The American Journal of Psychiatry has published a study that found that what we eat affects how we feel. The more than one thousand women studied answered a number of questionnaires and were followed for one year.
"Diets were divided into 3 types: 'western', which was characterized by processed meats, pizza, chips, beer and hamburgers; 'traditional', which included vegetables, beef, lamb and fish; and 'modern', which incorporated fruit, nuts, fish, tofu, beans, red wine and yogurt."
Women following a traditional diet featuring meats and vegetables showed lower incidence of depression. Results for the women on the western diet reflected that eating predominantly processed foods led to greater levels of depression. The healthier the diet, the less depression was a problem.
The study results suggest that the food people eat has a significant effect not only on physical health but also on mental health. It was concluded that more attention should be paid by health professionals to the foods people eat.
http://www.womensmentalhealth.org/posts/diet-and-nutrition-may-influence-risk-for-depression