A connection between the gut microbiome and psychological phenomena has long been suggested. In their landmark studies, Thaiss et al. (2016a, 2016b) displayed the role of persistent gut microbiome alterations on post-dieting weight gain as well as diurnal rhythmicity. Probiotic supplements ar a new trend, but the composition of the gut microbiome is complex, as is the composition of the products. Now, a team around assistant professor Dr. Premsyl Berick at McMaster University in Canada tracked down bifidobacterium longum as one major candidate in mediating the gut-brain connection (Pinto-Sanchez et al., 2017).
In a cohort of 22 individuals with IBS symptoms, bifidobacterium longum supplementation lead to a 2 point decrease in depression inventory scores against no change in 22 controls on placebo. The patients were shown to respond less to negative environmental stimuli compared to the placebo group in fMRI scans of amygdala and other relevant brain centers. Whereas depression scores were reduced, no effect on anxiety was found. The improvements were attributed to a reduction in limbic reactivity.
Unfortunately, the original article is behind a paywall.
Pinto-Sanchez, M. I., Hall, G. B., Ghajar, K., Nardelli, A., Bolino, C., Lau, J. T., & … Bercik, P. (2017). Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: a Pilot Study in Patients With Irritable Bowel Syndrome. Gastroenterology, doi:10.1053/j.gastro.2017.05.003
Thaiss, C. A., Itav, S., Rothschild, D., Meijer, M., Levy, M. Moresi, C., & … Elinav, E. (2016a). Persistent microbiome alterations modulate the rate of post-dieting weight regain. Nature. Advance online publication. Retrieved Dec 01, 2016 from http://www.nature.com/nature/journal/vaap/ncurrent/full/nature20796.html (via University of Liverpool). doi:10.1038/nature20796
Thaiss, C., Levy, M., Korem, T., Dohnalová, L., Shapiro, H., Jaitin, D., & … Elinav, E. (2016b). Microbiota Diurnal Rhythmicity Programs Host Transcriptome Oscillations. Cell, 167, 1495-1510.e12. doi:10.1016/j.cell.2016.11.003