The vagus nerve
The vagus nerve is smack bang in the middle of the gut–brain axis and is incredibly important.A recent study involved administering Lactobacillus reuteri to mice with autism-like behaviours via the vagus nerve. L. reuteri is a probiotic bacteria that is found the gastrointestinal tract, urinary tract, skin, and breast milk of humans and other mammals.
The authors had discovered in 2016 that the offspring of mice fed a high-fat diet had a reduction in the bacterial species L. reuteri, and this led to social deficits (perhaps applicable to us socially awkward humans too). Importantly, in this study, when restored, the L. reuteri reversed the social deficits.
The researchers then severed the vagus nerve in the mice, and as a result L. reuteri had no effect on social behaviour in autistic mice. This indicates that the vagus nerve sends microbiome messages from the depths of the gut to the heights of our brain. It’s like an old school telephone sending messages along a phone line.
The vagus nerve also plays a role in reducing inflammation. It operates a network of fibres that surround our organs, and relays information regarding the presence of inflammatory mediators. It acts like a spy that passes information about inflammation to the brain, so then the brain can respond and regulate the body’s immune response.
Looking after your vagus nerve
Balancing the microbiome can increase the tone of the vagus nerve, which then increases parasympathetic nervous system activation and calms us.
We can also increase the tone of the vagus nerve through meditation, humming or gargling, or slow, rhythmic, diaphragmatic breathing. Singing is a great way to stimulate the vagus nerve and increase tone.
Acute cold exposure has been shown to activate the vagus nerve and activate cholinergic neurons through vagus nerve pathways. Studies have also found that exposure to cold can reduce your sympathetic “fight or flight” response and increase parasympathetic activity through the vagus nerve. I often take cold showers for at least 2 minutes.
Deep and slow breathing is another way to stimulate your vagus nerve. Most people take about 10 to 14 breaths each minute so in slowing down breathing and taking about 6 breaths over the course of a minute is a great way to relieve stress. You should breathe in deeply from your diaphragm and exhale long and slow. This is key to stimulating the vagus nerve and calming your nervous system.
Increasing tone is associated with reduced inflammation, increased emotional regulation and reduced anxiety – and who doesn’t want that, right?
Looking after the vagus nerve is important for gut–brain axis and will assist in the reduction of inflammation for a healthy mind.
[i]S Breit, A Kupferberg, G Rogler et al.(2018). Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in psychiatry. Vol 9 p 44. doi:10.3389/fpsyt.2018.00044
[ii]M Sgritta, S Dooling, S Buffington et al. (2018). Mechanisms Underlying Microbial-Mediated Changes in Social Behavior in Mouse Models of Autism Spectrum Disorder. Neuron. 101. 10.1016/j.neuron.11.018
[iii]Q Mu, VJ Tavella, XM Luo (2018). Role of Lactobacillus reuteri in Human Health and Diseases. Frontiers in microbiology. Vol 9 p.757. doi:10.3389/fmicb.2018.00757