments about farming displacing animals are misleading too, although I will read the source material you mentioned. It is true that farming does that, but humans create WAY more farmland to grow feed for the animals we breed and consume for pleasure than we would need if we ate a reasonable amount of meat. In addition, we could raise animals in MUCH better conditions if we didn't over-consume meat. Not to mention the additional waste created by the feed animals, water consumed and energy used. I can theoretically imagine there is an argument for the possibility that ruminants more efficiently convert plant nutrition and then humans can more efficiently convert their meat, ultimately leading to a more efficient chain of nutrient consumption. HOWEVER, if that is the case, people should be able to eat a relatively minimal amount of meat and very minimal plant matter in order to optimize that chain. I'm guessing people aren't going to do that, and I'm guessing people would end up over-eating meat even more if they tried, which would result in a return to bad resource usage.
To the point that humans are primarily carnivores, I believe there are a number of critical dietary components, notably vitamin C, that we only get from plant sources. I'm going to go look that up though. I am guessing you are using the term 'primarily' to mean we digest meat better and therefore should focus on it, but if there are distinct dietary needs that dictate we must eat plants, we are by definition omnivores. Perhaps there are no pure carnivores though... that's what I'm going to look up. If that is the case, then I can see using 'primarily carnivore' to describe the degree of meat consumption... otherwise it seems to me that we are either carnivores OR omnivores, and not degrees of one or the other.
Overall I have no issue with people eating meat or raising animals as food. I have a major issue with the meat industry as it exists and the mass consumption of meat that drives it. That being said, I have made my choice because I think it betters the world in many ways (although I acknowledge it is the tiniest of contributions) and in turn betters me. I am always happy to share my thoughts with others, but I realize that the 'psychology' of animals and the ethics involved is probably unknowable and certainly open to subjectivity... meaning I don't take on the subject in a militant way. I do suspect that most people, confronted with the animals they eat more directly, would KNOW the animals were suffering (mass farms) and would feel horrible for what they are directly funding. I think it is an out-of-sight-out-of-mind problem. I just don't need to see them to feel that way... over-abundance of empathy I guess.
Anyway - I have several posts on my blog/website about my vegan views if you are interested. I find that there is a lot of pretension on both sides of the debates. I do not consider myself 'better' than anyone though. I simply made changes in my personal life in concordance with how I felt about the world so that I am more at peace with the results of my actions. If people don't share the underlying views/concerns, they should certainly not be vegan, because it's a pain in the ass and unhealthy.
February 22, 2010
To skip to your last point: I absolutely agree that factory farming is an execrable practice. All of the 'paleo' sources I know of stress the importance of grass-fed beef -- and though many of them do so for purely health reasons and I can't speak for everyone, I am certainly conscious of the environmental damage caused by CAFOs. Frankly, they're an artifact of grain subsidies: if we weren't heavily subsidizing agribusiness to overproduce soy and grains, they wouldn't be cheap enough to ship from Iowa to feed cattle in California which are slaughtered and the meat shipped back to Iowa.
And if we weren't heavily subsidizing corn, soy, and wheat production with no regard to quality or nutrition (subsidies simply guarantee a price per bushel...therefore quantity is the only concern), there would be more diverse, healthy, sustainably raised food crops available for everyone. Intensive monocropping is an environmental disaster whether the corn gets fed to cattle or to people. (Or to cars.) I think both the vegetarian/vegan and the paleo community can agree on that, and I think it's a shame to spend so much energy arguing when agribusiness subsidies are at the root of both our issues.
As far as agricultural efficiency: only 18% of the USA is arable, most of it on the Great Plains, and much of it only because of water provided at great expense by environmentally destructive, government-built dams. Animals can graze just about anywhere that isn't forest. So eating meat isn't necessarily displacing row crops. I don't want to turn this into a long debate because I doubt either of us will change the other's mind, but "Meat: A Benign Extravagance" (the book that converted George Monbiot from a vegan back to an omnivore) busts several of the myths around resource consumption.
At the end of each day, some part of the planet dies so that each of us may live -- whether that's a cow being slaughtered for its meat and hide, or whether it's deer, cougars, wolves, foxes, porcupines, badgers, prairie dogs, coyotes, and hundreds of other animals starving to death because their home has been plowed under for row crops. I confront this, I understand it, and I accept it. (And it implies many things about our numbers and our future as a species.)
In closing, I admire your honesty and forthrightness. Though I disagree with your conclusion, I won't mock it, because it is far more important that we both oppose the subsidization of environmental destruction by industrial agriculture.
And if you do decide one day to jump the fence, we'll be here to welcome you home.
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