Gut feelings: harnessing the gut-brain connection to improve mood

Harnessing the gut-brain connection to improve mood

How we feel emotionally really resonates in our gut. When we get nervous about something or feel that something isn’t right, for example, we literally feel “butterflies” in our stomach, right? And stressful experiences can drastically change our appetite from urgent food cravings – “I just need chocolate now!” - to zero appetite.

But how are our emotions actually transferred to our gut? And how does our gut then influence our moods?

The key link for transferring your emotional intuitions from your brain down to your gut is the vagus nerve – this is a physical representation of the mind-body connection.

The vagus is the longest cranial nerve in the body – starting at the base of the brain and running down your neck into the body. Random but fun fact: Vagus literally means “wanderer” in Latin, aptly named as the nerve’s many branches roam around the body linking your brain to vital organs within the body, including the gut, heart, kidneys and lungs (1).

...researchers have shown that regulation of the vagus nerve is super essential for responding effectively to stressful everyday experiences.

Communication between the body and brain via the vagus goes in both directions, allowing constant monitoring, reports and reactions. In fact (and most importantly for you here), researchers have shown that regulation of the vagus nerve is super essential for responding effectively to stressful everyday experiences. Basically, keeping your vagus in check helps you fight back against the negative effects of stress, something we’re all about at NeuroTrition!

But, to really understand the role of the vagus in stress responding we first need to dig a little into the systems that keep our body in balance.

Your Nervous System 101

Your autonomic nervous system (ANS) is an unconscious, automatic system that manages our essential bodily functions – things like our heartbeat, breathing, digestion and excreting waste, that we hopefully don’t have to spend any time thinking about. The ANS is divided into two complementary teams that work hand-in-hand, the sympathetic and parasympathetic nervous systems.

When we are stressed out the sympathetic nervous system - also known as the “fight or flight” response - kicks in to provide mental alertness and the energy to escape or defend ourselves. But when we are relaxed the parasympathetic nervous system – also known as the “rest and digest” system – is active. The vagus nerve, interestingly is a key part of the parasympathetic nervous system.

Clearly the balance between our sympathetic and parasympathetic nervous systems has a huge impact on physical and mental health. Chronically stressful lifestyles can lead to our parasympathetic (“rest and digest”) nervous system being drowned out by a hyperactive sympathetic (“fight or flight”) system, resulting in high blood pressure and cardiovascular diseases, type two diabetes and obesity. For a primer on how stress affects your body, see this blog by our Science Council member and resident stress expert Dr Matt Hill.

Feeling the beat

Did you know that scientists can actually stimulate the vagus directly using tiny electrodes to “turn up” it’s effects? Stimulating the branch of the vagus that connects to the heart, for example, slows down the heartbeat – reducing blood pressure (2). Increasing vagus activity is even an emerging therapy for heart failure as it directly controls cardiac function, rather than relying on drugs (3). This has me really excited because it speaks so perfectly to our motto of going Beyond The Band-Aid.

Knowing that we can stimulate the vagus provides avenues to control other bodily functions, so it has become a potential target for treating both mental health and gut disorders. Exciting!

Gut feelings

The parasympathetic nervous system, including the vagus nerve, tells the gut that it’s ok to get to work digesting food. But the vagus has another foodie role by providing a route for the hunger hormone ghrelin to talk to the brain to control eating behaviour (4).

Our gut actually contains its own independent “mini-brain” – a complex network of neurons called the enteric nervous system.

Our gut actually contains its own independent “mini-brain” – a complex network of neurons called the enteric nervous system. You might have heard us talk about the “gut-brain axis” before (I even went on a Canadian speaking tour this past Fall to spark and spread the gut-brain axis love), and this is what we’re talking about. The gut-brain axis is the complex communication link between the brain and the enteric nervous system (and some “bugs”, but more on that later).

Stimulating the vagus in the gut can boost levels of brain chemicals - called “neurotransmitters” – involved in mood including serotonin and noradrenalin (5). SSRI’s (selective serotonin reuptake inhibitors) are a class of antidepressant that increase serotonin in an attempt to manage depression, so scientists think that activation of vagus could act like a drug-free antidepressant (6). Super amazing, in my opinion - can you imagine vagus nerve activation to fight depression!?!

