The notion that “we are what we eat” is not a new concept. In fact, for centuries people have studied the impact food has on health. The problem, however, is that much of the research has focused on the implications for physical health. That is, noncommunicable disease, such as obesity, type II diabetes, hypertension, cardiovascular disease, and various forms of cancer have been the primary focus when it comes to food and health6. Unfortunately, mental health problems, such as depression, are also widespread and require further attention from the medical and health communities in regards to how food impacts mood.
In the 17th century Rene Descartes suggested that the mind functioned independent of the body. Research in the 20th century has refuted that idea and found that the mind is in fact closely related to the body in a bidirectional relationship between the central nervous system and the endocrine and immune systems5. These finding have led researchers to determine that depression, and its various subtypes, are grounded in biological processes including: inflammation, oxidative processes, and brain plasticity and function6. Given that diet and nutrition can alter such processes, recent studies have begun to look at the effect, both positive and negative, that these can have on depression.
Inflammation can be a key determinant in both the onset and continuance of depression6. In fact, depression in the older population is correlated with higher levels of inflammation8. Although inflammation is generally associated with some form of injury or infection, a growing body of information demonstrates that dietary patterns can affect the immune system, and thus cause inflammation, in turn making depression a chronic inflammatory condition5. Depression is linked to an upregulated inflammatory response, however, a Mediterranean diet consisting of fruit, vegetables, fish, and olive oil has been shown to decrease various inflammatory markers due to the anti-inflammatory components of antioxidants8. A Spanish longitudinal study looked at the Mediterranean diet and depression rates and found that less than 5% of the 10,094 adults studied reported a new depression diagnosis after several years. Interestingly, lower compliance to the Mediterranean diet dramatically increased the likelihood of becoming depressed1.
On the other hand, Western diets, consisting of processed foods and refined carbohydrates, increase levels of pro-inflammatory C-reactive proteins6. A study done in the United Kingdom compared the depression rates of those whose diet was comprised of mainly whole foods or processed foods. It found that whole foods offered a protective effect in regard to depression and that those who ate the most whole foods reported the fewest depressive symptoms2. One explanation for this is that colorful fruits and vegetables, spices, such as turmeric, and green tea contain polyphenols, which are strong antioxidants and anti-inflammatories4.
Depression, and its relative illnesses, is influenced by various oxidative processes. That is, oxidative stress contributes to the pathophysiology of depression6. When a person overeats, they consume too many calories for the body to be able to handle. In turn, this bombards the brain with oxidative insult, leaving it vulnerable to illness4. This oxidative damage to be associated with several psychiatric conditions, including bipolar disorder and depression due to the neuronal damage, intracellular signaling disruption, and eventual neuronal death5.
In order to decrease or prevent neuronal death from taking place, it is imperative for antioxidant rich foods to be consumed. Many fruits and vegetables are high in antioxidants. Specifically, goji berries, apples, blueberries, spinach, strawberries, and grapes are excellent sources5. In addition, vitamins C and E also have an antioxidant effect. A food’s Oxygen Radical Absorbance Capacity (ORAC) score is one way to determine its antioxidant level. The higher the score, the more potent its antioxidant level. Cloves, cinnamon, turmeric, acai berries, blueberries, plums, broccoli, red leaf lettuce, asparagus, pecans, walnuts, dark chocolate, and garlic have some of the highest ORAC scored foods11. Because these foods are high in antioxidants, they are able to reduce the levels and impact of oxidative stress to the brain, thereby decreasing the likelihood of depressive symptoms being experienced6. Our family drinks this daily as it packs a powerful antioxidant punch. It has the antioxidant equivalent to 814 blueberries!
Brain plasticity and function are also factors related to depression. This is especially true in important developmental stages. Dietary habits during these periods influence the likelihood of depression by impacting brain development and plasticity and altering gene expression7. Proper nutrition is imperative for the brain to grow and function, as well as brain derived neurotrophic factor (BDNF), which is a major component in depression and its subtypes7. Several animal studies have demonstrated diets high in unhealthy fat are associated with lower BDNF levels and lower neuronal plasticity, while those rich in omega-3 fatty acids, vitamin E, or flavonols are linked with high production of BDNF10. In fact, studies have found that depressed individuals who ate a Mediterranean diet increased their BDNF levels, and those who had a Mediterranean diet with nuts had even higher levels10. Further studies have found that increased consumption of unhealthy and processed foods are correlated with higher levels of self-reported depression in adolescents, and that a link exists between diet quality and depression levels in both adolescents and adults7.
Omega-3 fatty acids not only increase BDNF production, they also offer a protective factor from depression and suicide9. People whose cholesterol levels are low due to an insufficient amount of omega-3 being ingested, are drastically more at risk of developing depression3. Countries that consume fish as a dietary staple, such as Japan and Taiwan, have 10 times lower depression rates than North America9. To increase omega-3 intake, eat salmon, tuna, fish oil, or flaxseed oil.
It is clear that ingesting unhealthy and/or processed food and abstaining from nutrient dense quality food is correlated with higher depression rates and depressive symptoms. This is likely due to the innate connection between the body and the mind. Research indicates this has to do with biological issues, such as inflammation, oxidative processes, and brain plasticity and function, which are altered due to diet quality and nutrient intake6. Being able to determine precisely which foods positively and negatively affect depression, and its various forms, has the potential to dramatically change both the number of people suffering from this illness and the way in which it is treated. Food is a modifiable variable in most peoples’ lives, and is essential to survival. Therefore, the necessary time, effort, and resources should be spent better understanding the connection between food and mood.
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2. Davidson, K.M., & Kaplan, B.J. (2012). Food intake and blood cholesterol levels of community-based adults with mood disorders. BMC Psychiatry, 12(12), 1-8. Retrieved February 01, 2013 from ProQuest database.
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4. Gomez-Pinilla, F., & Nguyen, T.J. (2012). Natural mood foods: The actions of polyphenols against psychiatric and cognitive disorders. Nutritional Neuroscience, 15(3), 127-132. Retrieved January 19, 2013 from ProQuest database.
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10. Sanchez-Villegas, A., Galbete, C., Martinez-Gonzalez, M.A., Martinez, A., Razquin, C., Salas-Salvado, J. …Marti, A. (2011). The effect if the Mediterranean diet on plasma brain-derived neurotrophic factor (BNDF) levels: The PERDIMED-
NAVARRA randomized trial. Nutritional Neuroscience, 14(5), 195-201. Retrieved February 03, 2013 from ProQuest database.
11. Turner, J. (2011). Your brain on food: A nutrient-rich diet can protect cognitive health. Journal of the American Society on Aging, 35(2), 99-105. Retrieved January 19, 2013 from ProQuest database.