I've been a veggie for years, but recently I've been told that if I ever accidentally or intentionally eat meat again I may become violently ill, because my body isn't used to it. I've eaten small mouthfuls of meat a few times when there have been order mix-ups and I've never experienced this, but maybe it requires larger quantities.

Does this statement have any basis in fact?

  • it's probably psychological, but from experience: i was about a month and 1/2 vegetarian, had an arby's burger, and felt sick the rest of the day. i had a lobster a couple weeks after that and felt a bit weird Commented Oct 27, 2018 at 0:46

4 Answers 4


Short answer:

Most likely not.

Long answer:

A sudden transition from a vegetarian diet to an omnivorous one will clearly have some effects, as any sudden change in diet will have. According to this article, these problems may appear:

A person might have a little problem if he or she started right out on a huge steak. Their body might not have sufficient levels of the right enzymes. Along the same lines, it can be hard to digest any large meal after a long fast or period of starvation.

However, there is a little (< 1%) chance of having meat allergy (independent of the fact one is vegetarian or not):

A very few – less than one percent of the population – are allergic to meats from common livestock, such as pork and beef. If a vegetarian has this kind of allergy, she could have a reaction from just a speck of these meats.

  • Is it true that they'd most likely know they had the allergy though? It's unlikely they had never had any meat in their life, unless they were raised vegan.
    – Riker
    Commented Jan 31, 2017 at 21:12
  • @EasterlyIrk Some allergies might only show up in adult age. The opposite is also true: they might disappear with time.
    – Ramon Melo
    Commented Feb 3, 2017 at 18:31
  • There are foods that your body takes years to really get used to... why would that process not reverse if it is not or hardly eaten for a long time? Commented Mar 24, 2017 at 13:49

Yes, it's possible. I wouldn't say it's a guarantee though.

I was raised vegetarian and haven't had more than two or three meals with meat in my life (tried it, didn't like it).

I can always tell when I've accidentally consumed meat. The last time was a potato dish that had bacon in it (why??). It makes me sick, but not usually for more than the rest of the day, and I've never vomited.

The specific type of sickness is quite recognizable. Some of my shorter-term vegetarian friends report similar symptoms, but not all.

I assume I'm one of the least meat-adapted people around, so yes, consuming meat can make vegetarians ill but not likely violently.

  • You might have meat intolerance.
    – Ramon Melo
    Commented Feb 4, 2017 at 0:24
  • @ramon I don't have the majority of those symptoms just recognizable bloating and GI distress. It's possible though. Commented Feb 4, 2017 at 0:25
  • It could be mild intolerance, and most people don't have all those symptoms. It caught my attention because my mother has mild lactose intolerance, and she also says she can always tell if something was prepared with milk, because of the bloating.
    – Ramon Melo
    Commented Feb 4, 2017 at 0:30
  • It's possible but I guess there's no way of knowing whether it's because I've never really eaten meat or I just happen to have it. I suppose it's possible my mom is meat intolerant and that's a subliminal reason why she raised us that way. However I still think my experience stands as an example that, yes, vegetarians can get sick on consuming meat. Commented Feb 4, 2017 at 0:55
  • Oh, no, I've never meant to dispute the validity of your answer, I have even voted it up. I mentioned meat intolerance just as a curiosity, since anyone can develop meat intolerance, even omnivores.
    – Ramon Melo
    Commented Feb 4, 2017 at 1:03

It can happen but it depends on your medical situation. I wouldn't describe it as an allergy but some people are intolerant to meat.

I literally haven't been able to stomach meat for a very long time. Initially I thought this may be psychosomatic, having caught rotavirus while having surgery as a child (and outright refusing to eat meat for some time afterwards). If I'm not aware of a few traces of meat (e.g., fat residues) it won't set me off so I think it can still be digested but I have trouble with the texture and find it nauseating to swallow or sometimes even to smell (particularly mince and red meat). Thus I've been de facto vegetarian for a long time.

I'll admit this is very rare but I have met several other people who as vegetarian for such "medical reasons". Long-term vegetarians may indeed develop an intolerance but it may not be permanent. Some Indians raised in vegetarian families have been able to reintroduce meat into their diet. Guest from other cultures fasting from Ramadan (and abstaining from eating meat) are advised to gradually reintroduce it into their diets (fish, white meat, and then red meat). I found that I can tolerate fish products better and practice Pescetarianism (particularly with Asian cuisine where it difficult to avoid).

Thus I think it does occur but it is possible to reintroduce meat into your diet gradually, even if you do experience intolerance symptoms. Becoming vegetarian is not a permanent transition, it is reversible.


I know of no factual basis for these statements whatsoever. I have heard them perpetuated many times at many places and consider them to be some sort of urban legend.

As indicated in Alexei's answer, there are people with meat allergies, but for these people, meat would be the "illness", not the transition to it.

The only reason for feeling unwell after eating meat for someone following vegetarian diet that I can see is a psychological one. I have experienced slight nausea and stomach pains after discovering that in the foods I ate, there were parts of animals, like their fat or bones/tendons (these are used in my country to give a certain "taste" to soups). It still does not match the violently part of "violently ill" though.

EDIT: As Azor-Ahai pointed out, in his case (vegetarian since he was born), the effects of eating meat can be physical as well, due to the body not being used to break down meat at all. I suspect this would be the case with long-term (10+ years) vegans/vegetarians as well. Do not take my word on it though.

  • As I answered below, I get sick accidentally consuming meat, even when I don't know it had meat (I found out a few days later in my example below). Commented Feb 3, 2017 at 20:01
  • Very interesting, even more after considering your rather rare upbringing. It may not be all psychological then. Commented Feb 3, 2017 at 20:04
  • Yeah. I'm not a stomach scientist but I assume I produce low amounts of the proper enzyme so eating meat is uncomfortable to digest. It honestly took me like a day and a half to digest my first meat burger. It was gross. Unfortunately, it's not something you can really test in a scientific manner. Commented Feb 3, 2017 at 20:10
  • Yes, you are probably right. Although enzymes like protease are found in certain fruits, it is true that in cases like yours the body can respond with sickness-like symptoms. I will update my answer to reflect this. Thans for pointing that out. Commented Feb 3, 2017 at 20:19

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