http://www.second-opinions.co.uk/vegeta ... uyGTdAe43d
Brain shrinkage among vegetarians
But, getting back to brain size, the decline which started with the advent of agriculture and our greater reliance on foods of plant origin has now seen a dramatically greater decline in those who have adopted a 'healthy', vegetarian diet.
Scientists at the Department of Physiology, Anatomy and Genetics, University of Oxford, recently discovered that changing to a vegetarian diet could be bad for our brains — with those on a meat-free diet six times more likely to suffer brain shrinkage.
Using tests and brain scans on community-dwelling volunteers aged 61 to 87 years without cognitive impairment at enrolment, they measured the size of the participants' brains. When the volunteers were retested five years later the scientists found those with the lowest levels of vitamin B12 intake were the most likely to have brain shrinkage. Not surprisingly, vegans who eschew all foods of animal origin, suffered the most brain shrinkage. This confirms earlier research showing a link between brain atrophy and low levels of B12.
Vegans are the most likely to be deficient because the best sources of the vitamin are meat, particularly liver, milk and fish.
There were two other worrying aspects to this trial. The first was at the start of the trial, the biggest brain in a vegan, at 1455 ml, was already smaller than smallest brain of someone on a ‘normal diet’, at 1456 ml.
The other aspect was even more worrying. It was that all participants had Vit B-12 which was within the 'normal' range. This suggests that the normal range is too low - and by quite large margin. I understand that, based on this study, the Japanese have raised their normal level.
Confirmation of the above study was provided the following year by another study by the Oxford Project to Investigate Memory and Ageing, the Department of Physiology, Anatomy and Genetics, University of Oxford, UK. Noting that vitamin B-12 deficiency is often associated with cognitive deficits, they reviewed evidence that cognition in the elderly may also be adversely affected at concentrations of vitamin B-12 above the traditional cutoffs for deficiency. Their suggestion is that the elderly in particular should be encouraged to maintain a good, rather than just an adequate, vitamin B-12 status by dietary means.