The Claim That Herbal Medicine Damages the Kidneys

"I heard that taking herbal medicine wrecks your kidneys."

I dealt with the misconception about the liver earlier. (Where Did the Idea That Herbal Medicine Is Bad for the Liver Come From?) Today it is the kidneys.

And this story is different from the liver. On the kidney side, there was an incident that actually happened. I think it is right to speak of it without concealing it.

What Actually Happened

In the early 1990s in Belgium, women who took medicine for the purpose of weight loss suffered successive cases of kidney failure. Not a few of them went as far as dialysis or kidney transplantation.

When the cause was traced, it emerged that the wrong herbal material had been mixed in during the compounding process. That material contained a component called aristolochic acid. This component damages the renal tubules and causes fibrosis, and a link with urinary-tract cancer was later confirmed as well. The International Agency for Research on Cancer classifies this substance as a clear carcinogen.

This is not a matter under debate but an established fact. It is not something a practitioner of Korean medicine can deny.

So Where Do Things Stand Now?

After this incident, countries regulated the herbal materials containing that component.

Korea did the same. In 2005, materials containing aristolochic acid (Aristolochia fangchi / gwangbanggi, Aristolochia manshuriensis / gwanmoktong, Aristolochia debilis / madueryeong, Aristolochia / cheongmokhyang, and others) were removed from the pharmacopoeia. The herbal materials used through normal channels at clinics today do not include these materials. Their distribution itself is prohibited.

In other words, that incident was not a story of "herbal medicine ruins the kidneys" but of "a specific toxic material ruins the kidneys," and that material was withdrawn 20 years ago.

But I Do Not Stop Here

If I ended with "that material is no longer used, so herbal medicine is safe," I would consider myself dishonest.

Because there are still other routes that can burden the kidneys.

First, licorice. Licorice is a common material and is known as gentle, but in excess it makes the body hold on to sodium and water and send out potassium. Blood pressure rises, swelling appears, and in severe cases muscles go weak and arrhythmia can occur. It requires particular caution in those with weak kidneys and those taking diuretics. (Herbal Medicine Has Side Effects Too — The Story of Licorice)

Second, cases where kidney function is already reduced. The kidney is the organ that filters medicine out. When that function is reduced, even an amount that would normally cause no problem accumulates in the body. This is not a problem unique to herbal medicine but a principle that applies to all drugs.

Third, medicine of unknown origin. This is what I worry about most. I will address it separately below.

The Real Danger Is Not "Herbal Medicine" but "Medicine of Unknown Origin"

The herbal materials prescribed at a clinic are standardized products. Only those produced and inspected according to nationally set standards may be used, and they must pass heavy-metal and pesticide-residue testing. A record remains of which material came from where.

But there are things outside these channels.

• Things bought directly at a market or online and decocted at home
• Pellets and powdered medicine of unknown origin received while traveling or through an acquaintance
• Things mixed together on the claim that they are "good for the body"

There is no testing here. There is no way for me to verify what went in or how much. In fact, kidney-damage accidents happen far more often through these routes.

So I tell my patients this: "It is not herbal medicine that is dangerous; it is not knowing who put in what that is dangerous."

Then How Do You Check?

Before prescribing to someone who has reason to worry about the kidneys, I check a few things.

I look at kidney-function values. If you have test results already, I ask you to bring them. If you have none and have risk factors, I recommend testing.

I check all the medicines you are taking. Blood-pressure medication, diuretics, painkillers, diabetes medication. Those who have taken painkillers for a long time, in particular, may already have kidneys under burden.

I review the materials in the prescription. I check whether materials that affect electrolytes, like licorice, are all right for this patient and whether the amount is appropriate.

I set the duration. I use it only as much as needed and then stop. (When Should You Stop the Medicine?)

Cases Where You Should Go to a Hospital First

• If your urine output has noticeably decreased, or your urine is heavily foamy
• If your face or legs are swelling
• If your blood pressure has risen suddenly
• If you are tired for no reason, have no appetite, and are itchy
• If you have already been diagnosed with chronic kidney disease, or are on dialysis

In these cases, a nephrology consultation and testing come before starting herbal medicine. And with any herbal medicine, if you swell or your urine becomes abnormal while taking it, stop immediately and let me know.

Finally

I do not say "herbal medicine is safe." That statement explains nothing.

Instead I say this: There was a dangerous material, and it was withdrawn. There are still materials to be careful with, and I use them knowing that. And medicine whose contents have not been verified calls for caution.

Being able to say this much—that, I believe, is what it means to truly know medicine.