A study by Bristol University of almost 10,000 men in the south west of England found that those who gave up meat were almost twice as likely to suffer depression as those on a conventional balanced diet.I suspect eliminating meat or all animal products from the diet is a naturopathic attempt to self-treat depression. People I've known who tried it were already neurotic and grasping at straws. As the study shows, it doesn't help much but may generate some placebo effect.
The paper, in the Journal of Affective Disorders, said a veggie diet led to lower intake of vitamin B12 and greater consumption of nuts rich in omega-6 fatty acids, which may be linked with greater risk of mental health problems.
The authors discovered just over half of vegans and 7 per cent of vegetarians were deficient in vitamin B12 – which is found in red meat and plays an important role in producing brain chemicals that influence mood.
However the authors did not rule out that the decision to adopt a vegetarian diet may be a symptom of depression.
N.B., I wasn't certain whether to title this post "Weird Dietary Science" or "Weird Mood Disorder Science;" it partakes of both disciplines.