Depression and bipolarity are serious mental health disorders that are relatively common and sometimes associated to suicidal thoughts. The former affects more than one person out of five at least once in their lifetime. The latter, difficult to diagnose, affects 1 to 2.5% of people. Both diseases could be related to a gut dysbiosis which is sometimes correlated to the severity of the symptoms.
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It manifests itself by unusual sadness, loss of interest, inability to perform daily tasks, greater fatigue and is accompanied by an increase of cortisol levels22, and thus a disruption of stress response.
In animals, the absence of gut microbiota(or its disruption) is associated to depressive symptoms and to an imbalance of neurotransmitters (serotonin, dopamine, GABA...). Furthermore, inflammation-inducing molecules that are present in excess in the blood and produced by gut bacteria, seem directly related to the development of depression23. Although there are few, studies made in humans seem to have brought to light a bacterial signature: very recently, researchers discovered for instance that low levels of some bacterial genera in the intestines (Coprococcus and Faecalibacterium) are related to a feeling of poor quality of life in depressed patients.
Balanced gut, balanced mind
The administration of some psychobiotics, such as Lactobacillus and Bifidobacteria (bacteria from the Firmicutes phylum that are present at low levels in affected people) could be beneficial and be used as a supplement to antidepressant and anxiolytic treatments currently used. Initial results are encouraging: prolonged use can relieve depressive symptoms and psychological distress, without causing adverse events24.
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It would seem that high-glucose transformed products could increase predisposition to depression. In depressed patients, prebiotics (mainly galacto-oligosaccharides found in red beans, chickpeas, artichokes...) could act positively by stimulating the increase of bifidobacteria25. Opting for fruits, vegetables, fish (rich in omega-3 fatty acids) could restore the microbiota, regulate pro-inflammatory processes, and thus favorably impact mood. Turmeric could decrease cortisol levels in the saliva and increase gut flora diversity, resulting in positive effects on the state of mind and behavior
23 Hayley S, Audet MC, Anisman H. Inflammation and the microbiome: implications for depressive disorders. Current Opinion in Pharmacology, 2016
24 Vlainić JV, Šuran J, Vlainić T, Vukorep AL. Probiotics as an Adjuvant Therapy in Major Depressive Disorder. Curr Neuropharmacol. 2016;14(8):952-958
25 Dinan TG, et al. Feeding melancholic microbes: MyNewGut recommendations on diet and mood. Clin Nutr. 2018 Nov 17