Nutritional Pearls: Inflammation and Depression

Jean is a 20-year-old college student struggling with depression. She tells you that the majority of her diet consists of the food provided to her through her school’s meal plan, including hamburgers, pizza, fried chicken, and macaroni. She asks if a change in diet could benefit her depression.

How would you advise your patient?
(Answer and discussion on next page)

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Answer: A healthier diet may be a useful tool in your patients' arsenal to fight depression.

Research in both adults and children has linked eating more fast food to a greater risk of depression. We've also seen that a higher adherence to a Mediterranean-style diet is associated with better quality of life in general, both physically and emotionally, as well as an improved overall mood.

These are all studies that show only association, however, and we don't know why this might be. Today's research article, published last month in the British Journal of Nutrition suggests one explanation: an inflammatory diet.
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The Research

The authors made use of data gathered for the Australian Longitudinal Study on Women's Health, an on-going, long-term, large-scale study of Australian women that started in 1996. At the start of the study the participants were asked for demographic information such as age, education level, and marital status, as well as overall health information such as menopausal status, whether they smoked, and their height and weight. Other specialized questionnaires included a test known as the CESD-10 (Center for Epidemiologic Studies Depression-10), a 10-question depression screening test that measures depressive symptoms on a scale of 0 to 30, with scores of 10 or over indicating depression.

Detailed dietary questionnaires created specifically for Australians were added to the surveys in 2001, after which the participants were surveyed four additional times until 2013, the chosen endpoint for this study.

Rather than looking at specific elements of the participants' diets, such as vegetable intake, red meat, or even the amount of omega-3 fatty acids they consumed, the authors utilized a tool called the Dietary Inflammatory Index (DII). The authors describe the development of this tool as follows: "Developing the DII involved reviewing and scoring nearly 2000 scientific articles representing cell culture and laboratory animal experiments, as well as a variety of human studies on diet and six inflammatory markers (ie, C-reactive protein, IL-1b, IL-4, IL-6, IL-10, TNF-α)." With that tool, they were able to analyze each of the over 6400 participating women's diets and assign them an individual DII score, with positive scores meaning a pro-inflammatory diet and negative scores an anti-inflammatory diet.

The Results

After considering such variables as demographics, menopausal status, experience of major personal illness or injury, smoking status, body mass index, and even whether they had been diagnosed with or treated for depression, the authors found that those with the most pro-inflammatory diets were 19% more likely to develop depression than those with the most anti-inflammatory diets. The authors note that this was true even when those with the anti-inflammatory diets ate more red meat (something generally held to be pro-inflammatory) than those with the most pro-inflammatory diets overall—making it more likely that overall diet was responsible for the effects rather than a single food group.

What’s the “Take-Home”?

You're no doubt aware that depression is a complex issue that should not be reduced to "eat more vegetables" or "get more exercise" or even "eat an anti-inflammatory diet." This does suggest, however, that a healthier diet may be a useful tool in your patients' arsenal to fight depression. We know that a typical Western-style diet is pro-inflammatory and that a Mediterranean-style diet is anti-inflammatory (broadly speaking). In addition to considering a referral to a psychiatrist, recommend to your depressed patients that self-care should include a healthy diet of plenty of fruits, nuts, and vegetables; whole grains; less but leaner meats; delicious, fatty fish; dairy products like cheese and yogurt; legumes like lentils, beans, and peas; great monounsaturated fats like olive oil for cooking; and only moderate intake of alcohol, especially with meals.

Reference:

Shivappa N, Schoenaker DAJM, Herbert JR, Mishra GT. Association between inflammatory potential of diet and risk of depression in middle-aged women: the Australian Longitudinal Study on Women’s Health. Nutrition. 2016;16:1077-1086.