Your Gut = Second Brain. Here's Why

Good morning!

If you have been lurking around the corners of the health side of social media you may have heard phrases like, “The gut is the second brain of the body” or “The gut is responsible for everything from depression to low immune systems”.

If you’re anything like me that seems pretty hard to believe. I mean, it doesn’t really explain how the cumulative effect of trillions of bacteria in our gut (organisms that aren’t strictly part of our body) can influence our psyche.

So, let’s hop into the latest trend in science… bacteria in the gut as our second brain!

Key Takeaways:

• The gut is the body’s “second brain,” powered by over 100 million neurons in the enteric nervous system.

• When your gut gets irritated or unbalanced, it can send signals that trigger anxiety and depression.

• Gut bacteria create neurotransmitter precursors that reach your brain and help shape your mood.

CORE

Why is it Called the Second Brain?

The truth is that what is called the second brain isn’t the bacteria themselves, that is simply a common misconception that roams freely across the internet.

The second brain refers to the enteric nervous system (ENS) that packs neurons into the walls of your entire digestive system. Basically following the food from start to finish. The ENS contains over 100 million neurons, more than your spinal cord! But its functions are far reaching and we have just started to scratch the surface.

The ENS is responsible for helping maintain the peristaltic contractions that are kind of like waves that move everything towards the finish line stopping it from moving back from where it came. But it also makes us “feel” things in our gut.

When the ceviche that we ate last night didn’t sit quite well boy do we feel it. When it’s empty it signals the brain to start producing the hunger hormones (ghrelin). But the brain does more than that!

In the wise words of Emeran Mayer, professor of physiology, psychiatry and bio-behavioral sciences, “The system is way too complicated to have evolved only to make sure things move out your colon.” What a poet!

The Gut’s Emotions

Even though it would seem ludicrous to say that our gut is capable of complex thought, rational thinking, and interpreting reality, it seems that it does have considerable influence over our emotional state.

For years science was convinced that a depressive or anxious state signaled to the enteric nervous system that we aren’t doing well and that was what triggered syndromes like IBS or irritable bowel syndrome. But the new frontier of gut sciences says that it may very well be the other way around.

According to John Hopkins Medicine, new findings indicate that the relationship may very well be the other way around, and that irritation in the gut may cause altered emotional states triggered by the ENS. This could explain why people that experience IBS experience higher than normal percentages of anxiety and depression.

Bacterial Underworld

Ok, now we know why people consider the gut to be the second brain and it seems that they have a solid point. That said, there’s still a lot we don’t fully understand about all the ways it affects our physical and mental health. What we do know is this, gut bacteria do way more than just munch on leftovers.

Their effect can be grouped into two main categories: 

First: our microbiome is dynamic and constantly changing. You need a balance of good bacteria (even too much of one strain is bad) and you also need to limit the bad bacteria.

Changes in this critical balance can cause the gut to become inflamed and cause two things:

• Low-grade inflammation across the body. To read more on inflammation press here!

• When the gut becomes irritated, that can signal your central nervous system to trigger unwanted emotional changes, as the Johns Hopkins research shows.

Second: bacteria, like humans, produce neurotransmitters. These can either enhance our body’s own neurotransmitter production or work against it.

Here are some of the most common neurotransmitters produced by bacteria: 

• Glutamate

• GABA

• Dopamine

• Norepinephrine

• Serotonin

• Histamine

• Acetylcholine

Any of these ring a bell? If you’re a regular reader, I know they do!

It might seem like gut bacteria could directly control your mood, but the neurotransmitters they produce can’t cross the blood-brain barrier (BBB). That means they affect your body, but not your brain. So they don’t directly change how you feel. Sorry, no gut-brain Wi-Fi yet!

What they can do is make precursors (building blocks for those neurotransmitters) that can pass through the BBB. Once inside the brain, they’re converted into the actual neurotransmitters that influence mood.

So whatever way you slice it, gut bacteria play a role in regulating your emotions one way or another.

PRODUCT MENTION

Tense muscles don’t just make your body tight, they send stress signals through your nervous system. Your gut, as a second brain, receives these signals and can respond with changes in digestion, gut activity, and emotional cues.

OmniBlue’s Magnesium Spray relaxes muscles by blocking calcium, reducing these stress signals. At the same time, it boosts GABA naturally, helping your nervous system (and your gut-brain network) feel calmer and more balanced.

Support your second brain today. Grab your own magnesium spray and give your gut the calm it deserves.

CORE

Learn More

So here’s the connection: the food you eat doesn’t just fuel your body, it feeds your gut bacteria. And those bacteria? They’re running your second brain, influencing digestion, mood, and more. Curious how to support them?

Check out our pre/pro/postbiotic newsletter to see how to keep your little brain-helpers thriving.

ENDNOTE

Final Thoughts

Think about it: you have a second brain in your gut. Not a metaphor, not a figure of speech. A real, neuron-packed command center quietly influencing your mood, your cravings, your digestion… all while you go about your day. It’s insane. And the more you learn about it, the harder it is to ignore that your body is basically running a second mind down there.

Until next week!

Adrian Macdonald | Team Dietitian | The 8% Newsletter Author