A study, by the University of Oxford, found 20% higher rates of stroke in vegetarians and vegans, than in meat eaters: the equivalent to three more cases of stroke per 1,000 people.
On the plus side, those following plant-based diets had 10 fewer cases of heart disease compared with their meat-eating counterparts.
Researchers believe the increased risk of stroke could be down to lower levels of vitamins among the vegetarian and vegan participants.
Study authors also suggested that low blood levels of total cholesterol among vegetarians and vegans may play a role.
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The research, published in the British Medical Journal, looked at 48,000 people over an 18-year period.
Half of the participants were meat-eaters; just over 16,000 vegetarian or vegan and 7,500 described themselves as pescatarian (fish-eaters).
They were asked about their diets, when they joined the study, and again in 2010. Medical history, smoking and physical activity were taken into account,
The results revealed that people on vegan and vegetarian diets are have a 22% lower risk of heart disease than meat eaters, while those who followed a pescatarian diet, fish but no meat, have a 13% reduced risk.
“We observed lower rates of ischaemic heart disease in fish eaters and vegetarians than in meat eaters, which appears to be at least partly due to lower body mass index and lower rates of high blood pressure, high blood cholesterol, diabetes associated with these diets,” study authors said of the research.
However, researchers were unable to prove whether the effect is down to their diet or some other aspect of their lifestyle.
Study authors said further investigation is needed before changing diet guidelines.
The NHS Eatwell Guide shows the different types of food vegetarians and vegas should try to eat in order to have a healthy, balanced diet, and in what proportions.
Recent figures have revealed that increasing numbers of adults are switching to plant-based diets, and there are now thought to be 540,000 vegans in Britain, up from 150,000 a decade ago.
The new research comes as it was revealed earlier this year that unhealthy diets are responsible for 11 million preventable deaths globally per year.
The study, published in The Lancet, revealed people were eating too much of the wrong types of food and not enough of the healthier stuff.
What’s more the research found that eating and drinking better could prevent a whopping one in five deaths around the world.
The research follows a further study released earlier this year revealing that meat consumption needs to be reduced to just 7g a day in order to save the planet and reduce premature deaths.
While research last year found eating a diet high in red meat could increase levels of trimethylamine N-oxide (TMAO), a chemical generated in the gut and linked to a higher risk of heart disease.