People who eat a diet laden with processed and high-fat foods may put themselves at greater risk of depression, according to UCL research published today.
The research team, led by Tasnime Akbaraly (UCL Epidemiology and Public Health), also found that eating a ’whole food? diet with plenty of fresh vegetables, fruit and fish could help prevent the onset of depressive symptoms in middle age.
The study, published in the November issue of British Journal of Psychiatry, is the first to examine the association between overall diet and depression - previous studies have focused on the effect of individual nutrients.
Researchers from UCL studied 3,486 people with an average age of 55, and who worked in civil service departments in London. Each participant completed a questionnaire about their eating habits, and a self-report assessment for depression.
The researchers found that people with the highest intake of ’whole food? were less likely to report having symptoms of depression. In contrast, high consumption of processed food was associated with increased odds of depression.
These associations between diet and onset of depressive symptoms remained after the researchers controlled for other indicators of a healthy lifestyle, such as not smoking, taking physical activity and a healthy body mass.
The authors said: ‘Our results suggest that consuming fruits, vegetables and fish may afford protection against the onset of depressive symptoms, whereas a diet rich in processed meat, chocolates, sweetened desserts, fried food, refined cereals and high-fat dairy products would increase people’s vulnerability.’
The researchers put forward several explanations for their findings. Firstly, the high level of antioxidants in fruits and vegetables could have a protective effect, as previous studies have shown higher antioxidant levels to be associated with lower risk of depression. Folate, which is found in large amounts in vegetables such as broccoli, cabbage and spinach, and dried legumes such as lentils and chickpeas, may have a similar protective effect.
Secondly, eating lots of fish may protect against depression because of its high levels of long-chain polyunsaturated fatty acids, which are a major component of neuron membranes in the brain.
Thirdly, it is possible that a ’whole food? diet protects against depression because of the combined effect of consuming nutrients from lots of different types of food, rather than the effect of one single nutrient.
The researchers said that further research is needed to explain why eating processed food is associated with higher risk of depression, but they suggested it could be because a processed food diet is associated with a higher risk of coronary heart disease and inflammation, which are known to be involved in the development of depression.
The researchers concluded: ‘The deleterious effect of a processed food diet on depression is a novel finding. Our research suggests that healthy eating policies will generate additional benefits to health and well-being, and that improving people’s diet should be considered as a potential target for preventing depressive disorders.’