How could diet affect depression?

It appears that a Mediterranean diet or a diet consisting of foods with a low Dietary Inflammatory Index (DII) has been associated with a reduced risk of depression.^[1] However, more research is needed before a specific diet can be recommended. With that being said, current research suggests that improving one's diet by replacing "junk" foods with nutrient-dense, higher fiber foods, such as vegetables, fruits, whole grains, and nuts reduce the risk and symptoms of depression.^[2]