But there are many more players in the gut-brain axis, enter the microbes that call our intestines home…

Friends with benefits the gut microbiome

The community of trillions of bacteria and microbes that inhabit the intestines is known as the “gut microbiota” – those gut bugs we’re obsessed with these days at NeuroTrition, and that you’re probably hearing a lot about. You may have heard that these gut bugs chat with neurons in your local enteric nervous system, but did you know they can also influence the brain by long distance calls via the vagus (7)?!

Science tells us that some types of gut bugs, including the probiotic Lactobaccilus rhamnosus have anti-anxiety properties. How, you might ask? Well, they can message brain cells via the vagus encouraging them to release GABA, a neurotransmitter that promotes calmness (8). Are probiotics the new Valium (but without the side effects and nutrient depletions)? I don’t know about that (yet) but am keeping my finger on the pulse of this research and feel hopeful that these gut bugs are going to be capable of helping people struggling with anxiety.

Researchers have now shown that the vagus nerve is the vital communication route for these microbes to get their messages across (8). Gut bugs can also increase neuroplasticity (ie. growth, changes, connectivity) in the brain - which is closely linked to mood (9), but again the vagus is needed to get the microbial messages across, particularly to the brain’s memory centre - the hippocampus (10).

The vagus can calm inflammatory events

Our emotions can manifest in our digestive health, which you’ve probably also noticed, and this often goes hand in hand with inflammation. I see this co-morbidity of mental health and digestive imbalances A LOT with our clients, and a recent Canadian study validated my anecdotal observations at the office by showing that a quarter of inflammatory bowel disease patients also suffered from depression and anxiety (11). 

Chronic inflammation propagates pain, autoimmune disease and mental health disorders, and vagus nerve signals are key to quenching inflammatory responses.

Chronic inflammation propagates pain, autoimmune disease and mental health disorders, and vagus nerve signals are key to quenching inflammatory responses (12). While we are far off from saying that a healthy and happy, stimulated vagus nerve is akin to anti-inflammatory drugs like Advil, NSAIDs (non-steroidal anti-inflammatory drugs) or prednisone, a recent clinical study has shown that stimulating the vagus nerve reduced inflammation in people with rheumatoid arthritis, improving their symptoms (12). So the research in this area has started (thank God, because these meds are so brutal long-term!), and I can’t wait to see where it goes. Now, are you ready to show your vagus nerve a little love?

How to talk to your vagus 2 ways!

Ok, so the vagus nerve is a key player in the gut-brain axis and mental health to promote relaxation and calmness. But can we stimulate it ourselves, to feel relaxed and calm?? That’s what I was itching to find out as I delved into the scientific literature.

The vagus nerve branches out to your throat, lungs, heart and intestines. And science tells us that the vagus can in fact be stimulated in your throat and through breathing. Perfect. But let’s dig a little deeper, shall we?

Gargling, singing and humming (all brought up in various Google searches as bona fide ways to stimulate the vagus nerve) all do vibrate our vocal chords, which can lift our mood - who doesn’t feel happy after belting out a song in the shower? But the two legit, scientifically demonstrated methods of vagus stimulation to date are through 1.) specific breathing techniques and 2.) altering our gut flora.

1. Breathing techniques

A. Diaphragmatic breathing is when the breath is slowed to 5-7 breaths per minute. The diaphragm is stimulated by the long and slow exhalation of breath, reducing heart beats and relieving stress (13).

B. Yogic breathing is used in yoga to calm the mind (13). During “Ujjayi Pranayama” you completely fill your lungs, while slightly contracting your throat, and exhale slowly - stimulating the vagus in both the diaphragm and the throat. So practicing yoga, or just using yogic breathing methods can help calm a racing mind.

