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Old 19 November 2008, 10:47 PM
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Default Do vegetarians get sick from eating animal products?

I've heard a lot of anecdotal evidence to the effect that long-time vegetarians or vegans can become sick after eating meat or other animal products from which they have abstained. I've also heard several half-baked theories on why this might be, but I take issue with those I've heard, and I can't seem to find anything backed by a proper study.

Here are the explanations I've heard, and why I doubt them:

1) It's psychosomatic and/or coincidence. This one seems the most credible to me; either people get sick from something else and blame the meat, or get sick at the realization that they ate meat. But I've heard so many people describe getting sick after unwittingly ingesting animal products (not finding out that there was butter or chicken stock in what they'd eaten until much later) that I suspect there may be more to it than that.

2) Vegetarians/vegans stop producing enough enzymes to digest large quantities of protein. First of all, most of these stories come from lacto/ovo vegetarians, who still consume animal products that are about as rich in protein as the meat they shun; according to this site, hard cheeses have exactly as much protein, pound for pound, as meat, chicken, and fish. In my experience, many vegetarian dishes compensate for the lack of meat by piling on dairy and eggs, so it seems unlikely to me that l/o vegetarians get significantly less protein than regular ol' omnivores. Also, even vegans can get more protein than they need, if they're fond of beans and tofu, and I never hear similar stories about veg-heads puking after gorging on Morningstar burgers. Anecdotes are not data and all, but it still makes me wonder.

There is a variant on this pertaining specifically to milk that does intrigue me. I know that the ability of many people (mostly those of European descent) to continue to digest lactose into adulthood is a quirk peculiar to humans, and likely the result of generations of domesticating goats, sheep, and cattle and drinking their milk. Lactose tolerance requires the production of a particular enzyme that isn't used for anything else (unlike the enzymes that digest meat proteins, which I believe are the same enzymes used for all proteins) and it appears to be heritable. But perhaps even a person with the genes to continue producing that enzyme could stop, if he stopped consuming lactose. I'd love to find some serious research on the subject.

3) Conventionally farmed animal products, and meat in particular, are so lousy with hormones, antibiotics, pesticides, Salmonella, Mad Cow Disease, and the fear and terror coursing through the poor creature's nervous system the instant before it was slaughtered, you monster, you, that one must build up resistance to the toxins over time. Once you have purged yourself of these impurities, your body will react to them as it should, by trying to rid itself of them by whatever means necessary. You can probably guess what I think about this one.

I asked this question on the vegetarian message board I visit whenever I need a recipe for a vegan cake, or feel like tearing out my hair and screaming "posting something 749 times does not make it true!!!" But, well, you know. I got a lot more personal anecdotes, some rehashing of the same theories I found through a cursory Google search, outlined above, and no useful pointers on where I might find some substantial research. I know there are several vegetarian Snopesters and others with backgrounds in nutrition and human biology. Can anyone help me out here?
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Old 19 November 2008, 11:03 PM
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I think #2 is closest to the mark, IMO. I've found that I get sick anytime I have a change in diet.
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Old 19 November 2008, 11:08 PM
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Don't know why (although I strongly suspect #2) but as anecdotal evidence, I was retching and throwing up a few hours after accidently getting a bite of my husband's beef burrito thinking it was my bean burrito.
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Old 19 November 2008, 11:09 PM
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Quote:
Originally Posted by Beachlife! View Post
I think #2 is closest to the mark, IMO. I've found that I get sick anytime I have a change in diet.
Maybe, but it wouldn't be so broad. Proteins are a necessary part of any human diet, and found in a lot of other foods besides meat (as Esprise Me mentioned).

I guess it could be something more specific, however. Or even more broad - not just the protein, but a change in general diet as you alluded to. Really, if I had to guess, it would be the body not being used to digesting the animal fats (since I know overly fatty foods can cause an upset stomach).

However, if there is truth to this, I would bet on psychosomatic.

