The Same Herb, Different People, Different Results — Why Your Gut Decides

I give the same prescription, and one person tells me they changed within a week, while another sees little response after a month. Same medicine, same dose — so why does this happen?

You could say it's because their constitutions differ. That isn't wrong. But I want to look a little more concretely at what is actually inside that word "constitution." Much of it is decided in the gut.

Herbal medicine does not act in the form you swallow

There is a fact that isn't widely known. Many of an herb's active compounds exist in a form with a sugar attached. In that state, the body cannot use them well.

These compounds simply pass through the stomach and small intestine. Only when they meet the microbes living in the large intestine does the sugar get cleaved off, turning them into an active form the body can absorb.

Put another way: herbal medicine is a medicine whose door opens only when the microbes in your gut turn the key.

So here is what follows

Once you accept this, several things explain themselves naturally.

For someone whose gut is not in good shape, even a good medicine cannot show its strength. If the microbes that would turn the key are insufficient or disordered, the compounds pass through without ever being activated.

Someone who has recently used antibiotics for a long time may respond differently. Antibiotics do not selectively remove only the bacteria causing disease.

Even the same person responds differently at different times. Gut condition is not fixed; it shifts with diet, stress, and sleep.

This is why I always ask about digestion first

To someone who came in for back pain, for insomnia, for cold hands and feet — I almost without exception ask about their digestion and bowel movements.

First-time patients find this puzzling. "I came about my back — why are you asking about my stool?"

There are two reasons.

First, I am checking the conditions under which the medicine will work. No matter how precise a prescription I design, in a poor gut the medicine cannot do its part. In that case I have to change the order: instead of going straight for the target treatment, I place a formula that first settles the gut. It looks like a detour, but it is actually the shortcut.

Second, the gut itself is often the cause. The gut is where the most immune cells in the body are gathered, and it is densely connected to the autonomic nervous system. That the belly hurts when we're tense, and sleep grows shallow when the gut is bad, is no coincidence.

Then should I just take probiotics?

It may help. But rather than putting bacteria in, making an environment in which those bacteria can live lasts longer. What you eat, how well the digestive tract moves, and whether the autonomic nervous system is settled — these all work together.

In summary

• Many of an herb's active compounds must pass through the metabolism of gut microbes to be activated
• So the state of the gut governs the effect of the medicine
• A slow response may be not because the medicine is bad, but because the conditions for the medicine to awaken are lacking
• This is why, whatever symptom brings you in, I examine digestion and the gut first

It may be the order, not the herb

This explanation is substantially supported by research, though it does not fully account for every difference between individuals. Genetic metabolic capacity, timing of the dose, and the stage of the illness all play a part.

Still, when a response is slow, I hope you won't rush to conclude "this medicine must not be right for me." The problem may not be the medicine, but the order. Finding that order together is my work.

Research referenced

The core of this article — the account that many of an herb's active compounds must pass through the metabolism of gut microbes to be activated — is supported by the following review papers.

• On how gut microbial enzymes transform natural-product compounds into active metabolites: Potential roles of gut microbes in biotransformation of natural products: An overview, Frontiers in Microbiology (2022). Read the source
• As a representative example, how ginseng saponins are converted by gut bacteria into an absorbable active form (compound K): A review of biotransformation and pharmacology of ginsenoside compound K, Fitoterapia (2015). Read the source

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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)