The benefits were not extended to women, reports the study in the journal Nutrition, and no benefits from an increased intake of omega-3 fatty acids was observed for either gender. "To our knowledge this is the first study of these associations conducted in a non-Western population and used validated methodologies for the assessment of depressive symptoms and nutrient intake," wrote the researchers, led by Kentaro Murakami from the International Medical Center of Japan, and the National Institute of Health and Nutrition. "Although more research is needed to confirm the causality of the association, dietary modification to increase intake of folate may be an important strategy for the prevention of depression." The research adds to a growing body of research linking folate and folic acid intake to improved mood, and follows a review by scientists at the University of York and Hull York Medical School of 11 studies and involving 15,315 participants that reported low folate levels were linked to increased depression (Journal of Epidemology and Community Health, Vol. 61, No. 7). The researchers assessed dietary intakes of omega-3 fatty acids, folate, and other B vitamins among 517 Japanese subjects (average age 42.7, 208 women) using a brief self-administered diet history questionnaire (BDHQ). Symptoms of depression were evaluated using the Center for Epidemiologic Studies Depression (CES-D) scale. Thirty-six per cent of man and 37 per cent of women were found to have depressive symptoms. Murakami and co-workers calculated that increased folate levels were associated with less depressive symptoms in men, but not women. Indeed, male subjects with the highest average intake (235 micrograms per 100 kcal) were 50 per cent less likely to have depressive symptoms than men with the lowest average intake (119 micrograms per 100 kcal). No statistically significant links were reported between depressive symptoms and intakes of riboflavin, pyridoxine, cobalamin, and all or individual omega-3 fatty acids, for either sex. "We cannot rule out the possibility that the relation between folate intake and depressive symptoms may be explained by other beneficial components of a folate-rich diet, because such a diet also is usually rich in certain B vitamins such as riboflavin and pyridoxine, and the prevalence of depressive symptoms tended to decrease as intake of such B vitamins increased, albeit without statistical significance," wrote the researchers. "Because our sample was relatively small, statistical power may have been insufficient to allow the detection of associations between several dietary factors (e.g., riboflavin and pyridoxine) and depressive symptoms." The study is at odds with studies performed in Western populations that reported increased omega-3 fatty acid intake and reduced incidence of depression. Indeed, the researchers quote studies from Finland, the UK, and Australia that reported inverse associations between omega-3 intake and depression. "However, given hypotheses that opmega-3 PUFA may have an important role in neurotransmitter synthesis, degradation, release, reuptake, and binding, resulting in a pattern of neurotransmitter activity that has been associated with depression, further research in this topic is warranted," they wrote. Source: Nutrition (Elsevier) Published on-line ahead of print 3 December 2007, doi: 10.1016/j.nut.2007.10.013 "Dietary intake of folate, other B vitamins, and omega-3 polyunsaturated fatty acids in relation to depressive symptoms in Japanese adults" Authors: K. Murakami, T. Mizoue, S. Sasaki, M. Ohta, M. Sato, Y. Matsushita, N. Mishima
Increased intake of folate may reduce the incidence of depression amongst by 50 per cent, suggests a new study of over 500 Japanese subjects.