Last edited by Jahungo; 19 November 2008 at 11:25 PM.
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Old 19 November 2008, 11:25 PM
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I've occasionally ingested meat by accident, and not noticed any particular ill-effects, if reverse anecdotal evidence has any value. I once ate most of a chicken patty in a restaurant thinking "This is the worst eggplant I've ever had in my life."
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Old 19 November 2008, 11:39 PM
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Quote:
Originally Posted by Chloe View Post
I've occasionally ingested meat by accident, and not noticed any particular ill-effects, if reverse anecdotal evidence has any value. I once ate most of a chicken patty in a restaurant thinking "This is the worst eggplant I've ever had in my life."
And that answers the questions "Which came first? The chicken patty or the eggplant?"
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Old 20 November 2008, 12:08 AM
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Anecdotal evidence:

I can think of at least two vegetarian acquaintances that claimed they didn't feel well when they ate meat.
Then again, I was a vegetarian for about a year. No meat and not much eggs or dairy. When I started eating meat again I didn't have any problems.

Maybe what's happening is this: If you aren't buttering or frying most of your food, a vegetarian diet (especially one without diary) is rather low fat. A lot of meat products (hamburger, bacon, sausage etc.) are fatty. Maybe it's a reaction to the sudden dose of fats?
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Old 20 November 2008, 01:19 AM
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I don't have any real evidence for this (and so possibly shouldn't be posting it here), but what I have heard is that the beneficial bacteria normally present in the digestive tract, which help in digestion, vary according to the usual diet; vegetarians don't have the right balance of bacterial species to help them digest meat, and so don't digest it well.

It's also possible that (in societies in which people choose their diets as individuals) those people who don't, for whatever reason, digest meat well are more likely to become and remain vegetarians, as these would be the people who feel healthier on a vegetarian diet than on a diet including meat. There does seem to be a good deal of individual variation on this issue.


thorny (omnivorous) locust
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Old 20 November 2008, 01:29 AM
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Another anecdote, the writer of Tomato Nation actually became vegetarian because she developed an inability to digest red meat. It's not accurate to say "Can't digest protein" as you pointed out. Lactose (as in Lactose Intolerance, the inability to digest dairy products) is a sugar. But people who are lactose intolerate are usually perfectly able to digest fructose and sucrose. Likewise, it can be possible to digest one type of protein while being unable to digest others.
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Old 20 November 2008, 04:18 AM
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I always thought it had something to do with the fat as well. The few times I've had something with meat in it that I didn't know it was really greasy. I get the same kind of stomach mess if I eat too much pizza. Outside of the occasional pizza or Chinese take out I don't eat a lot of greasy foods.
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Old 20 November 2008, 04:58 AM
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Quote:
Originally Posted by Anyte View Post
Another anecdote, the writer of Tomato Nation actually became vegetarian because she developed an inability to digest red meat. It's not accurate to say "Can't digest protein" as you pointed out. Lactose (as in Lactose Intolerance, the inability to digest dairy products) is a sugar. But people who are lactose intolerate are usually perfectly able to digest fructose and sucrose. Likewise, it can be possible to digest one type of protein while being unable to digest others.
kind of OT, but this solves the discussion I was having the other day on whether a person could be allergic (or at least, intolerant) to meats or not.
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Old 20 November 2008, 05:10 AM
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Having thought about the question in the OP a few times myself I think that it is most likely a question with more than a single answer.

I think for some people it might definitely be psychosomatic, in much the same way someone might wolf down a foreign dish and suffer no ill effects until they realise they've just eaten a large bowl of testicle and eyeball soup.

I think for others it may be an issue processing the specific proteins found in meats (which is what may have lead them to become vegetarian/vegan in the first place). For others it might be more to do with the fats as blucanary suggests.

ETA: I reread the thread and this caught my eye...
Quote:
Originally Posted by Chloe View Post
I've occasionally ingested meat by accident, and not noticed any particular ill-effects, if reverse anecdotal evidence has any value. I once ate most of a chicken patty in a restaurant thinking "This is the worst eggplant I've ever had in my life."
You're kidding, right? It appears the restaurant you ate at has an interdimensional kitchen that crosses time and space! A couple of months ago while we were dining with friends, a dish that was supposed to be chicken came out as eggplant instead!! It's like some kind of quantum entanglement!

