Iberogast for Acid Reflux: Does STW-5 Actually Work?

Partly — but not in the way most people hope. Iberogast (STW-5) is a nine-herb liquid extract with genuinely respectable clinical evidence, and almost all of it is for functional dyspepsia: the fullness, early satiety, bloating and upper-belly discomfort cluster. It is not licensed for, or primarily tested on, acid reflux. The one trial that looked directly at reflux symptoms was small, and it missed its main target while hitting a few secondary ones.

That said, the reflux angle isn’t nonsense. STW-5 acts on gastric tone and emptying, and there’s early evidence it dampens oesophageal hypersensitivity — which is exactly the mechanism that leaves some people feeling burning and regurgitation despite unremarkable acid levels. So it may help a specific subset. It just isn’t an acid-reflux drug.

There’s also a safety story you need before you buy a bottle: the original formula contains greater celandine, a herb linked to rare but serious liver injury. That’s why a reformulated version exists. Below is the mechanism, the actual trial data, who might reasonably benefit, and what to watch for.

Key Takeaways

• Iberogast (STW-5) has solid randomised-trial evidence for functional dyspepsia, not for GERD or LPR.
• The only dedicated reflux trial — 18 dyspeptic patients with reflux symptoms — missed its primary endpoint but showed lower GERD and regurgitation subscale scores versus placebo.
• In the subgroup with pH-confirmed GERD, STW-5 significantly reduced total acidic reflux events; in those with oesophagitis, it took longer to perceive acid.
• The proposed mechanism is reduced oesophageal hypersensitivity plus better gastric accommodation and antral motility — not acid suppression.
• The original nine-herb formula contains greater celandine, which carries a real, documented risk of idiosyncratic liver injury, including a case requiring transplantation.
• STW 5-II (sold as Iberogast Advance or Iberogast N) drops celandine, angelica and milk thistle and has its own positive dyspepsia trials.
• It contains peppermint and alcohol — both of which can relax the lower oesophageal sphincter and aggravate reflux in some people.
• Best thought of as a possible add-on if dyspepsia and reflux overlap, not as a standalone reflux treatment.

What Iberogast Actually Is

Iberogast is a fixed-combination herbal liquid developed in Germany in the 1960s and sold in much of Europe as a licensed medicine rather than a supplement. The original preparation, STW-5, contains nine hydroethanolic plant extracts: bitter candytuft (Iberis amara, the “Ibero” in the name), peppermint leaf, chamomile flower, liquorice root, caraway fruit, lemon balm leaf, angelica root, greater celandine and milk thistle fruit.

The usual dose is 20 drops in a little water, three times a day with meals. It’s a bitter, alcoholic tincture — the taste puts some people off immediately.

The design logic is multi-target. Rather than blocking one pathway hard, the way a PPI blocks the proton pump, each extract nudges a different part of the gut: smooth muscle, enteric nerves, mucosal inflammation, gas handling. A 2026 review in Neurogastroenterology & Motility summarises the preclinical work and concludes the ingredients hit multiple mechanisms relevant to symptom generation in disorders of gut–brain interaction Annaházi et al., Neurogastroenterology and Motility, 2026. That’s a fair description — and also a reminder that “multi-target” is easier to demonstrate in a lab than in a person.

The Evidence for Dyspepsia Is Genuinely Good

This is where Iberogast earns its reputation, and it’s worth being clear that the data is better than most things sold for digestion.

A meta-analysis pooling raw data from three placebo-controlled trials found STW-5 significantly more effective than placebo at reducing the severity of the most bothersome gastrointestinal symptom, with adverse events no different from placebo Melzer et al., Alimentary Pharmacology and Therapeutics, 2004. A separate trial found no significant difference between STW-5 and cisapride, a prokinetic drug since withdrawn in many countries for cardiac safety reasons.

The reformulated six-herb version has been tested more recently. An eight-week, double-blind, multicentre trial in 272 patients with functional dyspepsia found a response rate of 61.2% with STW 5-II versus 45.1% with placebo Vinson et al., JGH Open, 2024. A patient-level meta-analysis of four randomised trials covering 613 patients confirmed significant improvements in the overall symptom score and in fullness, early satiety and epigastric pain, with no safety signal versus placebo Andresen et al., Digestion, 2024.

Note what all of that is measuring: fullness, early satiety, epigastric pain. Not heartburn. Not regurgitation. Not throat symptoms. If your problem is functional dyspepsia, this is legitimately one of the better-supported options. If your problem is reflux, you’re borrowing evidence from a different condition.

