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More and more people in the UK are now choosing a plant-based diet, with estimates there are as many as 540,000 full-time vegans joined by a further 250,000 every January doing the Veganuary challenge.

While the benefits for the planet are well documented (earlier this month the UN issued a report saying switching to a plant-based diet can help fight climate change) are there negative health implications of not eating meat?

A new study published in the British Medical Journal (BMJ) raises concerns about vegans being deficient in choline - a nutrient critical for brain health - as it is mainly found in animal foods.

The study says moving away from animal-rich diets could have “unintended consequences” for levels of choline which is critical for brain health particularly during foetal development. It also influences liver function.

The body produces some of its own choline in the liver, but it is not enough to meet human requirements and must be supplemented with diet.

Primary sources of choline include beef, eggs, dairy, fish and chicken. Much smaller amounts can be found in nuts, beans and cruciferous vegetables such as broccoli.

Choline is presently excluded from UK food composition databases, major dietary surveys, and dietary guidelines – meaning the government is not monitoring levels of the nutrient in the population.

“Given the important physiological roles of choline and authorisation of certain health claims, it is questionable why choline has been overlooked for so long in the UK..."”

Dr Emma Derbyshire, of Nutritional Insight, a consultancy specialising in nutrition and biomedical science, said the Government had failed in not monitoring this or making recommendations to those on vegan diets.

She says: “Given the important physiological roles of choline and authorisation of certain health claims, it is questionable why choline has been overlooked for so long in the UK.“

Derbyshire said more needs to be done to educate healthcare professionals and consumers about the importance of a choline-rich diet.

Supplementation strategies should be considered, particularly during pregnancy, when choline intakes are critical to infant development.

She added: “This is now more important than ever given that accelerated food trends towards plant-based diets/veganism could have further ramifications on choline intake/status.”

The UN report, written by 107 scientists, said switching to a plant-based diet could help climate change but stopped short of explicitly calling on everyone to become vegan or vegetarian (but did highlight the benefits).

UK scientists, including the government’s chief environment scientist, have also made similar calls for a reduction in meat consumption.