Is It True You Must Avoid Radish and Mung Beans While Taking Herbal Medicine?

"You can't eat radish while taking herbal medicine, right? Mung beans too?"

Nearly everyone who comes to the clinic asks me this. When I ask where they heard it, most say, "Well, everyone says so."

Today I want to go through these old taboos one by one. For some, today's chemistry can follow the reason all the way down. For others, the explanation has not reached that far yet.

First, the ones whose reason can be named

It is only right to start here. These are the ones worth being careful about.

Alcohol.
The liver is the organ that processes medicine, and alcohol is processed in the same place. But what alcohol does is a little more wry than "it adds a burden." Drink it all at once and it ties up the enzyme that breaks medicine down; in a body that has drunk for years, that same enzyme is instead raised. The same drink swings the thing in opposite directions. On top of that it irritates the lining of the stomach and intestines and disrupts absorption. While you are taking herbal medicine, it is best to cut back.

Grapefruit.
You will find this surprising. Grapefruit presses down the enzyme in the wall of the intestine that would have broken the medicine down on the way in. It drops by nearly half within a few hours, and the effect runs on for about a day. What used to be filtered at the door comes straight through, and more of it stays than expected. This is well known with hospital medicines, and herbal medicine has the same doorway.

Caffeine.
For people whose heart races or who cannot sleep, or whose autonomic nervous system has become sensitive, coffee undoes the treatment. Often coffee is a stronger signal than the medicine.

Cold foods and greasy foods.
For people whose digestive system has weakened, they are a burden. In a treatment whose goal is absorption, eating things that hinder absorption makes it difficult.

The radish story runs longer — the seed and the root are not the same

This is where the real substance of this piece begins.

"Radish scatters the energy of herbal medicine." The old records put it plainly: ginseng dislikes radish seed.

But there is a fork here. What the old records name is the seed of the radish. What you eat at the table is the root. Same plant, different part used as medicine.

On the seed, the old saying was right.

Recent experiments have actually reproduced the pairing. Decoct radish seed together with ginseng and less ginseng saponin comes out of the pot in the first place. In cell work, radish seed raised the rate at which ginsenosides were pumped back out, lowering absorption. In a chronic-fatigue model, ginseng's power to lift energy weakened — and the more radish seed, the more it weakened.

A pairing written down as "disliked" some centuries ago turns out to be visible at the level of how much saponin leaves the herb and how fast a cell pumps it out. I find that sort of thing a pleasure.

There is one more turn. In the same work, acute fatigue showed no difference at all, and the radish seed actually reduced ginseng's tendency to raise heat. So it is less a "bad pairing" than a pairing where each turns the other back. Where the old physicians could only write "dislikes," we can now attach the conditions.

On the root, we still don't know.

But none of this can be carried straight over to the radish in your soup. I have not seen data showing that eating radish root alongside ginseng weakens the medicine. A seed decocted as medicine and the radish in a bowl of soup differ in amount, in part, and in how concentrated the compounds are.

The folk taboo speaks of the root. And that part has not been checked.

Mung beans.
The saying that "mung beans dissolve the energy of the medicine" is also common. It probably comes from the old notion that mung beans detoxify.

Here I could find nothing in either direction. There is no evidence that a bowl of mung bean porridge renders herbal medicine powerless, and none that it doesn't.

Pork.
There are records telling you to avoid it with certain prescriptions. In today's language, the point reaches as far as greasy food burdening the digestive system.

So how did the radish on the table end up on the list?

Herb names and food names slide into one word easily enough. "Be careful of radish seed," said in the consulting room, would not have taken long to become "be careful of radish" on the walk home.

Two more things likely settled on top of it.

It was an age without refrigerators. The warning may have carried, alongside, an instruction to avoid what spoils easily and upsets the stomach. While taking medicine, take care of your body.

And when there is something to observe, people treat the matter earnestly. A taboo is also a device that keeps medicine from being handled carelessly.

In the consulting room, here is how I put it

Nothing terrible happens because you had radish soup. A bowl of mung bean porridge does not collapse the treatment. Eating anxiously because of it is, if anything, more harmful.

Keep to the ones whose reason can be named — alcohol, grapefruit, coffee, and things that burden digestion. For the rest, eat with an easy mind. You are not going to eat radish seed as a side dish. Getting that pairing right is my work, and I look at it when I compose the prescription.

But if you eat something and your body changes, do tell me. That is an observation that came out of your own body, and the old taboos were probably built the same way.

What I ask about before food

We have spent a while on food, but the thing I ask about first in the consulting room is something else.

The other medicine you are taking.

What you take alongside can change what needs adjusting on the herbal side. Herbal medicine containing licorice, for instance, can lower potassium when it meets a diuretic. (A medicine's effect and its side effect come from the same place) Known in advance, this is easy to steer around. Unknown, it isn't.

Ask me about radish by all means — just tell me about the medicine too.

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There is a reason I spent so long on the radish. Between "it's an old saying, so there's nothing to it" and "it's an old saying, so keep to it" lies a far more interesting place. A pairing written down as disliked centuries ago shows up in how much saponin leaves the herb — and that same story has not yet reached the radish in your soup. Both of those are true at once.

The ones the explanation has reached, I keep for you with a reason attached. The ones it hasn't, I leave as they are. In time, a few more of them will get a name.

Until then, two things are enough. Tell me what you are taking. And tell me when your body changes.

References

• Pairing radish seed with ginseng weakened ginseng's energy-restoring effect in a chronic fatigue model, more so at higher radish-seed ratios (no difference in acute fatigue) — Journal of Ethnopharmacology, 2022
• Grapefruit juice reduced intestinal CYP3A4 by up to 47% within four hours, raising drug bioavailability, with the effect lasting up to a day — Nutrition Journal, 2007
• Glycyrrhizin metabolites from licorice inhibit 11β-HSD2, leading to hypokalaemia, oedema and hypertension, with increased risk when combined with potassium-wasting diuretics — Frontiers in Nutrition, 2021

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