Some research has suggested a link between nutrients like fatty acids and B vitamins and depression, but researchers from University College, London, saw there was a dearth of studies looking at overall diet and depression. Studies on the effects of the vegetable- and fish-laden Mediterranean diet have investigated links between food and Alzheimer’s and Parkinson’s diseases, but not depression.
For the new study, published in the British Journal of Psychiatry, they studied dietary data provided from 3486 participants in the Whitehall II Study. With an average age of 55 years the participants, who worked in civil service departments in London, completed a questionnaire on their eating habits at the start of the trial and, five years later, a self-assessment on depression.
The team, led by Archana Singh-Manoux, identified two dietary patterns. Those with the highest intake of whole foods, such as fruits, vegetables and fish, were less likely to report depression symptoms later on.
Those eating a lot of processed meat, chocolate, sweetened desserts, fried foods, refined cereals and high fat dairy, on the other hand, were seen to be more vulnerable to depression.
The clear distinction remained even after the researchers had accounted for factors like smoking, level of physical activity, and body mass.
The researchers do note certain limitations in the study. For instance, the participants were mostly white, office-based civil servants who were not representative of the general population. Moreover, the questionnaire method only covered specific foods and is less reliable than the diary method of collecting dietary data.
They looked to test whether existing depression could be leading to certain dietary habits using the GHQ depression subscale and dietary patterns assessed 6 years later. No significant association was found.
While there is need for more research on the link, the researchers proposed several possible mechanisms for the observation.
One suggestion was that the high folate content in certain cruciferous and leafy vegetables and dried legumes could play a role, since previous studies have suggested lack of folate could affect brain chemistry.
Another suggestion is that high fish intake could reduce depression incidence, due to the omega-3 fatty acids present in fish oil. Antioxidants in fruit, too, could play a role – or, indeed, the effect could be down to the cumulative effect of several nutrients in the diet as a whole, not one in particular.
There is also a chance that the effect could be down to heart disease and inflammation, since some research has linked these conditions, which are aggravated by the highly processed Western way of eating, to depression.
The British Journal of Psychiatry (2009), 195, 408-413
Dietary pattern and depressive symptoms in middle age
Akbaraly, T; Brunner, E; Ferrie, J; Marmot, M; Kivimaki, M; Singh-Maoux, A.