The One Trial That Looked at Reflux

In 2024, a group at Amsterdam UMC published the study that actually asks our question. It was a double-blind, randomised, placebo-controlled crossover trial in 18 patients who had both functional dyspepsia and reflux symptoms. After four weeks on each treatment, patients underwent an oesophageal acid perfusion test and 24-hour pH-impedance monitoring.

The primary outcome — the total Reflux Disease Questionnaire score — showed no significant difference. That’s the headline, and it should temper expectations.

But the secondary findings were more interesting. The “gastroesophageal reflux” and “regurgitation” subscale scores were both significantly lower after STW-5 than placebo. In the subgroup with pH-metry-confirmed GERD, STW-5 significantly reduced the total number of acidic reflux events. And in patients with reflux oesophagitis, the median lag time before they perceived acid during the perfusion test increased — meaning acid was in contact with the oesophagus for longer before it registered as pain. The authors concluded there were “some indications” of benefit, with reduced oesophageal hypersensitivity as the likely mechanism, and called for larger studies Oude Nijhuis et al., Journal of Neurogastroenterology and Motility, 2024.

Eighteen patients is small. A missed primary endpoint with positive secondaries is exactly the pattern that sometimes turns into a real effect in a bigger trial and sometimes evaporates. So: promising, unproven.

Why It Might Help — The Mechanisms Worth Understanding

Three things are plausibly going on, and none of them involve reducing stomach acid.

Reduced oesophageal hypersensitivity

This is the mechanism the Amsterdam group favoured, and it matters more than it sounds. A large group of reflux patients don’t have unusually high acid exposure — they have an oesophagus that reports normal or near-normal amounts of acid as pain. If a treatment raises that perception threshold, symptoms improve without acid changing at all. That’s the same territory as neuromodulators used for reflux hypersensitivity, though Iberogast is a far gentler intervention.

Better gastric accommodation and emptying

STW-5 relaxes the upper stomach (fundus) while increasing motility in the lower stomach (antrum). In practical terms that means the stomach can take a meal without the pressure spike, and then move it along. A stomach that empties sluggishly is a stomach under pressure, and pressure is what drives reflux across the junction. If you’ve ever noticed reflux getting worse specifically after large meals, this is why delayed gastric emptying and reflux travel together so often.

Less gas and distension

Carminative herbs like caraway, peppermint and chamomile reduce gas trapping and bloating. Since gastric distension is a trigger for transient lower oesophageal sphincter relaxations — the single biggest cause of reflux events — anything that reduces distension can reduce reflux indirectly. It’s the same logic behind why overeating triggers reflux so reliably.

Notice the shape of all three: they work upstream of the reflux event, on pressure, motility and perception. That’s the same territory the Wipeout Diet Plan works in, which is why the two aren’t really competitors — a herbal tincture nudges those mechanisms, while changing what and how you eat moves them properly.

The Liver Safety Problem You Need to Know About

This is the part most articles skip, and it’s the single most important thing on this page.

Greater celandine (Chelidonium majus) is one of the nine herbs in the original STW-5. It contains isoquinoline alkaloids and has been repeatedly linked to idiosyncratic herb-induced liver injury — typically a hepatocellular pattern with jaundice and markedly raised liver enzymes, appearing anywhere from one to six months into use. A literature review assessing celandine’s hepatotoxicity concluded that, given the absence of substantial proven benefit from the herb itself, the risk-to-benefit ratio for products containing it should be considered negative Pantano et al., European Review for Medical and Pharmacological Sciences, 2017. The NIH’s LiverTox database maintains a dedicated record on the herb LiverTox, National Institute of Diabetes and Digestive and Kidney Diseases, 2019.

Iberogast specifically has case reports attached to it, including one published in the American Journal of Gastroenterology describing severe hepatotoxicity that progressed to liver transplantation Sáez-González et al., American Journal of Gastroenterology, 2016. European regulators required strengthened liver warnings on the product in 2018.

To be proportionate: these reactions are rare, idiosyncratic, and not dose-related in any predictable way. Millions of bottles have been sold. But “rare and unpredictable” is not the same as “not your problem,” and the reaction can be severe. Two practical conclusions follow.

