Helen Bond, a registered dietitian, says the large-scale Oxford study should be taken seriously, although she notes that the increased risk of 20 per cent is actually "quite small" once the sample size is taken into account (it equates to three more cases of stroke per 1000 people over 10 years).

She says that those who cut out meat entirely don't always understand the full health implications of their lifestyle choice: "I think people shouldn't just embark on a vegan diet because it's on trend, and they're following some Instagram guru. They should delve deeper and understand that there are nutrient shortfalls."

Last week, nutritionist Emma Derbyshire told the BMJ that vegans may find themselves deficient in choline, a crucial nutrient for brain health commonly found in eggs, milk and beef that influences memory, mood and muscle control. With planning, the British Dietetic Association said, it was possible for vegans to reach requisite levels, but not everyone who avoids meat plans carefully enough.

Such diets, Bond adds, are usually devoid of vitamin B12, which is found only in animal products. Without it, you run a greater risk of becoming fatigued and your immune system can be weakened, although she says "full-blown B12 deficiency is not very common in today's society". More concerning is getting enough vitamin D, the so-called "sunshine vitamin", which is important for our bones, teeth and immune system, and can be difficult to include in your diet if you are vegetarian, and very difficult if you are vegan. "Vitamin D-rich foods are mainly oily fish, eggs and things like that," Bond says. "There is some in mushrooms, but sadly [it is in] very few foods."

Bond thinks Britain is gradually moving towards a vegetarian way of life, pointing to Public Health England's latest Eatwell Guide, which stressed the health benefits of plant-based foods; according to research published at the end of last year, one in eight Britons is now vegan or vegetarian, while a fifth of the population describes themselves as "flexitarian".