How your gut is controlling your mind

Hi there,

Have you ever had a gut feeling about something, or been told to trust your gut?

It’s not just a phrase. Your gut has more influence over your mind and body than you might realise. Your gut microbiome, the trillions of bacteria that live in your digestive tract, can impact your metabolism, immune system, and brain function.

Today we’ll cover how our gut directly affects our cravings and mood, and some new research that gives insight into how we can improve our gut health.

Why eating that second doughnut isn’t entirely your fault

First, a few quick definitions.

When we talk about the gut-brain axis, we’re not just referring to your stomach and your brain. The gut includes your entire digestive tract from end to end (mouth to… the other end). The brain in this context refers to both the central and peripheral nervous systems.

Your gut and brain are constantly interacting with each other.

There are neurons in the gut monitoring what nutrients and microbiota are present. They communicate this information to the brain. Some of them release hormones that trigger neural circuits in the brain (such as GLP-1, which tends to reduce appetite, or Ghrelin, which drives you to look for food).

What you consume impacts what happens in your brain.

If you eat a doughnut, neuropod cells in your gut are activated by the sugar and fatty acids present. They send the information on what’s present in the gut to the brain and cause the release of dopamine, which then motivates you to seek more of that type of food (a second doughnut or some other sweet food). One study showed that if you put sweet liquid directly into the gut (eliminating the taste element), you will still crave more sweets.

The drive to seek out sugary foods happens on both a conscious (we know they taste delicious - this also causes a dopamine release) and subconscious level (the gut-brain relationship described above).

How what’s happening in your gut affects your mood

The trillions of micro-organisms living in your gut aren’t just hanging out.

They’re responsible for a range of activities and can produce neurotransmitters like dopamine and serotonin (90-95% of serotonin is manufactured in the gut). Neurotransmitters travel from the gut into our bloodstream, changing our baseline levels. The baseline is what sets our overall mood. (It’s important to note that this isn’t the only source of dopamine and serotonin in our bodies - individual events can also cause neurons to release these directly.)

It’s clear from the research that our gut microbiome impacts our emotional well-being.

Mental health conditions are often accompanied by gastrointestinal disorders, and changes in the gut microbiome have been observed in people with autism spectrum disorder, anxiety, depression, and schizophrenia.

Does this mean we can feel better by optimising our microbiome?

How to improve gut health

There isn’t a clear definition of what a healthy gut microbiome looks like. But there’s evidence that increased diversity in the microbiome is associated with better health.

So, how do you increase diversity?

An exciting recent study gives us an unexpected answer: low-sugar fermented foods.

The original hypothesis of the study was that high-fibre foods would cause the most significant increase in gut microbiome diversity, but it turned out that this was not the case. The results of the high-fibre diet were mixed. On the other hand, the diet that increased low-sugar fermented foods (plain yoghurt, kefir, kimchi, sauerkraut, kombucha) showed an increase in microbiome diversity and decrease in inflammatory proteins.

So, I’m off to buy some kimchi.

If you want to learn more about the gut microbiome, take a look at these:

• Huberman Lab podcast episode 61 and episode 62 on the gut microbiome and gut health

• Neuropod Cells: The Emerging Biology of Gut-Brain Sensory Transduction (Annual Review of Neuroscience)

• Emotional well-being and gut microbiome profiles by enterotype (Nature Scientific Reports)

• Gut-microbiota-targeted diets modulate human immune status (Cell)

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Question of the week

Our body and its microscopic inhabitants influence what we think and do.

This conflicts with the concept of free will. Can we consciously make choices, or are events in our brain determined unconsciously by biological systems? Are humans just an elaborate means of allowing these microbial systems to be passed down from generation to generation?

This might seem like a depressing thought, but it’s actually quite liberating.

In a culture where we tend to be quite hard on ourselves, it can help to relieve the pressure on the mistakes we make, and the things we do or don’t do.

With that, this week’s question: If we are just sophisticated carrier bags for microbes, what changes for you?

Link of the week

My brilliant friend Lumes has a podcast! It’s about realistic self-betterment and the growing pains that come with it. I had the pleasure of joining her on an episode last week where we talked about overcoming limiting beliefs. Listen on Spotify, Apple Podcasts, or wherever you get your podcasts by searching for “The Lumes & Me Podcast”.

That’s all for now. Have a wonderful week!