Relationship between diet, gut flora and depression

Link gut flora composition and depression

Article received from Natura Foundation, April 2019

This large-scale study investigated how bacterial strains in the gut can affect the quality of life of the host, humans. Butyrate-producing bacteria were associated with fewer depressive symptoms. 

So far, the two-way communication between the gut microbiome and the brain has mostly been studied in animal models, while research among humans has lagged behind. The FLemish Gut Flora Project (n=1,054) at the University of Leuven investigated how gut flora correlates with quality of life and depressive symptoms in the host. The results were published in Nature Microbiology.

In this study, the presence of Faecalibacterium- and Coprococcus-species consistently associated with higher quality of life. These bacteria produce butyrate (butyric acid). A lack of butyrate has been linked to depression before. In this study, the Coprococcus-species in depression depleted, even if the confounding effects of antidepressants were included.

 
The analysis identified the ability of the dopamine metabolite 3,4-dihydroxyphenyl acetic acid to positively correlate with mental quality of life and pointed to a potential role of GABA (gamma-aminobutyric acid). The scientists indicate that the results of this study - conducted at the population level in humans - prove that our microbiome is linked to mental health.

Role of anti- and pro-inflammatory foods 

Another large-scale meta-analysis reveals the association between diet and depressive feelings: people with pro-inflammatory eating habits were found to be 40% more likely to develop depression, compared with those with anti-inflammatory eating styles.

 
Pro-inflammatory foods are rich in glucose and saturated fatty acids, which can activate the immune system resulting in low-grade inflammation, leading to depression, among other things.

 
A Mediterranean diet rich in fibre, unsaturated fatty acids, vitamins and minerals, among others, is actually anti-inflammatory. The fibre is an important food source for the colon bacteria, which convert the fibre into butyric acid. This, among other things, has the positive effects, as revealed by research discussed in this article.

Source

Valles-Colomer, M. et al, The neuroactive potential of the human gut microbiota in quality of life and depression, Nature Microbiology, April 2019, p. 623-632. doi: 10.1038/s41564-018-0337-x, epub 2019 Feb 4, https://www.ncbi.nlm.nih.gov/pubmed/30718848