One Herb Changes the Path of Another

"Could you just leave that one herb out?"

I get this question now and then. The smell is off-putting, or they heard something about that herb somewhere — the reasons vary.

It is a fair question. But there is a reason I cannot easily take one out or put one in.

I have written before about the chemistry that happens inside the pot when herbs are decocted together. (Why the herbs are decocted together in one pot) What I want to talk about today is what comes after that. It does not end in the pot. Once inside the body, they keep changing each other's paths.

Honey is not added for sweetness

Among the old prescriptions there is a method of decocting honey together with herbs whose nature is fierce. And not a token amount for taste — considerably more than the herb itself.

For a long time I read this as something added to make the medicine easier to swallow. But the material that actually measured this combination says otherwise.

When used together with honey, the blood concentration curve of that herb's compounds is redrawn entirely. The highest concentration reached, the time it takes to get there, the speed at which it leaves the body — all of it changes. And it does not move in only one direction. The class of compounds where toxicity is the concern goes down, while the class we want as medicine comes through more.

Honey did not step on the brake. It is closer to redeciding what gets through, and how much. The same herb, and yet what arrives in the body differs depending on what sits next to it.

Some herbs hold both the door and the enzyme at once

The body has doors that push what we have eaten back out, and the liver has enzymes that break it down. How much of a medicine stays in the body is decided in large part at these two places.

The compounds in bitter yellow herbs like coptis hold both of these at once. The pushing-out weakens and the breaking-down slows, so the concentration of whatever else came in alongside rises.

This has been measured in people. Seventeen healthy adults took this compound for two weeks, and the handling of other drugs was measured: the activity of three enzyme types all fell. For one drug, total exposure in the body rose by 40%.

But this study was done with the compound isolated and given at a set dose, continuously. I cannot say it would reproduce the same way when the herb goes in alongside others inside a prescription. Still, the direction is clear. This herb affects its neighbors.

So where such an herb belongs, I use combinations that have long been in use rather than adding and subtracting on my own. I am not claiming the old physicians knew this mechanism. Only that a combination which survived a long time already has the adjustment built into it, and if I move one piece of it, even I do not fully know what else moves with it.

There are several layers, and they switch on at different times

Put this way it may sound like herbs simply helping or hindering each other, but it is not one layer.

The same herb has a hand in its neighbor once in the decoction pot, again when it is absorbed in the gut, and once more when the liver processes it. And these layers do not switch on at the same moment. The work in the pot is already finished; absorption happens within tens of minutes; the effect on breakdown can show up over days.

The picture I keep coming back to holds here too. Many hands push different parts of a large ball, with different strength, at different moments, and the ball rolls in one direction. (Herbal medicine does not press on one place) Take one hand away and the ball does not simply slow down — the direction it rolls changes.

So what I look at when placing a single herb

Three things, put simply.

What the herb does on its own. What it holds, and what it opens.

Its relationship with what sits beside it. How, going in together, they change each other's extraction, absorption, and breakdown.

That person's condition. Whether they are taking anything now, and what state the body is in.

The third matters most. The same combination reads differently when there is a medication already in the picture. As I said above, an herb can slow the breakdown of a drug, and then that drug's concentration rises. If you are taking anything, please do tell me. Most of the time the answer is that you can take them as they are, but that is not a judgment I can make without the information.

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We started with the question of whether one herb could simply be left out.

The answer is this. It can be. But that is not removing one thing — it is changing the path of everything else along with it. Which is why I do not move that piece lightly.

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References

• How the blood concentration curve and the balance of toxic compounds shift when used together with honey — Frontiers in Pharmacology, 2025
• Enzyme activity that breaks down drugs fell after two weeks of dosing in humans — European Journal of Clinical Pharmacology, 2012

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