A new study documents that poor vitamin B12 status is a risk factor for brain atrophy and cognitive impairment and highlights the importance of its metabolites that are not routinely assessed. Higher levels of several markers of vitamin B12 deficiency, especially methlmalonic acid (MMA), homocysteine, 2-methycitrate, and cystathionine, are associated with low B12 activity. Vitamin B12 is intimately related to energy production, red cell metabolism, protection against cancer and in immune function. Elevated levels of these metabolites was associated with decreased brain volume at 5 years.