In that Vitamin B-12 is essential for the recycling of certain enzymes that maintain the health of nerve cells and counteracts homocysteine --  a compound that is associated with increased risk of stroke and atherosclerotic diseases, Anna Vogiatzoglou, from the Oxford Project to Investigate Memory and Ageing (OPTIMA) at University of Oxford (United Kingdom), and colleagues investigated the role of Vitamin B-12 status and annual brain volume loss.  For a five-year period, the researchers studied 107 community-dwelling men and women, ages 61 to 87 years, without cognitive impairment at enrollment, assessing each yearly by clinical examination, MRI scans, cognitive tests, and blood tests to assess levels of B-12, homocysteine, and other related blood markers.  The team found that people with higher Vitamin B-12 levels were six-times less likely to experience brain shrinkage (as compared to those with lower levels of the vitamin in the blood).  Writing that: "Low vitamin B12 status should be further investigated as a modifiable cause of brain atrophy and of likely subsequent cognitive impairment in the elderly,” the researchers urge for further research to ascertain whether preventing brain shrinkage may save memory function.