New research linking processed foods with increased depression in middle age adds to the plethora of evidence suggesting that food has a core role in preventing depressive illness. 
Researchers from University College, London, wanted to expand on the research looking at the link between food and depression, for which there are relatively few studies in comparison with those looking at the effects of the fish and vegetable-rich Mediterranean diet on age-related mental decline, including both Alzheimer’s and Parkinson’s disease.
Dietary data was taken from 3486 people in the civil service with an average age of 55 years, completing detailed questionnaires on their eating habits at the start of the trial, and then five years later a self-assessment on depression.
Perhaps unsurprisingly, those whose diets included a high intake of whole foods including fruit, vegetables, whole grains and fish, were less likely to report depression symptoms later on. Those more susceptible to depression reported a high intake of processed meat, chocolate, sweets, fried foods, refined grains and dairy.
The researchers acknowledged certain limitations of the study – in terms of the sample, the predominantly white civil servants are not representative of the general population, and the questionnaire only covered specific foods. Nevertheless, the researchers had accounted for factors such as smoking, physical activity and body mass.
Possible explanations for this outcome include the high levels of folate in cruciferous and leafy vegetables, beans and pulses, in line with studies which link low levels of folate with altered brain chemistry. The researchers also suggest that a high fish intake could affect one’s propensity to develop depression, due to the mood-stabilising effects of omega-3 fatty acids, particularly the long-chain omega-3 EPA (eicosapentaenoic acid). Similarly, antioxidants also have a role in mood, and it is likely a combination of these factors which affects risk.
Heart disease and inflammation may also be factors, since these are also linked with depression, and the highly processed diets favoured in the West.
Dr Nina Bailey comments, “Common retrospective methods such as 24-hour recall and food frequency questionnaires are extremely useful dietary assessment tools that give estimates of nutritional intakes that can then be correlated directly with disease risk. The link between diet and depression using data from such studies is giving a consistent message we need to change our dietary patterns, chuck in the junk food and go back to the basics of sourcing fresh unprocessed products and cooking from scratch.”
 Akbaraly, T; Brunner, E; Ferrie, J; Marmot, M; Kivimaki, M; Singh-Maoux, A. Dietary pattern and depressive symptoms in middle age, The British Journal of Psychiatry (2009), 195, 408-413.