Ok... I confess that the similarities actually aren't that thrilling. Chloe's anecdote involved a switcheroo of an eggplant patty with a chicken patty. My friend ordered a chicken-based meal and was given the entirely wrong thing rather than eggplant-for-chicken substitution of the correct dish (he ordered a chicken parmigiana and instead got a vegetarian lasagna featuring a large quantity of eggplant).

Still, as my late grandfather always said -- never let facts get in the way of a good story.

Last edited by Salamander; 20 November 2008 at 05:22 AM.
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Old 20 November 2008, 10:27 AM
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I agree with the greasiness theory, and also what you're used to eating. That accounts for most of my experience. I've been vegan or vegetarian at times, and then when I'd return to eating meat, if it was fatty, like fast food, it upset my stomach, but not if it was lean. Never had trouble with poultry, though, unless it was also fried or fatty.

However, I also had problems when I wasn't vegan when I'd eat cheap cuts of meat - not even fatty ones. Had trouble digesting cheap steaks, but not expensive ones or other, non-red meat. I think your guts get used to the things you eat, and when you change, that can give you grief. Perhaps the lack of right kinds of bacteria that have been previously mentioned.

My wife says fast food burgers make her have to go, and pretty quickly, kind of like a really lactose intolerant person and milk. The woman has an iron stomach - she eats killer chili peppers almost daily - but can't handle greasy burgers. She's okay with lean ones of any variety - beef, bison, turkey, salmon - that we cook at home, but I'm sure McDs, etc, aren't using extra lean meat.

I can eat fast food burgers, or even hot dogs - in both cases, I lean toward leaner varieties - but one thing that has always grossed me out, and seemed too greasy to eat at all is the kind of link sausages they serve at Denny's and such breakfast places. Totally fatty and disgusting to me. I can eat the bacon, though, so who knows? It could be a combo of attitude and what I'm used to. Fortunately, I seldom go out to breakfast, and I prefer Cheerios, anyway. Most places aren't even serving breakfast by the time I get up!

Regarding non-meat fats, yeh, I think some pizzas can be way too greasy. I always dab off the grease from pepperoni, but sometimes just the cheese is too much. When I make pizza or quesadillas at home I usually use reduced fat cheese. I generally don't eat the skin or batter on fried chicken, either, and in the past, I had a few bad experiences with fried foods, but I think it had to do with my Crohn's.

We can be non-red meat, non-fatty meat eaters, and still consume a lot of fats, mostly without getting disgusted or sick like some of us do with meat products. I have no trouble with ice cream, though I do have to take lactaid, and try to get the lower fat, lower sugar kind, but I'm one of those people who scrapes most of the frosting off of cake, too (unless it's chocolate)! Way too fatty - and sweet - for me. What's that stuff made of - shortening and sugar? Blech!
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Old 20 November 2008, 01:31 PM
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Quote:
Originally Posted by surfcitydogdad View Post
I always dab off the grease from pepperoni
I remember ordering a cheese & pepperoni pizza from a certain pizza store, when the pizza was delivered I opened the box to discover most of the pepperoni slices had curled up slightly so they resembled a shallow bowl. Each one curled up in such a manner was nearly filled with grease!

I used a paper towel to gather up all the grease and the thing was pretty well soaked. I did eat it but we referred to that store's cheese & pepperoni pizza as the "insta-coronary pizza" from that point forth.
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Old 20 November 2008, 01:42 PM
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Originally Posted by thorny locust View Post
It's also possible that (in societies in which people choose their diets as individuals) those people who don't, for whatever reason, digest meat well are more likely to become and remain vegetarians, as these would be the people who feel healthier on a vegetarian diet than on a diet including meat.
I never made a conscious choice to become a vegetarian; I just never liked meat even as a young child. I have always found beef and pork difficult to digest. Those meats make me gassy, constipated, and I hate the texture of them. On the other hand, I like chicken and have never had any problems digesting poultry. So my diet is predominantly vegetarian with occasional chicken and fish. I can eat small amounts of ham in a sandwich without any problems, but too much gives me gas.
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Old 20 November 2008, 03:11 PM
Nick Theodorakis Nick Theodorakis is offline
 
