The Medicine Your Gut Has to Switch On — Following a Single Herb, Gardenia, All the Way Through

"Medicine works differently in different people" — I have written that many times. (Why does the same herb work differently in different people)

But that sentence, by itself, explains nothing. To be an explanation, you have to say where, what, and how it divides.

So today I will pick one herb and follow it all the way through. Gardenia — the yellow that colours kimchi radish, the fruit behind that yellow.

Follow this one herb, and almost everything about how I see the body and medicine comes out.

First, gardenia barely works as it is

The main component of gardenia is a substance called geniposide.

But this substance is in a locked form. More precisely, the active substance has a sugar attached to it. A form with sugar attached like this is called a glycoside.

While the sugar is attached, this substance does little inside the body. It is not well absorbed either.

So when does this become medicine?

When it goes down to the gut and the bacteria living there strip off that sugar.

An enzyme the bacteria carry, beta-glucosidase, cuts the sugar away. The lock opens and it becomes an active substance called genipin. What the body actually responds to is this genipin.[1]

This is not guesswork; it shows in numbers. The proportion absorbed when gardenia components are taken as they are is low, but absorption rises several-fold once it passes through gut bacterial metabolism — confirmed in animal studies.[1] The key that opens the lock is in the gut.

What switches the medicine on is not the medicine. It is the bacteria living in that person's gut.

And so I make this prediction

If the mechanism is like this, a conclusion follows. And that conclusion has to be something checkable in the consultation room. An explanation you cannot check is not an explanation but a story.

In people whose gut bacteria are depleted, this medicine works less.

• Those who recently took antibiotics for a long time
• Those whose gut is worn from long-standing diarrhoea
• Those whose gut is sensitive, so absorption itself wavers

For these people, the same medicine at the same dose brings a different response. I do not want to file this away as "that person's constitution." If the bacteria that open the lock are short, the medicine does not switch on. That is the reason.

So for such people I look at the gut first. I make the conditions for the medicine to work. Reverse the order and even a good remedy runs in vain. (Immunity is decided in the gut)

This is what I mean by environment. What decides whether a medicine works is, in the end, environment too.

Once switched on, this substance doesn't do just one thing

This is the part I consider important when explaining herbal medicine through modern pharmacology.

Genipin does not go to one place and do one thing. It touches several axes of the body at once.

Axis	What it does	Weight of evidence
Immunity · inflammation	Presses the central switch that turns on inflammatory signalling (NF-κB), reducing excess signalling molecules [5]	Mostly lab · animal
Metabolism · mitochondria	Acts on the channel through which mitochondria leak energy as heat (UCP2) [6]	Lab evidence · unconfirmed in humans
Bile · liver	Pushes bile and bilirubin along so they do not pool	Animal · consistent with traditional use
Oxidation · circulation	The pigment that makes gardenia yellow (crocin) itself reduces oxidative stress	Lab · animal

That the yellow pigment is not merely colour but one of the substances producing the effect — this is the kind of thing I find interesting. What you can see is what is acting.

One herb touches four axes at once. And a single herbal formula contains several such herbs.

I see this not as herbal medicine's weakness but as its nature. Long-standing illness rarely has just one axis broken. Several axes waver together. To turn such a state around, pushing several axes a little at once can be better than pushing one axis hard.

That said, I will not use this as a boast. It is precisely this nature that makes herbal medicine hard to prove. It is difficult to tell what did what. I acknowledge this weakness.

So I set a duration

If you've followed the mechanism this far, why I decide the stopping point together with you follows naturally.

Gardenia calls for caution when taken over many years without a break. Changes in the veins going to the gut have been reported in people (mesenteric phlebosclerosis). In a Japanese survey of people found to have it, the cumulative amount taken was generally over 5,000g, and the average duration was around 11 years.[2][3] In those who took less, and for shorter periods, it was not readily found.

The crux is not "amount" but "duration." Taking it for a few weeks and taking it for years without a break are different stories.

This is why, when I start a medicine, I decide with you when to stop. Not vague caution — there are numbers behind it.

Amount is the same story

In animal studies, the amount at which a burden began to appear was a range far higher than the amount used to seek an effect.[4] So "setting the amount" is not vague care either — it is a line with numbers behind it.

And here is where I find this herb interesting. The substance that creates the burden is also genipin. The very substance I just described as calming inflammation and moving bile along.

The substance that produces the effect, and the substance that becomes a burden when taken too far, are the same. (Benefit and harm come from the same place)

It is not a coincidence. It comes from the same place, by the same mechanism, differing only in amount and time. So what makes something safe is not the medicine's origin but the amount, the duration, and that person's condition. This is why I do not use the phrase "natural, therefore safe."

And so this is how I use it

Because I know this mechanism, I fix a few things when I use gardenia.

I set the amount. It is not a medicine that works better the more you use. Past a certain line the benefit stops and only the burden rises. (Is strong medicine good medicine)

I set the duration. At the start, we decide together when to stop. "Keep going until it gets better" is not a plan. As you have just seen, the risk with this herb comes from long use. (When should medicine be stopped)

I look at the liver. Those whose liver is already weak, those whose liver values have been up, those taking other medicines that burden the liver — for them I judge differently.

