How Herbal Medicine Influences the Gut-Brain Axis: Pathways, Plants, and Practical Tips

explore the detailed science of how herbs interact with your microbiome to support mental wellness

“All disease begins in the gut.”

—Hippocrates of Kos, maybe

Whether or not Hippocrates actually said those words (historians are still debating), the idea behind them has stuck around for over two thousand years—and for good reason. The gut isn’t just a place where food gets broken down and absorbed. It’s a dynamic, responsive system that influences everything from mood to immune health. And as herbalists, this is a truth we’re starting to appreciate more than ever.

One of my favorite parts of research is asking: How did we figure this out? Who first noticed these patterns? What made someone think, "Maybe the gut does more than just digest?"

It turns out, the first clue came from a gunshot wound.

In the 1800s, in a remote corner of Michigan, a Canadian fur trader named Alexis St. Martin was accidentally shot at close range. He survived, but the injury left him with a fistula—an open hole in his stomach. His doctor, William Beaumont, saw this as a once-in-a-lifetime chance to observe digestion as it was happening.

But what stood out most to me were the little notes in the margins—Beaumont’s observations that when St. Martin was angry, upset, or anxious, his digestion slowed down.

Even in the 1800s, without any talk of neurotransmitters or the microbiome, a pattern was forming: our emotional state and our digestive function are deeply connected.

Later, scientists like Claude Bernard and Charles Darwin would build on this idea. Bernard developed the concept of the milieu intérieur—the belief that the body must maintain internal stability to stay well. We now call this homeostasis, and it’s central to everything from immune health to energy regulation. (Cryan et al., 2019)

So no, the gut-brain connection isn’t a trendy wellness buzzword. It’s an idea that’s been slowly taking shape for centuries—through observation, curiosity, and (occasionally) very strange circumstances.

And now? We’re finally starting to understand it on a deeper level.

From battlefield wounds in 19th-century Michigan to microbiome mapping in modern research labs, we’ve come a long way in understanding the gut’s influence on health. Today, we know that the gut and brain are in constant conversation—through a complex web of nerves, hormones, immune signals, and microbial messengers.

Let’s break down exactly how this communication happens.
Because when we understand the routes, we can better choose the remedies.

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What We're Covering in Today’s Article

We're diving deep into the science and herbalism behind it all. In the full (she’s a long one!) article, we’ll cover:

• The four main gut-brain communication pathways (with updated detail you didn’t get in Tuesday’s post)

• How herbs interact with the microbiome through metabolism and modulation

• Why this interaction matters for mental health, inflammation, and herbal efficacy

• Practical ways to recognize signs of gut-brain imbalance in yourself or your clients

• Thoughtful herbal strategies for supporting both gut and brain health

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