For every 10 milligram increase in the intake of vitamin B6 and for every 10 microgram increase in vitamin B12 the risk of developing symptoms of depression were decreased by 2 per cent per year, according to findings published in the American Journal of Clinical Nutrition.
The study adds to previous reports linking B vitamin intakes and a lower risk of depression. The World Health Organization (WHO) forecasts that within 20 years more people will be affected by depression than any other health problem; it ranks depression as the leading cause of disability worldwide, with around 120 million people affected.
Despite earlier reports on the potential anti-depressive benefits of the B vitamins, researchers from Rush University Medical Center in Illinois report that “very little prospective evidence from population-based studies of older adults”.
Led by Kimberly Skarupski, the researchers obtained data from 3,500 over 65 year-olds in Chicago. The volunteers were living in a normal community and were bi-racial with 59 per cent being African American. Dietary intakes were quantified using food frequency questionnaires and depressive symptoms were assessed using the 10-item version of the Center for Epidemiologic Studies Depression scale.
Over an average of 7.2 years of follow-up, the researchers noted that increased intakes of vitamins B6 and B12 were associated with a “decreased likelihood of incident depression”. The intakes of the vitamins came from both food and supplements, said the researchers.
The benefits did appear to be limited to supplement intakes, said the researchers, since no link between depressive symptoms and food intakes of B6 or B12 were observed. They also noted that folate intakes .
“Our results support the hypotheses that high total intakes of vitamins B6 and B12 are protective of depressive symptoms over time in community-residing older adults,” concluded the researchers.
While the data does indicate correlation, it does not represent causation. There is a biologically plausible link between B vitamin intake and depressive symptoms, according to a 2003 study by scientists from the University of Kuopio in Finland. Writing in BMC Psychiatry (3:17), they noted that vitamin B12 is involved in the synthesis of monoamines, some of which act as neurotransmitters.
B12 may also inhibit the accumulation of the amino acid homocysteine, wrote the Kuopio scientists, which may lead to toxic reactions that enhance depression. Indeed, data from other studies indicated that 52 per cent of depressed patients have raised levels of homocysteine.
While the biological plausibility may be there, more research is required to explore the potential link between B vitamins and depressive symptoms.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.2010.29413
“Longitudinal association of vitamin B-6, folate, and vitamin B-12 with depressive symptoms among older adults over time”
Authors: K.A. Skarupski, C. Tangney, H. Li, B. Ouyang, D.A. Evans, M.C. Morris