Low dietary intake of folate may be a risk factor for severe depression

Two studies published in the 2004 November- December issue of Psychotherapy and Psychosomatics suggest that dietary B vitamin complex has an important role as to the vulnerability to depression. In the first study, a group of Finnish investigators of the University of Kuopio found that a low dietary intake of folate may be a risk factor for severe depression.

Several cross-sectional studies have focused on the low blood folate levels of depressive patients. Nevertheless, no prospective studies have been published on the association between dietary folate and depression. We studied the association between dietary folate and cobalamin and receiving a discharge diagnosis of depression in a prospective follow-up setting. Our cohort was recruited between 1984 and 1989 and followed until the end of 2000, and it consisted of 2,313 men aged between 42and 60 years from eastern Finland. The mean intake of folate in the whole cohort was 256 µg/day (SD = 76). Those below the median of energy-adjusted folate intake had higher risk of getting discharge diagnosis of depression (RR 3.04, 95% CI: 1.58, 5.86) during the follow-up period than those who had a folate intake above the median. This excess risk remained significant after adjustment for current socioeconomic status, the baseline HPL depression score, the energy-adjusted daily intake of fibre and vitamin C, and the total fat intake. A low dietary intake of folate may be a risk factor for severe depression. This also indicates that nutrition may have a role in the prevention of depression.

In the second study, a group of Danish investigators of Aarhus University have suggested that a low level of vitamin B6 is associated with symptoms of depression. A low level of vitamin B6 might theoretically cause depression as vitamin B6 is a cofactor in the tryptophan-serotonin pathway. In the present study, we examined the association between depression and the phosphate derivative of vitamin B6 in plasma, pyridoxal phosphate (PLP). In 140 individuals, symptoms of depression were evaluated by the Major Depression Inventory, and biochemical markers of vitamin B deficiency were measured. We found that 18 (13%) individuals were depressed. A low plasma level of PLP was significantly associated with the depression score (p = 0.002). No significant association was found between depression and plasma vitamin B12 (p = 0.13), plasma methylmalonic acid (p = 0.67), erythrocyte folate (p = 0.77), and plasma total homocysteine (p = 0.16). Our study suggests that a low level of plasma PLP is associated with symptoms of depression. Randomized trials are now justified and needed in order to examine whether treatment with vitamin B6 may improve symptoms of depression.