There has been a long held belief that diet may influence well-being. The phrase “you are what you eat” suggests that nutrition has an impact on physical as well as mental health.  Until recently, however, there have been few studies that provide data to support this idea.

In a study published by the American Journal of Psychiatry this month, Jacka and colleagues looked at how overall diet patterns impact mental health. This is one of a few studies of its kind to go beyond examining the effect of individual nutrients on mood and general well-being.

Over one thousand women (ages 20-93) were followed over a 12-month period. They were given a comprehensive dietary questionnaire. Psychiatric disorders were assessed using the Structured Clinical Interview for DSM-IV-TR (SCID), focusing on depression and anxiety.  The General Health Questionnaire (GHQ-12) was also used.  Variables, such as education, physical activity, alcohol and tobacco use and body mass index, were also recorded.

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.

After adjusting for age, socioeconomic status, education, and health behaviors, Jacka and colleagues found that a traditional diet was associated with a lower risk of major depression, dysthymia, and anxiety disorders. A western diet was associated with higher GHQ-12 scores, reflecting higher levels of psychological morbidity.   There was also an inverse association between the quality of the diet and GHQ-12 score.

These findings suggest that a diet rich in processed food leads to higher rates of depressive illness. This has practical implications for our patients, suggesting that it may be prudent to provide nutritional information and interventions focused on incorporating “whole foods”. These are foods such as fruits, vegetables and fish. In an accompanying editorial, Dr. Marlene Freeman of the MGH Center for Women’s Mental Health notes, “It is both compelling and daunting to consider that dietary intervention at an individual or population level could reduce rates of psychiatric disorders. There are exciting implications for clinical care, public health, and research.”

In another study published in the Archives of General Psychiatry, Luppino and colleagues performed a meta-analysis of 15 studies looking longitudinally at the relationship between depression, overweight and obesity. Overweight is defined as a body mass index (BMI) of 25-29.9 and obesity as a BMI of > or = 30. They studied a total of 55,387 subjects, both men and women, in Europe and the USA.

They found that obese subjects had a 55% increased risk of being depressed and that depressed subjects had a 58% increased risk of being obese. They observed that the association was more pronounced among Americans than in Europeans.  The correlation between depression and obesity was stronger than the relationship between depression and overweight.  The authors noted that being overweight increased the risk of depression, however depression was not predictive of being overweight over time.

The data presented in this article is very timely, as the rates of obesity in the U.S. have reached an all time high. This study speaks to the importance of provider awareness of the association between obesity and mental health. This increased awareness could lead to early detection, concurrent treatment and eventual prevention of both conditions. Now, there is growing evidence that diet and nutrition has an impact on overall health, not only cardiovascular health, but mental health as well.

Maya Rydzewski, MD

Jacka FN, Pasco JA, Mykletun A, Williams LJ, Hodge AM, O’Reilly SL, Nicholson GC, Kotowicz MA, Berk M: Association of western and traditional diets with depression and anxiety in women. Am J Psychiatry 2010; 167:305–311

Marlene P. Freeman, MD: Nutrition and Psychiatry. Am J Psychiatry 2010:  167:244-247

Luppino FS, de Wit LM, Bouvy PF, Stijnen T, Cuijpers P, Penninx BW, Zitman FG. Overweight, Obesity and Depression: A Systematic and Meta-analysis of Longitudinal Studies. Arch Gen Psychiatry 2010; 67(3):220-229