The gut microbiome has an intriguing relationship to mental health. Communication along the gut-brain axis is strongly implicated in depression and anxiety in animal models.
Attempts to replicate rodent study outcomes in humans are encouraging. In one study, a strain of bifidobacterium which was able to normalize anxiety-like behavior in mice went on to show positive outcomes in humans with irritable bowel syndrome – linked depression. The improvements were related to changes in brain activation patterns indicating that this strain of probiotic may reduce limbic reactivity.
Data from the Belgian Flemish Gut Flora Project
Now new data using a large human group has strengthened that link in depression and quality of life in general.
Jeroen Raes at the Catholic University of Leuven, Belgium, and his colleagues analyzed evidence from the Belgian Flemish Gut Flora Project.
In this 1000+ cohort, the team showed that two bacterial species were positively correlated with self-reported high quality of life, whereas a third was most abundant in people reporting low quality of life.
Faecalibacterium and Coprococcus bacteria were linked with higher quality of life indicators. These two are butyrate-producing. Amidst the cluster of short-chain fatty acids (SCFAs), butyrate is a stand-out. This has lead researchers to try to define its benefit in diseases.
People with depression in the cohort more often had a type associated with low overall bacterial abundance. Dialister and Coprococcus spp. were depleted in depression.
Also of interest is the catalogue of neuroactive potential of sequenced gut prokaryotes constructed by the researchers. The neuroactive potential of the human gut microbiota in quality of life and depression appeared in Nature Microbiology.
Data from the Korean National Health and Nutrition Examination Survey
And this from prior IPA reporting: A nationwide, large population-based database among more than 26,000 Korean adults and using the Korean National Health and Nutrition Examination Survey (KNHANES, 2012–2016) data found that intake of probiotic food is significantly associated with lower severity and prevalence of depressive symptoms measured by a PHQ-9 questionnaire.
Probiotic food consumption is associated with lower severity and prevalence of depression: A nationwide cross-sectional study appeared in Nutrition journal in 2019.
Gregor Reid of Lawson Health Research Institute in Canada gives another angle in last year’s Disentangling What We Know About Microbes and Mental Health in Frontiers in Endocrinology.
“The possibility that vast numbers of microbes in the intestinal tract with the potential to produce compounds that include neurochemicals can influence the brain is compelling.”