First, if you use it, prefer the reformulated version. STW 5-II — marketed as Iberogast Advance or Iberogast N depending on the country — contains six herbs and has dropped greater celandine, angelica root and milk thistle. It’s the version most of the recent trial evidence is based on anyway. Check the ingredient panel rather than trusting the brand name, because both formulations are still on shelves in different markets.

Second, stop immediately and get liver function tested if you develop jaundice, dark urine, pale stools, itching, right-upper-quadrant pain or unexplained fatigue and nausea. Don’t wait to see if it passes.

The Ingredients That Can Make Reflux Worse

Here’s the irony: two things in Iberogast are classic reflux aggravators.

Peppermint. Menthol relaxes smooth muscle, and that includes the lower oesophageal sphincter. Peppermint is on essentially every reflux trigger list for exactly this reason, and it’s one reason peppermint tea is a mixed bag for reflux. The dose in 20 drops is small, but if you’re someone whose lower oesophageal sphincter is already the weak link, it’s a real consideration.

Alcohol. It’s an ethanolic extract. The absolute amount per dose is tiny, but alcohol also relaxes the sphincter, and some people with sensitive oesophagi report a burning sensation from the tincture itself.

Liquorice. The original formula uses whole liquorice root, not the deglycyrrhizinated form. Glycyrrhizin in meaningful quantities can raise blood pressure and lower potassium. At Iberogast doses this is unlikely to matter, but it’s worth knowing if you already take DGL for reflux or have hypertension.

Who Might Reasonably Try It

Based on where the evidence actually sits, Iberogast makes most sense if:

• Your dominant symptoms are dyspeptic — fullness after small meals, early satiety, upper-belly discomfort, bloating — with reflux as a secondary complaint.
• You’ve been told your endoscopy and pH study are normal, and hypersensitivity or motility is the working explanation.
• You want a low-intensity add-on alongside dietary work, not a replacement for it.

It makes much less sense if:

• You have erosive oesophagitis, Barrett’s, or documented high acid exposure — those need proper treatment, not a herbal bitter.
• Your symptoms are throat-dominant. There’s no LPR evidence for Iberogast at all, and LPR symptoms are driven largely by pepsin, which nothing in this formula addresses.
• You have any liver condition, or take other hepatotoxic medication.
• You’re pregnant or breastfeeding — it isn’t recommended.

If you do try it, give it four to eight weeks at the standard dose, keep a simple symptom diary, and be honest with yourself about whether anything actually changed. Herbal products attract a lot of wishful interpretation.

Where It Sits Against the Alternatives

For pure reflux, better-evidenced options exist. Alginates form a physical raft over the stomach contents and have direct reflux trial data behind them — alginates for acid reflux are a more logical first stop if regurgitation and burning are the main issue. Prokinetics target emptying more forcefully than any herb will. And acid suppression, whatever its limitations for throat symptoms, remains the right tool for genuine acid-driven oesophageal damage.

Where Iberogast is distinct is the overlap zone — the very common patient who has both dyspepsia and reflux and has been bounced between diagnoses. That’s a real group, and it’s the group the Amsterdam trial was studying.

Conclusion

Iberogast is a well-made herbal product with real evidence — for the wrong condition, if reflux is what you’re treating. Its dyspepsia data is strong; its reflux data amounts to one 18-patient crossover trial that missed its primary endpoint and produced some encouraging secondaries. It may reduce how intensely your oesophagus reports acid, and it may ease the gastric pressure that drives reflux events, but it does nothing to acid itself and nothing to pepsin. Add the greater celandine liver risk in the original formula, plus peppermint and alcohol in a product aimed at reflux sufferers, and it becomes a reasonable experiment rather than a foundation.

Because the foundation has to be the thing that reduces how often you reflux in the first place. That’s precisely what the Wipeout Diet Plan is built to do — a structured, mechanism-first approach that works on meal size and composition, gastric pressure, timing and trigger load, so the reflux events themselves become less frequent instead of merely feeling less sharp. I originally designed it around LPR and silent reflux, the stubborn throat-based form where people end up trawling supplement shelves out of desperation, but since it targets the same underlying mechanisms it works just as well for GERD and everyday heartburn. And if you want somewhere concrete to start this week, the Wipeout Food Reference Guide is the essential companion — every food and drink that’s safe for acid reflux and LPR, with their actual pH values, so you’re working from data rather than guesswork.

Use Iberogast if the dyspepsia side of your symptoms is genuinely bothering you, choose the celandine-free version, and treat any improvement in reflux as a bonus rather than the plan.