2. Prebiotics and probiotics

Our gut bugs quickly respond to changes in our diets and environment. Cutting-edge research is now harnessing “psychobiotics” – mood altering microbes – to improve brain and mental health conditions (14), which we are so all over! And it turns out that keeping our microbiome nourished with lots of gut-friendly fermented foods, fresh fruit, veggies and fibre is a great way to keep your vagus well-fed, too.

Science shows that the vagus is key for restoring balance in our hectic lives. So next time you are super stressed out, try some vagus stimulating breathing techniques and reach for foods brimming with probiotics and prebiotics (check out this blog on prebiotics). Your brain and gut will thank you for it!

References
  1. Berthoud, H. R., & Neuhuber, W. L. (2000). Functional and chemical anatomy of the afferent vagal system. Autonomic Neuroscience: Basic and Clinical, 85(1), 1-17.
  2. Buschman, H. P., Storm, C. J., Duncker, D. J., Verdouw, P. D., van der Aa, H. E., & van der Kemp, P. (2006). Heart rate control via vagus nerve stimulation. Neuromodulation: Technology at the Neural Interface, 9(3), 214-220.
  3. Ardell, J. L., Nier, H., Hammer, M., Southerland, E. M., Ardell, C. L., Beaumont, E., ... & Armour, J. A. (2017). Defining the neural fulcrum for chronic vagus nerve stimulation: implications for integrated cardiac control. The Journal of physiology, 595(22), 6887-6903.
  4. Browning, K. N., Verheijden, S., & Boeckxstaens, G. E. (2017). The vagus nerve in appetite regulation, mood, and intestinal inflammation. Gastroenterology, 152(4), 730-744.
  5. Manta, S., Dong, J., Debonnel, G., & Blier, P. (2009). Enhancement of the function of rat serotonin and norepinephrine neurons by sustained vagus nerve stimulation. Journal of psychiatry & neuroscience: JPN, 34(4), 272.
  6. Grimonprez, A., Raedt, R., Portelli, J., Dauwe, I., Larsen, L. E., Bouckaert, C., ... & Boon, P. (2015). The antidepressant-like effect of vagus nerve stimulation is mediated through the locus coeruleus. Journal of psychiatric research, 68, 1-7.
  7. Kim, N., Yun, M., Oh, Y. J., & Choi, H. J. (2018). Mind-altering with the gut: Modulation of the gut-brain axis with probiotics. Journal of Microbiology, 56(3), 172-182.
  8. Bravo, J. A., Forsythe, P., Chew, M. V., Escaravage, E., Savignac, H. M., Dinan, T. G., ... & Cryan, J. F. (2011). Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proceedings of the National Academy of Sciences, 108(38), 16050-16055.
  9. Fung, T. C., Olson, C. A., & Hsiao, E. Y. (2017). Interactions between the microbiota, immune and nervous systems in health and disease. Nature neuroscience, 20(2), 145.
  10. O’Leary, O. F., Ogbonnaya, E. S., Felice, D., Levone, B. R., Conroy, L. C., Fitzgerald, P., ... & Cryan, J. F. (2018). The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus. European Neuropsychopharmacology, 28(2), 307-316.
  11. Byrne, G., Rosenfeld, G., Leung, Y., Qian, H., Raudzus, J., Nunez, C., & Bressler, B. (2017). Prevalence of Anxiety and Depression in Patients with Inflammatory Bowel Disease. Canadian Journal of Gastroenterology and Hepatology, 2017.
  12. Koopman, F. A., Chavan, S. S., Miljko, S., Grazio, S., Sokolovic, S., Schuurman, P. R., ... & Tracey, K. J. (2016). Vagus nerve stimulation inhibits cytokine production and attenuates disease severity in rheumatoid arthritis. Proceedings of the National Academy of Sciences, 113(29), 8284-8289.
  13. Streeter, C. C., Gerbarg, P. L., Saper, R. B., Ciraulo, D. A., & Brown, R. P. (2012). Effects of yoga on the autonomic nervous system, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder. Medical hypotheses, 78(5), 571-579.
  14. Bruce-Keller, A., Salbaum, J. M., & Berthoud, H. R. (2017). Harnessing Gut Microbes for Mental Health: Getting From Here to There. Biological psychiatry.

 

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