According to the World Health Organization, depression is a leading cause of disability worldwide and a major contributor to the overall global burden of disease. Globally, more than 264 million people of all ages suffer from depression.[i] The standard treatment for depression is antidepressants but 40 to 70% of patients are not alleviated by existing treatments.[ii] What if our diet could alleviate our moods?
Most of us have noticed that certain foods make us feel better while others leave us feeling tired, or simply do not seem to agree with our system. This connection between what we eat and how we feel is not just ‘in our head’! Food is such an important component of mental health that an entire field of medicine called nutritional psychiatry is dedicated to it.
Several studies also support the notion that there is a link between our diet and our emotional well-being, especially our risk of depression. For example, a recent meta-analysis conducted in 2016 and published in Psychiatry Research reviewed the results of 21 studies originating from 10 countries. The researchers concluded that a dietary pattern characterized by a high intake of fruit, vegetables, whole grain, fish, olive oil, low-fat dairy and antioxidants and low intakes of animal foods was associated with a decreased risk of depression. A dietary pattern characterized by a high consumption of red and/or processed meat, refined grains, sweets, high-fat dairy products, butter, potatoes and high-fat gravy, and low intakes of fruits and vegetables is associated with an increased risk of depression. The results of this research confirm what many have been advocating for a long time! Healthy eating patterns such as the Mediterranean diet could decrease the risk of depression while the highly criticized western style diet may increase the odds of suffering from it.[iii]
Since we tend to turn towards comfort foods when we feel depressed, researchers also investigated the possibility that depression came before diet in this vicious circle of poor eating patterns and poor emotional health. To find out if depression came before diet, researchers used a prospective study, in which they looked at baseline diet and then evaluated the incidence of depression/depressive symptoms in the participants in 24 independent cohorts totalling nearly two million people. They also concluded that adherence to a high-quality diet was associated with a lower risk of depressive symptoms over time.[iv] This study also highlighted that a relatively low dietary inflammatory index was also associated with a somewhat lower incidence of depressive symptoms. The link between inflammation and depression is even more solid for patients who do not respond to current antidepressants.[v] The high-quality diets mentioned in studies usually involved good fats consumption, including omega-3 fatty acids from fish. Several meta-analyses have reported positive outcomes for omega-3 fatty acid treatment of depression, which may in part explain the benefits associated to this type of diet.[vi]
The high intake of fruit and vegetables provide antioxidants but also dietary fibre. Fibre is a crucial component of a healthy diet, with benefits that can be attributed to processes in the gut microbiota. Observational studies support associations between dietary fibre intake and depression and inflammation. A recent review published in May proposes that fibre reduce inflammation in the gut and could modify microbiota-driven gene expression and increase production of neurotransmitters.[vii]
The relatively new science of epigenetics widens our horizons regarding the potential benefits associated with a healthy diet and lifestyle. Although this science is still in its infancy and we are far from having all the answers, we do not need to wait to understand all the mechanisms to adopt a healthy diet such as the Mediterranean diet. The benefits of a diet rich in antioxidants, fibre and good fats and low in processed, pro-inflammatory foods will benefit not only our emotional well-being but also all chronic diseases such as cardiovascular diseases, diabetes and cognitive disorders.
[ii] Krishnan V, Nestler EJ. The molecular neurobiology of depression. Nature. 2008;455(7215):894-902. doi:10.1038/nature07455 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721780/
[iii] Li Y, Lv MR, Wei YJ, et al. Dietary patterns and depression risk: A meta-analysis. Psychiatry Res. 2017;253:373-382. doi:10.1016/j.psychres.2017.04.020 https://www.sciencedirect.com/science/article/abs/pii/S0165178117301981
[iv] Molendijk M, Molero P, Ortuño Sánchez-Pedreño F, Van der Does W, Angel Martínez-González M. Diet quality and depression risk: A systematic review and dose-response meta-analysis of prospective studies. J Affect Disord. 2018;226:346-354. doi:10.1016/j.jad.2017.09.022 https://pubmed.ncbi.nlm.nih.gov/29031185/
[v] Krishnan V, Nestler EJ. The molecular neurobiology of depression. Nature. 2008;455(7215):894-902. doi:10.1038/nature07455 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721780/
[vi] Lin PY, Mischoulon D, Freeman MP, et al. Are omega-3 fatty acids antidepressants or just mood-improving agents? The effect depends upon diagnosis, supplement preparation, and severity of depression. Mol Psychiatry. 2012;17(12):1161-1167. doi:10.1038/mp.2012.111 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3504139/
[vii] Swann OG, Kilpatrick M, Breslin M, Oddy WH. Dietary fiber and its associations with depression and inflammation. Nutr Rev. 2020;78(5):394-411. doi:10.1093/nutrit/nuz072 https://pubmed.ncbi.nlm.nih.gov/31750916/