Brain shrinkage due to dehydration has been linked with dementia. Now there is a potential link between B-12 deficiency and brain shrinkage. Reportedly, this was first linked to brain shrinkage in a 2008 study led by Oxford University emeritus professor of pharmacology A. David Smith. Since then, multiple studies have linked brain shrinkage with dementia. A 2011 study reported in Neurology by researchers at Chicago's Rush University Medical Center found that older people with B-12 deficiency measured by blood tests not only had the smallest brains but also the lowest scores on tests measuring thinking, reasoning, and memory. More tomorrow.