You know how it is - no buses in sight, then two come along at once.  It's been a bit similar for good research on diet and depression.  There have been plenty of studies on individual components of diet and mood (e.g. fish, folate, other B vitamins), but very little on the possible psychological effects of diet as a whole.  Then in October's edition of Archives of General Psychiatry, along came:

Sanchez-Villegas, A., M. Delgado-Rodriguez, et al. (2009). "Association of the Mediterranean Dietary Pattern With the Incidence of Depression: The Seguimiento Universidad de Navarra/University of Navarra Follow-up (SUN) Cohort." Arch Gen Psychiatry 66(10): 1090-1098.  [Abstract/Full Text]  
Context: Adherence to the Mediterranean dietary pattern (MDP) is thought to reduce inflammatory, vascular, and metabolic processes that may be involved in the risk of clinical depression. Objective: To assess the association between adherence to the MDP and the incidence of clinical depression. Design: Prospective study that uses a validated 136-item food frequency questionnaire to assess adherence to the MDP. The MDP score positively weighted the consumption of vegetables, fruit and nuts, cereal, legumes, and fish; the monounsaturated- to saturated-fatty-acids ratio; and moderate alcohol consumption, whereas meat or meat products and whole-fat dairy were negatively weighted. Setting: A dynamic cohort of university graduates (Seguimiento Universidad de Navarra/University of Navarra Follow-up [SUN] Project). Participants: A total of 10,094 initially healthy Spanish participants from the SUN Project participated in the study. Recruitment began on December 21, 1999, and is ongoing. Main Outcome Measure: Participants were classified as having incident depression if they were free of depression and antidepressant medication at baseline and reported a physician-made diagnosis of clinical depression and/or antidepressant medication use during follow-up. Results: After a median follow-up of 4.4 years, 480 new cases of depression were identified. The multiple adjusted hazard ratios (95% confidence intervals) of depression for the 4 upper successive categories of adherence to the MDP (taking the category of lowest adherence as reference) were 0.74 (0.57-0.98), 0.66 (0.50-0.86), 0.49 (0.36-0.67), and 0.58 (0.44-0.77) (P for trend <.001). Inverse dose-response relationships were found for fruit and nuts, the monounsaturated- to saturated-fatty-acids ratio, and legumes. Conclusions Our results suggest a potential protective role of the MDP with regard to the prevention of depressive disorders; additional longitudinal studies and trials are needed to confirm these findings.

And then, in November's British Journal of Psychiatry, we had the study by Akbaraly & colleagues who were a month late in their statement " ... to the best of our knowledge, no previous prospective study has investigated the association between dietary patterns and the occurrence of depressive symptoms."

Akbaraly, T. N., E. J. Brunner, et al. (2009). "Dietary pattern and depressive symptoms in middle age." The British Journal of Psychiatry 195(5): 408-413.  [Abstract/Full Text]
Background: Studies of diet and depression have focused primarily on individual nutrients.  Aims: To examine the association between dietary patterns and depression using an overall diet approach.  Method: Analyses were carried on data from 3486 participants (26.2% women, mean age 55.6 years) from the Whitehall II prospective cohort, in which two dietary patterns were identified: ‘whole food' (heavily loaded by vegetables, fruits and fish) and ‘processed food' (heavily loaded by sweetened desserts, fried food, processed meat, refined grains and high-fat dairy products). Self-reported depression was assessed 5 years later using the Center for Epidemiologic Studies - Depression (CES-D) scale.  Results: After adjusting for potential confounders, participants in the highest tertile of the whole food pattern had lower odds of CES-D depression (OR = 0.74, 95% CI 0.56-0.99) than those in the lowest tertile. In contrast, high consumption of processed food was associated with an increased odds of CES-D depression (OR = 1.58, 95% CI 1.11-2.23).  Conclusions: In middle-aged participants, a processed food dietary pattern is a risk factor for CES-D depression 5 years later, whereas a whole food pattern is protective.

What excellent news!  We now have pretty solid reasons to recommend healthy diet as a way of reducing our risk of developing depression (and quite probably as a way of getting better if we are depressed).  It adds a major extra component to the useful interventions we have for treating depression and - instead of potentially having unpleasant side-effects - it is an intervention that we should be encouraging everyone to make anyway because of the huge benefits provided by healthy diet for our physical health.  See for example earlier blog posts on "Does healthy lifestyle really make a difference?", "Preventing cancer through life style choices" and "Would you like to be 14 years younger - it's largely a matter of choice!".

Notice too that it isn't just the antidepressant effects of a good diet that we can recommend, we should also warn against the pro-depressant effects of a bad diet (as found by Akbaraly et al above).  This chimes with Westover & Marangell 2002 paper entitled "A cross-national relationship between sugar consumption and major depression?"  and the recent, fairly chilling paper by Moore et al  "Confectionary consumption in childhood and adult violence." 

We have an awful lot of ground to make up.  Our basic lifestyle choices tend to be horribly poor.  See the posts "Common sense isn't common"  and "Vegged out and fruitless".  Happily there is lots of good information and advice available.  See the posts and associated links "Eat 5 to 9 portions of fruit & veg daily", "How to cut down on fats" and the already mentioned "Preventing cancer through life style choices".  Trichopoulou et al's recent analysis of health benefits from different components of the Mediterranean diet particularly highlights the value of reducing consumption of meat products and increasing vegetables, fruits and nuts, olive oil, and legumes.  This kind of dietary pattern can even help to reduce global warming!  See this month's blog post "Handouts and internet resources for healthy eating" for a wealth of further relevant information.