Some people who stop eating meat have reported unpleasant effects when they return to it. Can your body forget how to digest flesh?

Eating less meat is one of the simplest ways to reduce your carbon footprint.

If everyone in the UK moved to a low-meat diet, eating less than 50g, or one Cumberland sausage’s worth of meat a day, it would save as much carbon as if eight million cars were parked for good, researchers have calculated. Data from the UK government shows that meat consumption is dropping – between 1980 and 2022, consumption of beef, pork, and lamb fell by 62% – and though the reasons cited vary, and may have more to do with rising costs than an environmental conscientiousness, more and more people are clearly experimenting with saying no to meat.

But if you go a long time without eating it, does that change your body's ability to digest it? Vegetarians and vegans sometimes post on social media, asking whether going back to meat could cause stomach pain, bloating, and other symptoms. Others weigh in with their own experiences, and a great, late-night whirlwind of curiosity and cramps is born.

However, there isn’t much research on whether consuming meat after a long break can trigger an upset stomach, says Sander Kersten, a professor of nutrition at Cornell University in the US. "A lack of evidence doesn't mean it doesn't exist, it's just that people haven't studied it," he reflects. "That's not always a satisfying situation or answer, but it's just what you have to deal with sometimes."

It is possible – though it is very rare – to be allergic to meat. Alpha-gal syndrome, in which the immune system recognises animal proteins as invaders, can lead to anaphylaxis and death. But this allergy, which can crop up after a lifetime of cheerful meat eating, is not related to switching to a low-meat diet. You can, for example, develop the condition after a tick bite.

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