This study assessed the anti-inflammatory status of the diet using a recently established and validated Dietary Inflammatory Index (DII). The DII (2) was developed following review of almost 2,000 scientific articles citing the response of six inflammatory markers to food nutrients. Foods that are generally considered “healthy,” such as fish, yoghurt, pulses, pasta, vegetables, fruit and wine are also associated with lower concentrations of these inflammatory biomarkers for people who consume them. Identified anti-inflammatory components included marine omega-3 fatty acids, vitamins B1, B2, B3 and folic acid, vitamin A, vitamin C, vitamin E, beta-carotene, magnesium and zinc.
The DII methodology was used in 2015 with a cohort in Spain. It demonstrated a significant dose response effect with regard to the DII scores and depression (3).
A recent meta-analysis (4) of randomised controlled trials (RCTs) that used an intervention of marine omega-3 fatty acids in patients with depression conducted over the last 35 years on more than 10,000 patients clearly demonstrated clinical benefits with regard to ameliorating the depressive symptoms in patients with diagnosed, pre-existing depression. However, the study also demonstrated that the eicosapentaenoic acid (EPA): docosahexaenoic acid (DHA) ratio had to be EPA rich for the positive effects to occur.
While an association between inflammatory status and depression has been noted in previous studies, the mechanism has yet to be established. It has been suggested that metabolic changes due to insulin resistance or hyperleptinaemia, which often occur with such conditions as obesity, type 2 diabetes and metabolic syndrome may be the cause (5). It has been observed that obese adults have higher circulating levels of cortisol than healthy adults, which leads to increased reactivity to psychological stress (6).
The new study by Shivappa et al. (1) measured the DII in a cohort of 6,438 Australian women (average age 52 years) over a 12-year period. They found that that the quartile of women with the lowest DII indexes were around 20 percent less likely to develop depressive symptom when compared with the highest quartile. The study clearly establishes that a healthy diet is good for the mental health as well as physical health.