Public health pitfalls in a vegan future?

As both a psychologist and nutritionist, I read the cover-story articles on 'A vegan future?' (January issue) with interest. They provided useful perspectives on barriers and opportunities for both vegans and non-vegans to adopt a vegan diet, seemingly to achieve full planet-saving self-actualisation, for example by overcoming the apparently misguided beliefs that eating meat is 'Nice, Normal, Necessary and Natural' - surely as powerful a quartet of cognitive horsemen to sustain habitual behaviour, like sex for example, as ever there was. I agree our increasing separation from agricultural use of animals is concerning, as was brought home to me vividly on overhearing a trainee teacher exclaim, 'Are you telling me that pork comes from pigs?!' Yet, I believe that a lack of connection to livestock farming is as likely to be permissive of veganism as it is to meat eating (vegan farmers?). However, rather than debate the merits of veganism for animal and human welfare, biodiversity or environmental sustainability, I would like to consider nutritional and public health behavioural implications.