The Road Medicine Takes to the Brain Without Going Through the Blood — There Is a Telephone Line in the Gut

When you take medicine, most of us know it goes like this. You swallow it → the gut absorbs it → it rides the blood through the body → it arrives at the target.

It is not a wrong picture. It is just one road among several. Today I want to describe one road that does not appear in that picture.

The gut is not an organ that only digests

The gut has a great many nerves. Nerves regulating digestion are laid densely along the gut wall, and a good number of them connect to the line running up to the brain.

What matters here is the direction. We usually think of the brain giving orders to the gut — the way your stomach hurts when you are tense. But the line runs both ways. And in fact there are far more signals going up from the gut to the brain.

The gut is also an organ that reports to the brain.

That line does not go through the blood

This is the heart of it.

When something reaches the gut and touches those nerves, the signal travels straight up along the nerve. It does not need to be absorbed. It does not need to be loaded into the blood. It is like going along a telephone line.

So this road is fast. It skips the whole stage of absorbing and carrying.

And a signal going by this road will not be caught however hard you search the blood. It is a road you cannot see by measuring compounds. If you look only at blood concentration and say "this medicine is present in too small an amount to do much," this road drops out entirely. (Why herbal medicine works — the paradox of low concentration)

Sometimes it knocks on a door right where it is

There is one more road.

The cells making up the gut's mucosa have doors (channels). Some compounds, before being absorbed, knock directly on these doors right where they are. The cell responds, and that response in turn touches the nerve beside it.

Work has begun although it has not even entered the body yet.

So it is felt the moment you take it

"The moment I swallow the medicine, I feel my stomach ease."

Some people say this to me. I do not put it down to imagination. (Some medicines are felt the moment you take them)

For a glycoside compound to go down to the large bowel and meet bacteria takes hours. It cannot be felt within that time. But the road along the gut's nerves and the road knocking on the mucosa's doors do not need that time.

The same medicine, and different arrival times. There is a share that comes first and a share that comes later.

Why this road matters

I have my own reason for caring about this road.

I often see people whose autonomic nervous system has been shaken. Their tests come back normal, and yet sleep will not come, the chest races, digestion will not go, the tension will not let go. (Why the autonomic nervous system shakes the whole body)

I thought for a long time about why working on the gut helps these people. The gut getting better and digestion easing was not enough of an explanation on its own.

If there is a line running up from the gut to the brain, the story is different. The state of the gut gets reported upward along that line. If the gut stays noisy, upstairs keeps receiving that signal. Conversely, when the gut quietens, the signal going up changes too.

So I ask about the gut even with someone who has come for tension or insomnia. I ask even when there are no digestive symptoms.

How far this has been established

To put it in order.

That there is a line from the gut to the brain, and that this line does not go through the blood — this is what physiology deals with. In medicine this line is called the vagus nerve.

Which herbal compound touches which point of that line, and how much, is still being worked out one piece at a time. I take it that this road is genuinely at work in practice, but I cannot tell you which herb touches which nerve and by how much.

I am trying not to skip over that gap. That a road exists, and what goes along it and how much, are two different stories.

So in the clinic

I ask, "when did you start to feel it?" If it was right after taking it, this road opened; if it was some days later, it was a different road.

I ask about the gut even when there are no digestive symptoms. I ask even when someone has come for sleep, tension, or palpitations.

I do not read a low blood concentration as meaning the medicine is weak. It may only be that the way of measuring cannot catch that road.

---

Medicine is absorbed and spreads through the blood — this picture is correct. It is just not all of it.

The gut has a line running straight up to the brain, and that line does not go through the blood. Here too lies a reason why what herbal medicine does in the body cannot be drawn as a single line. (What herbal medicine does)

---

References

• The vagus nerve — the nerve carrying sensory information up to the brain from the organs of the abdomen and chest — Asan Medical Center, Medical Information
• A review setting out that in this nerve the side going up to the brain outnumbers the side coming down — Neuron, 2022
• The time it took for a stimulus in the gut to reach the brainstem across a single synapse — less than a second — Science, 2018 (mice)

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)