The most important information I’ve learnt to date is that we have two brains. I mean, not literally. But, there are two things (bodily functions) that effect how we think, feel, and how our body works.

illustration black man with red brain representing mental health — We’ve got our brain (check) and our guts.

The reason scientists call our gut our “second brain” is because it has almost the same influence over us as our actual brain. Our first brain is pretty far away from the rest of our body and doesn’t actually come into contact with the blood pumping around our body. So, it doesn’t really know what’s going on. Luckily, it’s linked to the rest of our body through nerves, which gives it an idea.

The vagus nerve is the big boy that’s responsible for our parasympathetic nervous system which is in charge of digestion, heart rate, breathing and a whole load of other important stuff (1) (2). Arguably, it’s most important job is that it links our gut (second brain) to our first brain. This is called the gut-brain axis.

The reason this is so important is because 70%-80% of our immune system is in our gut (6). On top of this, our gut makes over 90% of our serotonin (nickname: the happy hormone) (7). So, our guts are basically like the ground crew who send messages to the pilot (our brain) when something’s up, through our vagus nerve, and vice versa.

how is the gut so intelligent?

The reason behind all of this is down to these lovely little creatures living inside our large intestine called microbes.

illustration of blue man with green background representing bacteria and microbiome in the body — Photo by Monstera: https://www.pexels.com/photo/paper-applique-of-human-figure-with-bacteria-5841764/

We have billions of microbes living inside our gut. We literally have more microbes than human cells (we’re essentially only 10% human (3)). Together, they make up our microbiome. These little guys play a vital role in our survival.

small green army men preparing to fight war — Think of them like a little army living inside our bodies that protect us against any invaders looking to attack. As well as protecting us against diseases, viruses and bacteria, they also help to break down the food we eat.

By doing this, they basically dictate how much calories and nutrients we get from food (5). This is why calories (a measurement of energy) vary from person to person, it’s all in our guts.

So, if there’s anything going on in the body (i.e., malnutrition, low energy, low blood sugar, invaders) our microbiome sends the brain a message through the vagus nerve. As our brains don’t speak “microbe”, the vagus nerve translates the message so the brain can then decide what to do (4). The same goes for when the brain needs to send a message to our guts. These messages are usually sent by serotonin.

line drawing illustration of microbiome, vagus nerve and brain interactions — Too much or too little serotonin in the brain relates to anxiety and depression (7), which is how our guts effects our mental health.

Much like ground control, the majority of the messages sent between both brains are bad news. So, cortisol (the primary stress hormone) is released and our body preps for “fight, flight or freeze”. This is our primal response to danger. It takes our body out of “rest and digest”, meaning that our digestive system grounds to a halt, our heart rate rises, pupils dilate, etc. (think of Alex in Madagascar when he sees Marty as a steak). It’s an automatic response used to protect us. But, it can also be pretty damaging.

Our brain can now manifest its own dangers (anxiety, rumination, fretting about the future) which activates this. When this happens, our amygdala takes over from our prefrontal cortex (where our rational decisions are made). We’re not digesting our food properly, so we’re not getting the right nutrients or calories. So, we crave sugar, fat and carbs. Which, again, doesn’t give us the nutrients we need. This also kills off a lot of our good bacteria that protect us from disease, inflammation and serotonin release (relating to depression and anxiety). Signals are then sent back up the vagus nerve to alert the brain that something’s not right.

Cortisol also makes us store more fat (to prep us for danger). And, in the western world fat is not “sexy”. So, more stress. More signals through the vagus nerve. Further activation of our fight or flight.

two eggs with a sad, concerned and anrgy face

so, how do we get out of this?

It seems as though we’re stuck in this loop, perpetuated by the food we eat and the society we live in. But, we can get out of it, and it’s a lot simpler than it seems.

line drawing illustration of a running man wearing trainers and a sweat band with his tongue out — **movement, meals and meditation.**

If our body is prepped for fight or flight, then we need to move. Running, yoga, swimming, walking - whatever works for you. They’ve all been proved to reduce stress, anxiety and depression - more so than SSRIs (antidepressants) (8). It works by improving the tone of the vagus nerve (better signal between flight and ground crew), influences serotonin (making us happier and calmer) and increases the diversity of the microbiome (strengthening our inner army).

Another thing that increases it? Food.

When you’re in your fight or flight and you’re craving that double bacon cheeseburger, but are told to eat a salad, it probably pisses you off a bit. Or, a lot. So, instead of taking away, add on. Maybe just go for a cheeseburger (drop the double) and add in some more vegetables.

photo of a gourmet burger with spinach and caramelised onions — That way your still feeding you’re microbiome and you’re getting more nutrients, which means (eventually) you’ll stop craving the fat, carbs and sugar as your body gets back into equilibrium.

But, we still need to calm ourselves down, and get into “rest and digest” so that we can absorb these nutrients. This is where meditation comes in.

Meditation calms down the nervous system, gets us out of our anxious minds and back into our body. Basically, it snaps us out of “fight, flight or freeze” and back into “rest and digest”. When we’re feeling stressed, some breath work followed by a short meditation before eating will do you so much good.

dark photo of a woman meditating with soft lighting

It really is so simple, a prevention for disease and (the best part) - it’s free.

By following the 3 Ms: movement, meals and meditation, we get ourselves out of the “fight, flight or freeze” loop and feed our microbiome which protect us from the inside. That way, if any external stressors arise, we’re able to deal with them a lot quicker and a lot more rationally.

references:

1. Breit, S.; Kupferberg, A.; Rogler, G. and Hasler, G. (2018). ‘Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders’, Frontiers in Psychiatry, 9.49, 44: 1-15. (accessed 25 August 2022)

2. Collen, A. (2015) 10% Human: How Your Body’s Microbes Hold the Key to Health and Happiness, London: William Collins (accessed 25 August 2022)

3. Bonaz, B.; Bazin, T. and Pellissier, S. (2018) ‘ The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis ’, Frontiers in Neuroscience 12.49: 1-9 (accessed 25 August 2022).

4. Spector, T. (2015) The Diet Myth: The Real Science Behind What We Eat, London: Weidenfeld & Nicolson (accessed 25 August 2022)

5. Wiertsema, S.P; van Bergenhenegouwen, J; Garssen, J. and Knippels, L.M.J. (2021). ‘The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies’, Nutrients 13.3: 886 (accessed 25 August 2022)

6. Martin, C.R.; Osadchiy, V.; Kalani, A. and Mayer, E.A. (2018). ‘The Brain-Gut-Microbiome Axis’, Cellular and Molecular Gastroenterology and Hepatology 6.2: 133-148 (accessed 25 August 2022)

7. Dalton, A.; Mermier, C. and Zuhl, M. (2019). ‘Exercise Influence on the Microbiome–Gut–Brain Axis’, Gut Microbes 10.5: 555-568 (accessed 25 August 2022)

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