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Quote:
Originally Posted by Anyte View Post
Another anecdote, the writer of Tomato Nation actually became vegetarian because she developed an inability to digest red meat. It's not accurate to say "Can't digest protein" as you pointed out. Lactose (as in Lactose Intolerance, the inability to digest dairy products) is a sugar. But people who are lactose intolerate are usually perfectly able to digest fructose and sucrose. Likewise, it can be possible to digest one type of protein while being unable to digest others.
With perhaps a couple of rare exceptions (e.g., chymosin, which coagulates milk), I can't think of any digestive proteases that can distinguish between plant and animal proteins.

People who have urea cycle disorders need to severely limit or monitor their total protein intake, but it doesn't matter where their protein comes from.

Some people carry recessive genes for some of these disorders may be mostly asymptomatic, but may nevertheless feel unwell if they consume large amounts of protein.

Nick
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Old 20 November 2008, 04:57 PM
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I had a battered sausage a year or so ago; the first one I'd had in what must be at least 10 years.

I couldn't finish it, it made me feel sick.
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Old 20 November 2008, 08:07 PM
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I've always gotten sick from eating red meat, chicken and pork. My Mum is the same so we are both pescetarian (fish eating 'vegetarians'). We both also find that we feel ill when we eat a large amount of protein so for us I'd say it's protein related. If it was because of issues with fatty foods then we wouldn't be able to eat fish and chips without problems.

I've had the diagnostic tests (colonoscopy; aka the bum camera ) and the tests revealed that I don't have enough of the protein digestion enzyme and have almost none of the lactose one (explains the severe reactions to lactose). According to the gastro-enterologist (sp?) the reason that we have less trouble with plant based proteins has something to do with the smaller concentration of protein in the food ie with plant based protiens there is a bunch of other stuff accompanying it (fiber etc) meaning that the body takes more time to extract it so it is easier for us to handle. He also recommended egg whites as a primary source of protein because apparently it is the simplest and most easily digested form of protein.

He doesn't know why seafood seems to be OK for us but suggested that it is possible that other meats contain something that is toxic in some way to us or we are lacking some form of bacteria needed to break it down properly. Not all gut flora documented have known functions.

I would rule out the psychosomatic element in my case because I want to be able to eat meat. It smells good, looks good and other people seem to enjoy it so much. The smell of cooking bacon is so darn tempting but the consequences keep me from trying to eat it. There have been a few occasions when some idiot has assumed that I don't eat meat by choice and has decided to prove it's all in my head by disguising meat in food and giving it to me. Each and every time I have gotten erruptively ill and one time needed hospital treatment (an insulin dependent diabetic who can't keep anything down can sometimes get into a world of trouble).

Last edited by Jelly Bean Queen; 20 November 2008 at 08:09 PM. Reason: left out a word and because spelling will never be my secret talent.
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Old 20 November 2008, 08:33 PM
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FOAF anecdotal account:- One of my friends S was a strict lacto-vegetarian. One of his "friends" A fed him spicy mincemeat, and told him it is spicy minced cauliflower. A fessed up to S the next day, and S threw up. So, based on S's account, it is psychological.


I was vegetarian as a kid. I think I had undercooked meat once, and it was a bit slimy, so eating meat would trigger thoughts of the undercooked meat. FOr me it was purely psychological. I got over it eventually.
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Old 20 November 2008, 08:50 PM
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I'm not anything resembling a vegetarian but I have had some severe stomach problems from eating cheese in South America, even in very "clean" and "western" restaurants. Whatever the strain of bacteria used for that cheese, it doesn't agree with my gut flora. I imagine that by eating small amounts of it (rather than, say, a whole pizza) I'd get used to it - but in time, I'd probably lose this, just like many strict vegetarians could lose their ability to eat a lot of meat, without adverse effects.
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