Older adults who take supplements of vitamins B6 and B12 are less likely to suffer from depression. Research published in the American Journal of Clinical Nutrition does not prove that taking vitamins B6 and B12 are the sole cause of this reduced risk of suffering from depression. However it is a reminder that older adults are not exempt from watching their diets and being careful to watch their nutrition.
Supplements are not the only way to be assured of getting enough of vitamins B6 and B12. B6 is found in many foods, like bananas, beans, chicken, meat, peanut butter and fish such as salmon and tuna. B12 is found in beef, dairy products and some fish, like trout and salmon.
"Both B6 and B12 are involved in healthy nervous system function, and overt B12 deficiency causes a neurological syndrome that includes problems with thinking and memory, as well as depression symptoms."
http://www.reutershealth.com/archive/2010/06/18/eline/links/20100618elin002.html