I look at the gut too. As I said, this medicine needs the gut to switch it on.

What I would like to say

The reason I write out the components and mechanism in this much detail is that I believe you have a right to know what a medicine does in your body.

But knowing and judging alone are different things.

• Even the same herb differs depending on how it was processed. That is why I use standardised material with a traceable record. (Where did that herb come from)
• How much, and for how long, depends on the person's condition.
• And as I just said, this medicine's risk comes from the same place as its effect. Use much of it for long, and the risk grows accordingly.

It is a pretty fruit that dyes things yellow, and it is used in food. So it looks all the more harmless. Looking harmless does not make it harmless. It calls for caution.

When you should go to the hospital first

Since I have talked about the liver and bile, I must say the following. Whatever herbal medicine you are taking, if the below appear, stop the medicine and go to hospital at once.

• The whites of the eyes or the skin turn yellow
• Urine turns dark like cola, stool turns pale
• The upper right abdomen hurts or feels heavy
• Severe fatigue, appetite dropping away, continued nausea
• Itching all over

And if you are someone who has taken herbal medicine over many years, do not let the following pass either.

• The belly hurts repeatedly, feels bloated, diarrhoea is frequent
• These symptoms continue for months or more

They look like common digestive symptoms, but the change in the gut's veins I mentioned earlier begins just like this. Be sure to tell your clinician about your long history of taking it. Without that information, diagnosis is delayed.

None of these is "part of getting better." (On the word "healing crisis" — I said the same there.)

And those with liver disease, or whose liver values are raised, please tell me before starting herbal medicine. I do not judge without that information.

To be honest with you

Let me separate out how far I am certain in this article, and where the uncertainty begins.

Established: That geniposide is a glycoside, and that gut bacterial enzymes must strip the sugar for it to become genipin. This is well confirmed. So is the fact that gut bacteria differ from person to person.

At the lab · animal stage: That genipin presses the inflammation switch, acts on the mitochondrial channel, and reduces oxidative stress — mostly confirmed in cells and animals. Whether the same happens in people at the same magnitude has not been confirmed.

Where reports have accumulated in humans: Mesenteric phlebosclerosis with long-term use. This was confirmed not in cells or animals but in humans, so it is the part I put weight on in this article. For liver burden with high-dose, long-term use, case reports and animal studies exist together.

My own interpretation: That "pushing several axes at once is favourable for long-standing illness," and that "the reason a medicine does not work can be found in the gut's condition" — this is a frame I built in the clinic. It is not yet proven.

These four must not be mixed. Mixed together they sound more plausible, but plausible and true are different things.

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I followed gardenia all the way through.

There is a locked component, there are bacteria that open it, the opened substance touches several axes at once, and in one of those axes benefit and burden come out together.

Herbal medicine does not work because it is mysterious. It works along concrete paths like this. And along the same concrete paths, it calls for caution.

I look at this path and use it. Knowing the path lets me set the amount and the duration.

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Evidence — what this article stands on

The numbers above point to the materials below. Please read them together with the four stages in "To be honest with you." What has evidence and what I built in the clinic are different things. The evidence concerns the components, the mechanism, and the risk; how to use them is my judgement.

1. Effects of intestinal microbiota on the bioavailability of geniposide in rats. Journal of Agricultural and Food Chemistry, 2014. — That geniposide must pass through gut bacterial metabolism to be absorbed and activated, and that its absorption varies greatly with the gut's condition. https://pubs.acs.org/doi/10.1021/jf502557f
2. Nagata Y, et al. Involvement of herbal medicine as a cause of mesenteric phlebosclerosis: results from a large-scale nationwide survey. Journal of Gastroenterology, 2016. — Japanese nationwide survey (222 patients). Reports an association between long-term use of gardenia-containing herbal medicine and mesenteric phlebosclerosis. https://link.springer.com/article/10.1007/s00535-016-1218-9
3. Nagata Y, et al. Total dosage of gardenia fruit used by patients with mesenteric phlebosclerosis. BMC Complementary and Alternative Medicine, 2016. — In those found to have it, cumulative gardenia intake was generally about 5,000g or more, average duration about 11 years. https://pmc.ncbi.nlm.nih.gov/articles/PMC4940942/
4. Dose-related liver injury of geniposide associated with the alteration in bile acid synthesis and transportation. Scientific Reports, 2017. — Liver injury appeared at doses far higher than those used to seek an effect, associated with disturbance of bile acid metabolism. https://www.nature.com/articles/s41598-017-09131-2
5. Genipin alleviates LPS-induced acute lung injury by inhibiting NF-κB and NLRP3 signaling pathways. International Immunopharmacology. — Lab · animal evidence that genipin presses inflammatory signalling (NF-κB · NLRP3). https://www.sciencedirect.com/science/article/abs/pii/S1567576916301989
6. Genipin-induced inhibition of uncoupling protein-2. PLoS ONE, 2010. — That genipin acts on mitochondrial UCP2. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013289

Of the above, what was confirmed directly in humans is 2 and 3 (mesenteric phlebosclerosis). 1, 4, 5 and 6 are mostly cell · animal stage evidence. I have stated this difference in weight in the body of the article.

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