Why Herbal Medicine Works — The Paradox of Low Concentration

Herbal medicine is gentle, but weak. That is how many people understand it.

I have spent years studying herbal medicines at the level of their compounds and their actions. Along the way, I ran into a paradox.

Measure it and it really is low

This is not an impression. The numbers say so.

A compound that needs micromolar concentrations to do anything in a test tube turns up in human blood at nanomolar levels. That is roughly a thousandfold lower.

Anyone who studies this field stops here at least once. If it is this low, why does the body respond at all?

But there is a premise hiding in the question

Let's stop here a moment. Why does "nanomolar in the blood" sound like a paradox?

Because we assumed the medicine rides the blood to its target. On that premise, the blood level is the medicine's strength. So if it's low, it shouldn't work. Fair enough.

But there are routes that don't use that premise.

Compounds that dissolve readily in oil — the volatile oils among them — pass straight through the oily membrane around a cell. No door, and nothing needed to carry them. Some compounds knock on the doors of the gut's mucosal cells before they are even absorbed. The gut's nerves may also read that signal and send it straight to the central nervous system without passing through the blood.

On these routes the blood level is not the medicine's strength. We are measuring in the wrong place — taking readings in the corridor for something happening in the lecture hall.

So half the paradox dissolves like this — we were only measuring the route that goes through the blood. The other half is below.

It does not act in the form you swallow — and this is one route among several

On the route that does go through the blood, the clue is that herbal medicine doesn't work in the form you swallow.

A good many of the active compounds are glycosides — a sugar is attached, and in that state the body cannot make much use of them. They pass through the stomach and small intestine, and only when they meet the microbes of the large intestine does the sugar come away, leaving a form the body can finally use.

Ginseng is like this. In the form you swallow, it is barely detectable in the blood. What is actually absorbed is the substance that appears after gut bacteria have worked on it. This pathway is an area that research here in Korea has led in mapping.

What interests me is that it differs from person to person. One study looked at the gut bacteria of a hundred people. Some people's guts cleaved the sugar off readily; others barely did so at all. What separated them was whether they carried particular bacteria, and it had nothing to do with age or sex.

Which means that the same medicine yields different amounts of active compound in different people. This is why, whether someone comes to me for pain or for an autonomic problem, I always look at digestion and the gut alongside it.

That said, this is one route among several. Explain herbal medicine by this route alone and the entrance becomes a single door. And this route is slow — the compound has to travel all the way to the large intestine and meet the bacteria there. It works on a different timing from the route described earlier, the one that passes straight through the membrane. (Herbal medicine does not press on one place)

Why a low concentration is not a weakness

The concentration is still low, though — even after metabolism has sent the compound into the blood.

Here is where hormesis enters: the phenomenon in which a low stimulus actually raises the body's capacity to regulate itself.

The researchers who set out this concept pointed at exactly our problem. For plant compounds to act as antioxidants directly, you would need concentrations no person could consume. Yet effects appear far below that. The compound is not doing the work itself — it switches on the repair machinery already inside the body. Given a mild stress signal, the cell brings its defenses and its repair systems online.

Exercise is good for you along the same grain. A moderate stress placed on muscle calls up a recovery response.

There is no need to strike hard. You only need to speak so you can be understood.

Herbal medicine is comparatively safe not because its compounds are weak, but because it is a signal of a size the body can regulate on its own.

The body does not read strength alone

It is not only concentration. The body also reads the rhythm of what arrives.

Parathyroid hormone is one example. This hormone dissolves bone. And yet give it in interrupted pulses and bone increases instead. Give it continuously and it still dissolves bone, even at a lower dose.

What does the work is not the amount but the interruption itself. The same substance, with only its manner of arrival changed, and the result turns over into its opposite.

That Korean medicine has long weighed the timing and spacing of a dose is something I read alongside this passage. The old physicians could not have known this chemistry. They noticed through the body that when and how you give something changes the outcome, and a name is now being attached to that place. This is the kind of thing that makes studying this medicine a pleasure.

Before choosing a herb, I look at the gut

A low concentration does not mean the medicine is weak. It means it works by a different route. It wakes up by way of the gut, touches the body's regulation with a low stimulus, and rides in on a rhythm.

So before I choose a medicine, I look at that person's gut, and we decide together how much to take and when. (Why medicine wakes up where it hurts)

Herbal medicine does not solve everything, of course. When it is called for, I recommend testing or other clinical care first. (What herbal medicine does)

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For a long time it puzzled me that something works at so low a concentration.

Now I see it the other way around. It is closer to working because it is low. Instead of pushing hard, it speaks at a size the body can take in, and the body does the rest.

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References

• Gut bacteria differ from person to person — and so did how much active compound was produced from the same herb — PLoS One, 2013
• Plant compounds work not by striking hard, but by switching on the body's repair pathways at low concentrations — Dose-Response, 2007
• Parathyroid hormone builds bone when given in pulses, and dissolves bone when given continuously — Bone & Joint Research, 2017

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