"A University College London study warned that a lack of nutrients in a vegan diet, such as calcium, zinc and high-quality protein, could leave children malnourished and with 'irreversible' nerve damage. Pictured: Freshly cut celery
Dairy milk is an important source of iron, needed to make red blood cells which carry oxygen around the body. Countries such as Spain and Germany already actively warn parents against putting their children on a vegan diet.
In a paper published last month in the European Journal of Nutrition, Dr Owen and his colleagues also warned that vegan diets are particularly dangerous for pregnant women, who are more likely to have low B12 levels in the first place. Studies show that Vitamin B12 deficiency is associated with pregnancy complications, low birth weight, pre-eclampsia and miscarriages.
The paper suggests that vegans undergo regular blood tests to monitor B12 levels, alongside taking supplements. It also advises anyone who is planning on becoming pregnant or is older than 60 to consult a doctor before going vegan.
However, experts point out that a vegan diet, when combined with supplements, has a number of health benefits. Studies show that vegans are less likely to suffer from heart disease, diabetes and cancer than meat eaters.
'A responsible vegan diet can be healthy,' says Dr Owen. 'But right now, charities promoting the trend are not informing people about the essential need for B12. That needs to change.' "