Frequently Asked Questions

Does Iberogast help acid reflux?

Only indirectly, and the evidence is thin. One small crossover trial found no significant difference in overall reflux questionnaire scores, but did find lower GERD and regurgitation subscale scores and fewer acidic reflux events in the confirmed-GERD subgroup. It is not an acid-reducing medicine and isn’t licensed for reflux.

How long does Iberogast take to work?

Trials typically assess at four and eight weeks, and improvements are usually measured over that window. Some people notice a difference in bloating and fullness within a week or two. If nothing has changed after eight weeks, it isn’t going to.

Is Iberogast safe for the liver?

The original nine-herb formula contains greater celandine, which is linked to rare but occasionally severe idiosyncratic liver injury, including a documented case leading to transplantation. The reformulated STW 5-II versions (Iberogast Advance / Iberogast N) omit it. If you use the original, stop and get tested at the first sign of jaundice, dark urine or unexplained fatigue.

What’s the difference between Iberogast and Iberogast Advance?

Iberogast Advance (STW 5-II) contains six herbs — bitter candytuft, peppermint, chamomile, liquorice, caraway and lemon balm. It drops greater celandine, angelica root and milk thistle from the original. Most of the recent clinical trial evidence uses this version.

Can I take Iberogast with omeprazole or other PPIs?

There’s no known pharmacological interaction, and it’s often used alongside acid suppression as an add-on for residual dyspeptic symptoms. Tell your doctor you’re taking it, particularly if you’re on anything else processed by the liver. If your PPI isn’t working, it’s worth understanding why reflux medication stops working before layering more products on top.

Does Iberogast work for silent reflux or LPR?

There’s no evidence either way — no LPR trials have been done. Given that LPR damage is driven largely by pepsin rather than acid, and nothing in the formula targets pepsin, there’s no strong mechanistic reason to expect much.

Can peppermint in Iberogast make reflux worse?

It can, in theory. Menthol relaxes the lower oesophageal sphincter, which is why peppermint appears on reflux trigger lists. The amount in 20 drops is small, but if you’re peppermint-sensitive you may notice it. Stop if symptoms worsen in the first week.

Research & References

• Double-blind, randomised, placebo-controlled crossover trial in 18 patients with functional dyspepsia and reflux symptoms, using acid perfusion testing and 24-hour pH-impedance monitoring; the primary reflux questionnaire endpoint was not met, but GERD and regurgitation subscale scores improved and acidic reflux events fell in the pH-confirmed GERD subgroup Oude Nijhuis et al., Journal of Neurogastroenterology and Motility, 2024.
• Meta-analysis pooling raw data from three placebo-controlled trials of STW-5 in functional dyspepsia, finding it significantly more effective than placebo for the most bothersome gastrointestinal symptom, with adverse events comparable to placebo Melzer et al., Alimentary Pharmacology and Therapeutics, 2004.
• Eight-week, double-blind, placebo-controlled multicentre trial in 272 patients with functional dyspepsia, reporting a response rate of 61.2% with STW 5-II versus 45.1% with placebo and no difference in safety parameters Vinson et al., JGH Open, 2024.
• Patient data-based meta-analysis of four randomised controlled trials including 613 patients, showing STW 5-II significantly improved the functional dyspepsia symptom sum score and the key symptoms of fullness, early satiety and epigastric pain at four and eight weeks Andresen et al., Digestion, 2024.
• Review of preclinical and clinical data on STW 5-II, summarising the multiple mechanisms — motility, visceral sensitivity, mucosal inflammation — through which its constituent extracts may act in disorders of gut–brain interaction Annaházi et al., Neurogastroenterology and Motility, 2026.
• Literature review of Chelidonium majus (greater celandine) hepatotoxicity, concluding that multiple cases of herb-induced liver injury have been assessed as probably or highly probably related to exposure, and that the risk-to-benefit ratio of products containing it is negative Pantano et al., European Review for Medical and Pharmacological Sciences, 2017.
• Case report of severe Iberogast-associated hepatotoxicity progressing to acute liver failure and liver transplantation Sáez-González et al., American Journal of Gastroenterology, 2016.
• NIH LiverTox drug record for greater celandine, describing the typical hepatocellular pattern of injury, onset between one and six months of use, and its resemblance to acute viral hepatitis LiverTox, National Institute of Diabetes and Digestive and Kidney Diseases, 2019.