B vitamins slow the rate of accelerated brain atrophy in elderly.

There is a stereotype that as people age their mental or cognitive status begins to decline.  The fact is that sixteen percent of those over 70 years of age have mild cognitive impairment.  One factor that seems to be associated with cognitive impairment as we age is an accelerated rate of brain atrophy.  The brain literally begins to shrink.  High blood levels of homocysteine, an amino acid often associated with an increased risk of heart disease, has also been shown to be a risk factor for brain atrophy, cognitive impairment, and dementia.
B-vitamins, specifically, B12, B6 and folic acid have the ability to recycle homocysteine and decrease blood levels of the amino acid.  Scientists at the University of Oxford have used MRI scans to show the ability of these B-vitamins to slow the rate of atrophy.  By supplementing B6, B12, and folic acid participants were able to lower blood homocysteine levels and showed a decreased rate of brain atrophy.

citation link: http://www.ncbi.nlm.nih.gov/pubmed/20838622