Mariam KhayretdinovaJuly 14, 2021 - 5 min read
Depression and Nutrition
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While pre-existing depression may influence poor food choices, at least one study utilizing participants’ baseline diet as the independent variable found that consuming a healthy diet (for example, Mediterranean) correlated with a lower risk of future depression (Tello, 2020).
A study of dietary patterns and depression risk in ten countries found that the typical Western diet is related to increased depression risk. These foods include red meat, processed meat, refined grains, sugary foods, high-fat dairy products, potatoes, high-fat gravy, and limited consumption of fruits and vegetables. Conversely, diets containing fruit, vegetables, whole grains, fish, olive oil, low fat dairy, antioxidants, and limited quantities of animal products correlated with decreased depression risk (Li et al., 2017). A more recent study has corroborated evidence that poor diet including processed foods and sweets correlated with increased depression symptom report, while people consuming fruit, vegetables, and fish correlate with reduced incidence of depression (Zeratsky, 2018).
Interestingly, gut bacteria can influence food choices, and dietary choices impact which gut bacteria thrive (Madison & Kiecolt-Glaser, 2019). These factors in turn influence mental health in a cyclical feedback loop. Depressed mood and stress can increase likelihood of consuming comfort foods, typically highly processed products high in refined sugars and unhealthy fats. These eating patterns select for certain types of bacteria that thrive on these nutrients.
Stress and depression can also change which bacteria are prevalent in the gut through hormones, inflammation, and changes in the autonomic nervous system. These biological processes result in the bacteria releasing chemicals that resemble human hunger hormones and thereby influence mood and eating (Madison & Kiecolt-Glaser, 2019). Notably, inflammation is a key factor linking other risk factors for depression, including neurotransmitter imbalance, childhood trauma, and stress. Gut bacteria may represent one means of intervention by regulating chronic inflammation in patients with depressive symptoms (Koopman & El Aidy, 2017). A review of the literature found that diet quality and gut microbiota are connected to mental health through regulation of metabolic pathways, reducing inflammation, reducing cell death and supporting neuron growth (Mörkl et al., 2018).
There are also some other ways eating habits directly influence mood through a biological pathway. Macronutrients play a specific role in moderating depression (Rao et al., 2008). For example, carbohydrates impact mood through the metabolic pathway. Insulin is released following consumption of carbohydrates, which in turn triggers tryptophan in the brain, which modulates neurotransmitter levels. While diets deficient in carbohydrates may precede depressive episodes, a diet high in foods with a low glycemic index moderates brain chemistry more effectively over the long term. In comparison, processed foods and simple carbohydrates may offer immediate improvement to mood but present few benefits in stabilizing it over the long term (Rao et al., 2008). Dietary fiber has demonstrated relationships with depression and inflammation. Proposed mechanisms of action include increased fiber resulting in gut bacteria modifying gene expression as well as neurotransmitter concentration, and fiber resulting in reduced inflammation by altering pH and reducing gut permeability (Swann et al., 2020).
Micronutrients such as tryptophan and omega 3 may be beneficial in treating depression as an adjunctive measure through dietary supplementation (Harbottle & Schofelder, 2008). Additionally, micronutrients are necessary for the body to produce neurotransmitters, and a shortage of neurotransmitters has been implicated in depression.
Many of these key nutrients, including amino acids, minerals, and B vitamins, are found in foods that make up parts of the Mediterranean diet (Popa & Ladea, 2012). Magnesium intake was found to be associated with reduced risk of depression; however, this finding was relevant for women of all age groups but not for men (Sun et al., 2019). A systematic review found that zinc supplementation may be helpful in improving symptoms for people diagnosed with major depression who are also receiving antidepressant treatment (da Silva, 2021). In a review of the literature, supplementation with vitamin D, vitamin C, zinc and iron reduced depressive symptoms, while folate produced mixed results. Reduced serum levels of iron, calcium, manganese, potassium, vitamin D, vitamin E, zinc, vitamin B-6, folate, vitamin B-12, and vitamin C correlated with the presence of depressive symptoms (Campisi et al., 2020).
Several plant compounds have shown effectiveness in reducing depressive symptomatology (Nabavi et al., 2015). Green tea catechins and anthocyanins decreased symptoms of depression through interfering with monoamine oxidase which is responsible for breaking down neurotransmitters that influence mood. Procyanidins found in cocoa also reduced depressive symptoms. Resveratrol, commonly associated with red wine, inhibited reuptake of serotonin and noradrenaline. However, these compounds and their effects on depression have been studied primarily in animals. Additional research would be helpful in determining effectiveness of these compounds in attenuating depression in human subjects (Nabavi et al., 2015).
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Koopman, M., & El Aidy, S. (2017). Depressed gut? The microbiota-diet-inflammation trialogue in depression. Current Opinion in Psychiatry, 30(5), 369-377. https://doi.org/10.1097/YCO.0000000000000350
Li, Y., Lv, M. R., Wei, Y. J., Sun, L., Zhang, J. X., Zhang, H. G., & Li, B. (2017). Dietary patterns and depression risk: A meta-analysis. Psychiatry Research, 253, 373–382. https://doi.org/10.1016/j.psychres.2017.04.020
Madison, A., & Kiecolt-Glaser, J. K. (2019). Stress, depression, diet, and the gut microbiota: human-bacteria interactions at the core of psychoneuroimmunology and nutrition. Current Opinion in Behavioral Sciences, 28, 105–110. https://doi.org/10.1016/j.cobeha.2019.01.011
Mörkl, S., Wagner-Skacel, J., Lahousen, T., Lackner, S., Holasek, S. J., Bengesser, S. A., Painold, A., Holl, A. K., & Reininghaus, E. (2018). The role of nutrition and the gut-brain axis in psychiatry: A review of the literature. Neuropsychobiology, 1–9. Advance online publication. https://doi.org/10.1159/000492834
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Popa, T. A., & Ladea, M. (2012). Nutrition and depression at the forefront of progress. Journal of Medicine and Life, 5(4), 414–419.
Rao, T. S., Asha, M. R., Ramesh, B. N., & Rao, K. S. (2008). Understanding nutrition, depression and mental illnesses. Indian Journal of Psychiatry, 50(2), 77–82. https://doi.org/10.4103/0019-5545.42391
Sun, C., Wang, R., Li, Z., & Zhang, D. (2019). Dietary magnesium intake and risk of depression. Journal of Affective Disorders, 246, 627–632. https://doi.org/10.1016/j.jad.2018.12.114
Swann, O. G., Kilpatrick, M., Breslin, M., & Oddy, W. H. (2020). Dietary fiber and its associations with depression and inflammation. Nutrition Reviews, 78(5), 394–411. https://doi.org/10.1093/nutrit/nuz072
Tello, M. (2020). Diet and depression. Harvard Health Blog. https://www.health.harvard.edu/blog/diet-and-depression-2018022213309
Zeratsky, K. (2018). Junk food blues: Are depression and diet related? https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/depression-and-diet/faq-20058241