The Whitehall II Study is a large, longitudinal study following the health and wellness of over 10,000 British civil servants between the ages of 35 and 80. Recruitment started in 1985 and follow-up is ongoing. Whilst the study primarily releases data on the relationship between physical health and socioeconomic status the enormous amount of data collected is often shared with and analysed by international researchers interested in other aspects of health and lifestyle. A paper published in Clinical Psychological Science reviewed the Whitehall data looking at the relationship between diet and depression. They were curious as to whether the inflammatory potential of a person’s diet had any bearing on their risk of developing the illness.

Inflammation is they way that the body responds to physical illness and injury and is also associated with lifestyle factors such as chronic stress and poor diet. The Dietary Inflammatory Index (DII) is a reliable assessment of how likely certain foods are to promote inflammation in the body. Broadly, processed foods increase inflammation while whole foods, fruits, vegetables, nuts and oily fish reduce it. A higher score on the DII is linked to higher markers of inflammation in the body.

In this analysis the researchers looked at the available dietary information and depression status of 4246 people over a period of five years. They were interested in what they have called ‘recurrent depression’ - people who had depression at the start and again at the end of this five-year period. (They did not look at whether the depression was ongoing during this period or whether it had gone in to remission at any point.) Alongside diet they looked at other health-related factors such as level of exercise, smoking status, alcohol consumption, obesity, heart disease, diabetes and stroke.

The researchers found that women with high scores on the Dietary Inflammatory Index were significantly much more likely to develop recurrent depression, and this effect was independent of other health factors. This is similar to the results of the large Spanish 'SUN Project' that showed that healthy (anti-inflammatory) diets were linked to a reduced risk of depression in men and women. The authors comment that these results support the growing body of research in to the relationship between diet, inflammation and depression.

Reference

Akbaraly, T. N., Kerlau, C., Wyart, M., Chevallier, N., Ndiaye, L., Schivappa, N., Hébert, J. R., Kivimäki, M. (2016). Dietary Inflammatory Index and Recurrence of Depressive Symptoms: Results From the Whitehall II Study. Clinical Psychological Science, first published on August 8, 2016 doi:10.1177/2167702616645777