Mind-altering microorganism? Microbiome & mood & behavior
The human gut resides trillions of symbiotic bacteria, which is almost 10 times greater than the total number of human cells. This community of bacteria has developed a mutualistic relationship with their host (human), and plays a crucial role in various functions in our body.
The first 1,000 days of a human’s life is critical for determining their unique gut environment for the rest of their life, starting from the vagina canal of how the babies are delivered, and may be altered throughout your life based on a variety of factors. Some empirical examples of this is stress, especially in early life can alter the microbial composition and will have an impact on physiology in adulthood.
In recent years, there are growing interests in what is known as the gut brain axis, which is the bidirectional pathway between the gut (gastrointestinal tract) and the brain through neural, endocrine and immune pathway. Though how exactly the mechanism of this communication is carried out is still not fully understood, but it has been suggested that the mechanism may involves immune activation, alteration in microbial composition, vagus nerve signaling, alterations in tryptophan metabolism, bacterial cell wall sugars and production of specific microbial neuroactive metabolites.
The mind alternating microbe-an evolutionary theory
Why would these microbes want to manipulate our behavior in the first place? Due to the unique symbiotic beneficial relationship of our brain and the gut, the symbiont(microbes)’s survival is heavily dependent on us; the host. From a natural selection standpoint, microbiome diversity is linked to fitness in mammals, there is an adaptive component to microbiome variation that functions to optimize food preferences, social behavior, immune function, stress responses and cognitive abilities that are mutually beneficial to the host and the microbe.
For example, the gut microbes depend fully on the host for nutrients that are necessary for their growth. Gut microbiome can modulate your feeding pattern, they have intrinsic ability to regulate their growth and maintain their own population within the gut, and can interfere with molecular pathway controlling feed pattern of the host. Studies suggest that bacterial components and metabolites can stimulate intestinal satiety pathways, their production depends on bacterial growth cycles. Food intake is allowed by cephalic reflex mediated secretion of nutrients into the gut, this stimulates bacterial growth which activates the gut brain axis via release of intestinal hormones. Short chain fatty acids produced by the microbiome fermentation are involved in satiety regulations (i.e satiety hormone PYY).
Mood & The importance of your diet
We often say you are what you eat, to a certain degree that is true. Diet as a consequence of foraging behavior is a fundamental aspect of our ecology and evolution. Diet has been reported to alter microbiome composition as little as 24h.
Changes in the human microbiome have been linked to several neuropsychiatric disorders, including autism spectrum disorder (ASD), schizophrenia, mood disorders, Parkinson’s disease (PD).
A recent study found that gut microbiome diversity is positively correlated with increased sleep efficiency, total sleep time and was negatively correlated with wake after sleep onset. There is positive correlation between microbiome diversity and interleukin-6, a cytokine that is noted for its effect on sleep. This study with 40 male participants, using actigraphy to quantify sleep measures, immune system biomarkers and neurobehavioral assessment found that hyla richness of Bacteroidetes and Firmicutes were positively correlated with sleep, Interluekin-6 concentrations and abstract thinking.
Probiotics are defined as live microorganisms that when ingested in adequate amounts have a beneficial effect on the host. Probiotics are commonly known as to have therapeutic effects on many GI disorders. Based on recent studies, there are more and more evidences of probiotics' ability to change behaviour and improve the mood, anxiety and cogitation via neurotransmitter activity.
Systematic review of the effect of probiotic on patients suffering from depression experience, significant mood, anxiety and cognitive symptoms has been carried out. During the meta-analysis of more than 100 clinical studies was examined, the resulting ten studies met the criteria and found that the majority of the studies found positive results on all measures of depressive symptoms; these assist mood, anxiety, and cognition. The study concluded that the gut microbiome and the use of probiotics could be useful in alleviating depressive symptoms
“Koso” means enzyme or ferment in Japanese. Koso drink is a century-old traditional fermented drink made from vegetables, fruits, and plants. A century-old traditional drink, Koso has good bacteria which are Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus casei, Lactococcus lactis. And galactooligosaccharide and dietary fiber are included as prebiotics. Dandelion Greens, Asparagus, apples, Burdock, Barley, Seaweeds act as prebiotics ingredients.
References:
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David LAet al.2014Diet rapidly and reproducibly alters the human gut microbiome. Nature 505, 559–563. In
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Wallace, Caroline J K, and Roumen Milev. “The Effects of Probiotics on Depressive Symptoms in Humans: a Systematic Review.” Annals of General Psychiatry, BioMed Central, 20 Feb. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5319175/.
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Naidoo, Uma. “Gut Feelings: How Food Affects Your Mood.” Harvard Health Blog, 27 Mar. 2019, www.health.harvard.edu/blog/gut-feelings-how-food-affects-your-mood-2018120715548.
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Smith, Robert P., et al. “Gut Microbiome Diversity Is Associated with Sleep Physiology in Humans.” PLOS ONE, Public Library of Science, journals.plos.org/plosone/article?id=10.1371/journal.pone.0222394#abstract0.
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Fetissov, Sergueï O. “Role of the Gut Microbiota in Host Appetite Control: Bacterial Growth to Animal Feeding Behaviour.” Nature News, Nature Publishing Group, 12 Sept. 2016, www.nature.com/articles/nrendo.2016.150.
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Cryan, John F., and Timothy G. Dinan. “Mind-Altering Microorganisms: the Impact of the Gut Microbiota on Brain and Behaviour.” Nature News, Nature Publishing Group, 12 Sept. 2012, www.nature.com/articles/nrn3346.
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Davidson, Gabrielle L., et al. “The Gut Microbiome as a Driver of Individual Variation in Cognition and Functional Behaviour.” Philosophical Transactions of the Royal Society B: Biological Sciences, 13 Aug. 2018, royalsocietypublishing.org/doi/full/10.1098/rstb.2017.0286#RSTB20170286C83.
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Rao, S. et al. Pathogen-mediated inhibition of anorexia promotes host survival and transmission. Cell 168, 503–516 (2017).