Brain Awakening: Improve Cognitive Function Through Improving the Microbiome

Emerging research suggests that restoring certain beneficial bacteria can alleviate symptoms of mood disorders. This is due to the fact that the microbial communities of the gut are involved in a complex communication pathway between the gut and the brain, known as the gut-brain axis or GBA (1). The vagus nerve is a key feature of the GBA which provides a direct route between dendritic cells of the bowels and the hippocampus of the brain. The hippocampus is indicated in depression and anxiety and is significantly smaller in depressed patients. Ongoing exposure to stress and inflammation can inhibit neural growth in this brain region, preventing recovery of psychological symptoms.

Gut microbiota can stimulate the production of hippocampal brain-derived neurotropic factor (BDNF), a neurochemical that induces a calming response in the brain (2). Results of a recent study published in Neurogastroenterology and Motility show that Bifidobacterium can significantly increase BDNF production in mice, thereby calming the HPA axis (1). An Austrian study published in 2016 in the Brain, Behavior, and Immunity journal found that mice treated with a single round of antibiotics showed measurable cognitive impairment compared to germ-free and control mice (3). BDNF expression is also known to be altered in germ-free mice as well as mice with antibiotic-induced gut dysbiosis, suggesting that a deficit in hippocampal BDNF may be partially responsible for the cognitive impairments seen with antibiotic usage.

While murine models provide great insight into the relationship between bacterial colonies and mental health, the benefits of oral probiotic supplementation in humans can be more difficult to assess. Bifidobacterium, for example, does not always survive digestion when taken as a supplement but can increase in population with synbiotics, or dual treatment with prebiotics and probiotics. Non-digestible oligosaccharides like galactooligosaccharide and xylooligosaccharide have both been shown to increase the abundance of Bifidobacterium by 67% and 21% respectively. (4,5) Furthermore, supplementing with a combination of oligosaccharides and Bacillus spores increased the population of Bifidobacterium by more than 140% in a human gut model study. (6)

References:

1. Clapp M, Aurora N, Herrera L, Bhatia M, Wilen E, Wakefield S. Gut microbiota’s effect on mental health: the gut-brain axis. Clinics and Practice. 2017;7(4). doi:10.4081/cp.2017.987.
2. Bercik P, Park AJ, Sinclair D, et al. The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut-brain communication. Neurogastroenterology & Motility. 2011;23(12):1132-1139. doi:10.1111/j.1365-2982.2011.01796.x.
3. Frolich EE, Farzi A, Maverhofer B, et al. Cognitive impairment by antibiotic-induced gut dysbiosis: Analysis of gut microbiota-brain communication. Brain Behav Immun. 2016;56:140-55. doi: 10.1016/j.bbi.2016.02.020.
4. Depeint F, et al. Prebiotic evaluation of a novel galactooligosaccharide mixture produced by the enzymatic activity of Bifidobacterium bifidum NCIMB 41171, in healthy humans: a randomized, double-blind, crossover, placebo-controlled intervention study 1–3. Am J Clin Nutr. 2008;87(3):785-91.
5. Finegold SM, et al. Xylooligosaccharide increases bifidobacteria but not lactobacilli in human gut microbiota. Food Funct. 2014;5(3):436-45.
6. Marzorati M, Van den Abbeele P, Duysburgh C, et al. Evaluation of the effects of four-week synbiotic administration on the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®). ProDigest Report. 2018:1-44.