Low intakes of certain B vitamins may expose older people to a greater risk of depression. Investigators in Chicago recruited 3,500 people over 65 years old and asked detailed questions about their dietary habits. They filled out other questionnaires every few years so that the researchers could assess their level of depression. During 12 years of follow-up, about 14 percent of the participants reported symptoms of depression.
Those who had diets supplying the most vitamin B12 and B6 were least likely to develop depression. It is not clear that taking vitamins will ward off depression. In fact, taking high doses of vitamin B6 can damage the nervous system. But many medications such as Prilosec or Nexium can interfere with vitamin B12 absorption. People who must take such medications may need a supplement.
[American Journal of Clinical Nutrition, Online June 2, 2010]