Can Eating Meat Really Make Vegetarians Sick?

So do people who forgo meat then temporarily lose their ability to digest it, or is that just a myth?

People choose to give up meat and become vegetarians for myriad reasons. Sometimes it's to cut back on the cholesterol and saturated fat found in their favorite meat products; other times it's because they're opposed to the environmental and moral impact of the meat industry itself. Likewise, there are just as many reasons why a number of vegetarians decide to go back to an omnivorous lifestyle. As a vegetarian, I'll freely admit that there are times when few things sound more satisfying than a big ol' cheeseburger. But part of my reluctance to return to the world of meat (other than, you know, my reasons for becoming a vegetarian in the first place) stems from the potential havoc something like a cheeseburger would wreak on a digestive system that hasn't confronted red meat in many years.

The Digestive System Doesn't Like Change
Within the human gastrointestinal tract lie tons of bacteria called "gut flora" that help break down anything that's consumed. Some types of flora build up more than others, based on one's regular diet. The same is true of the enzymes that GI tract cells secrete and that also help with digestion. So if someone stops eating meat for a significant amount of time, it's possible that the amount of enzymes dedicated to animal-protein digestion might reduce a little to compensate for the increase of other food groups in the system. But that's by no means a permanent condition. "The gut senses what it needs to secrete," says Rania Batayneh, a nutritionist and wellness coach based in San Francisco. "If you haven't consumed a type of food in a long time and you eat it, it just might take a longer time to digest, especially with meat."

Toni Bloom, a registered dietician who teaches sports nutrition at San Jose State University, also believes it has more to do with the diet shift. "Anytime you put something different in there, it can upset the balance. It's not a bad thing; it's that your body has to adjust," she explains. Basically, making radical changes to one's diet is going to throw the digestive system for a loop, at least in the beginning. Take someone who subsides mostly on junk food: One day, he decides to eat more healthfully and fills up on salads, whole grains, and beans instead. Even though he's adopted a much better diet, it's likely he'll experience bloating, gas, and nausea—the same symptoms vegetarians often report after eating meat again for the first time—for the first few days. That's because his system has to work harder than usual to break down those unfamiliar, fibrous substances.

But not only is the human body resilient, it's a fast learner, to boot, and it gets used to the change in diet relatively quickly. The same holds true for former vegetarians—many of them stop experiencing symptoms not too long after they begin eating meat again.

Considering the Bigger Picture
Not all vegetarians-turned-omnivores feel sick after their first meal back, because we don't all have the same diets and therefore don't digest everything the same way and with the same results. Vegetarians who eat a balanced diet (that means not relying solely on cheese and bread) tend to consume less fat than their meat-eating friends, simply because animal proteins have high saturated fat contents compared with plant proteins, like lentils. So a vegetarian who goes from a low-fat diet to a cheeseburger might have more physical issues than one who chooses a lighter return meal. "Saturated fat can cause a lot of discomfort in digestion, because it's very heavy on the system and a lot of saturated fat comes from animal products," Batayneh shares.

Bloom notes that it's important to consider how reintroducing meat into one's diet affects the rest of his or her food choices. "If someone's making chicken a bigger part of dinner, my guess is, they're also having a smaller portion of [grains and vegetables]," she says. "It might not be the fact that they added chicken, but that they're eating less produce or grains." Just as eating a big piece of fatty meat increases one's chances of stomach upset, so does focusing too much on one food group and throwing off the gastrointestinal tract even more.

Think Skinless Chicken, not Bacon Cheeseburger
So how does a vegetarian who wants to eat meat again minimize his or her chances of digestive problems? Both Batayneh and Bloom believe that gradual changes and small portions are key. Bloom suggests starting with a few pieces of meat on a salad or making it a side dish so that the diet is changed as minimally as possible for the first few days. Batayneh tells her clients who make the switch to eat fish and lean poultry, like chicken and turkey, because those are the easiest kinds of meat to digest; opt for lean cuts of pork and beef as well. She reminds them to keep portions small and incorporate them into the vegetables and grains they already eat regularly. "Have the same things you're used to when adding something a little different, to ease the transition," she says.

For any vegetarians out there who want to take a break from vegetarianism, take comfort in knowing that digestive issues aren't set in stone and that your systems will return to stasis after a few days. On the other hand, that also means that a cheeseburger, steak, or any of those other meaty foods you've been craving probably shouldn't be your welcome-back meal if you want to avoid bloating and nausea. Instead, opt for something simple and light—your stomach will greatly appreciate it, even if your taste buds don't.

See: The Perfect Gourmet Grilled Cheese: 25 Delicious Recipes To Try

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