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.

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. Some were left with severe loss of kidney function, and the number of confirmed patients later passed one hundred.

When the cause was traced, it emerged that the material that should have been used had been replaced by a different one with a similar name. It happened because the two share their Chinese-character names. That material contained a component called aristolochic acid. This component directly damages the renal tubules. Several countries now ban its use.

This is not a matter under debate. Nor is it 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 — the United States in 2001, Taiwan and Hong Kong in 2003–2004, China in 2004, Korea in 2005, and the European Union in 2011.

In Korea, on 1 June 2005 the Food and Drug Administration halted the manufacture, import, sale, and use of cheongmokhyang and madueryeong, which contain aristolochic acid, and that same year these materials were struck from the pharmacopoeia of herbal materials. Gwangbanggi, the cause of the Belgian incident, and gwanmoktong cannot be used domestically either.

So that incident was not a story of "herbal medicine ruins the kidneys" but of "a specific component ruins the kidneys." In fact, in the Balkans the same plant, growing mixed into wheat fields and entering the flour, caused the same disease with no connection to herbal medicine at all. The problem is not the category "herbal medicine" but that component.

Still, Things Remain to Watch

The story does not end just because that material was withdrawn. There are a few more routes that can burden the kidneys, and I look at them when I prescribe.

First, licorice. Licorice is the most 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, something whose contents have not been confirmed. Where there is no testing and no record, I have no ground on which to make a judgment at all.

Then What About Everyday Herbal Medicine?

There is a review that gathered 59 clinical studies of herbal medicine carried out in Korea. When the studies that looked at kidney-function markers before and after taking a decoction were gathered and analyzed, no clear change appeared. In a pooled analysis of 6 randomized controlled trials covering 407 people, there was likewise no difference in kidney-function markers between those who took herbal medicine and those who took placebo.

But let me be clear about the range of this material. It looked at a few standardized prescriptions over a relatively short period. So it should be read not as "all herbal medicine is safe" but as it was so under the conditions studied.

There is one more interesting piece. When 25,000 patients with chronic kidney disease were followed in Taiwan, the risk of end-stage renal failure was observed to be lower in the group that used herbal medicine. But in the same study the results diverged depending on the family of prescription. It is early to speak of cause in an observational study, but I think this part in fact shows the character of this medicine: herbal medicine is not a single substance but a question of what is used and how.

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, or if you are tired for no reason with no appetite and are itchy — a nephrology consultation and testing come before starting herbal medicine. All the more so if you have already been diagnosed with chronic kidney disease or are on dialysis. And with any herbal medicine, if you swell or your urine becomes abnormal while taking it, stop immediately and let me know.

What I say instead of "it is safe"

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 watch, and I use them knowing that.

This, I think, is what knowing a medicine means. Where it came from, what path it takes through the body, and what to watch for in whom.

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References

• The course of the Belgian incident and regulation across countries — a review of aristolochic acid nephropathy — Kidney Research and Clinical Practice, 2023
• Liver and kidney function across 59 clinical studies of herbal medicine in Korea — Journal of Ethnopharmacology, 2024
• Pooled analysis of 6 randomized controlled trials, 407 people — herbal medicine and kidney function — Pharmaceuticals, 2024

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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)