A few digestive supplements have real trials, and most run on tradition

Key takeaways

• In 1988, the FDA found no adequate evidence that betaine hydrochloride treats low stomach acid, so it can’t be sold over the counter as a stomach-acid drug without approval; it’s still sold as a supplement⁸⁹.
• Artichoke leaf extract beat a placebo for chronic indigestion in a six-week trial of 247 adults, one of the better-tested options in the aisle⁴.
• The herbal formula STW 5, sold as Iberogast, eased indigestion in trials, but its German label added liver warnings in 2018 after reports of severe liver injury, including a death²³.
• We found little or no solid human evidence that DGL licorice, slippery elm, activated charcoal or digestive bitters relieve gut symptoms¹⁰¹².
• Activated charcoal can bind medicines, including birth control pills, and licorice that still contains glycyrrhizin can endanger people with high blood pressure or heart disease¹⁰¹².

Iberogast, a liquid extract of nine herbs, has something most digestive remedies lack: randomized trials showing it eases indigestion²³.

It also contains greater celandine, a plant linked to liver damage. In 2008, Germany’s drug regulator pulled approval for celandine products above a set daily dose after 48 case reports. It told lower-dose products, including Iberogast, to add liver warnings².

Iberogast’s leaflet didn’t carry those warnings until September 2018. Bayer, which had marketed the product since 2013, added them after new reports of severe liver injury, including one death, and as the regulator moved to force the change².

Writing in the bulletin of Germany’s medical drug commission, Hamburg physician Ulrich Rosien concluded that the formula could no longer be recommended for any use while it contained celandine. He urged Bayer to take the plant out².

That one product tells the story of the whole digestive supplement aisle. Some products have real trials. Some carry real risks. A few have both, and many have neither, only tradition and marketing.

Below, we look at how popular ones measure up on our four-level evidence scale.

A supplement can reach the shelf without proof it works

In the United States, a company doesn’t have to prove a dietary supplement is safe or effective before selling it, as NIH’s complementary health center points out¹. Much about the safety of herbal products is still unknown¹.

So the judging falls to you. Three questions help.

What exactly was tested? A trial of one artichoke extract at one dose doesn’t vouch for a different brand at a different dose. Our articles on Supplement Facts panels and on batch testing explain how to compare.

For what problem? Most of the better trials here involve functional dyspepsia, chronic indigestion with no visible cause. NIDDK, the federal digestive disease institute, says most chronic indigestion falls into this group, which it describes as a problem in the way the gut and brain communicate¹³.

Compared with what? Indigestion trials can have very high placebo responses, up to about 60% in some trials of STW 5². A product has to beat that to count.

Artichoke leaf and two herbal blends have the best indigestion trials

Artichoke leaf extract. In a six-week trial published in 2003, 247 adults with functional dyspepsia took an artichoke leaf extract or a placebo, a look-alike dummy pill. The extract dose totaled 1,920 mg a day, split into three doses⁴.

Symptoms improved in both groups, but more with the extract: 8.3 points versus 6.7 on the trial’s symptom score. Quality of life on a dyspepsia questionnaire improved more, too⁴.

A 2015 Italian trial tested a capsule combining artichoke leaf and ginger extracts in 126 adults for four weeks. By the end, 63% of the supplement group had a marked drop in symptoms, versus 25% on placebo⁵.

That trial’s fine print deserves a look. The supplier, Indena, provided the capsules and placebos free, and three authors listed its research unit as their workplace, yet the paper declared no conflicts of interest⁵. That doesn’t make the result wrong. It’s the kind of detail you’d want to know about a drug trial, too.

STW 5 (Iberogast). A 2004 analysis pooled three placebo-controlled trials with 273 people. STW 5 eased each person’s most bothersome symptom more than placebo did, and side effects were similar³. The analysts found trials partly by asking the manufacturer³.

The German drug bulletin flagged two weaknesses: placebo responses up to about 60%, and placebos that weren’t regularly matched to the formula’s taste². When a remedy has a distinct taste, an unmatched placebo can tip people off about which group they’re in.

Peppermint and caraway oil. NCCIH says certain products that pair peppermint oil with caraway oil have shown promise for indigestion in some studies. Peppermint oil alone hasn’t been shown to help indigestion and may make it worse⁶.

Our rating for all three is Promising but early. The trials are real and placebo-controlled, but they’re few and short, and some are tied to the companies that sell the products.

A tested herbal formula still needed a liver warning

Iberogast shows that trial evidence and safety are separate questions.

After the 2018 change, the German label told users to have liver enzymes checked if they took it longer than four weeks. It warned against use with current or past liver disease or with other drugs that can harm the liver. It said to stop at the first sign of liver trouble and not to use it during pregnancy or breastfeeding².

Europe’s medicines agency had already reached a negative view of the benefits and risks of celandine products around 2010 to 2011².

Check the ingredients of any herbal digestive blend for celandine, listed as Chelidonium majus. We couldn’t confirm the current U.S. formula, so check the bottle you have.

If you have liver disease or take medicines that can strain the liver, ask your clinician before using any herbal blend. Yellowing of the eyes or skin is a reason to seek care right away, NIDDK says¹³.

Peppermint oil and ginger help with narrow jobs, and can cause heartburn

Peppermint oil has backing from a major U.S. guideline. The American College of Gastroenterology’s 2021 guideline on irritable bowel syndrome (IBS) recommended peppermint oil for overall symptom relief⁶.

NCCIH adds that a 2022 review of 10 studies found peppermint oil beat a placebo for overall IBS symptoms and belly pain, though it caused more side effects, mostly mild⁶. But our article on reading research abstracts walks through a 2020 trial that missed its main goal. With mixed results like these, we rate it Promising but early for IBS.

Ginger has a narrower record. Research suggests it may ease nausea and vomiting in pregnancy, mostly in studies of supplements. It’s uncertain for nausea after chemotherapy or surgery, and most studies haven’t found it helpful for motion sickness⁷. Our upcoming ginger article goes deeper.

The twist: both can cause heartburn. Oral peppermint oil can bring on heartburn, nausea and belly pain, and enteric-coated capsules, built to open past the stomach, may reduce that⁶. Ginger can cause heartburn, belly discomfort and diarrhea⁷.

So if reflux is your main complaint, these two may not be your best picks. Keep peppermint oil away from the faces of babies and young children, and ask before using ginger supplements in pregnancy⁶⁷.

The low-stomach-acid theory and betaine HCl

A popular idea in natural health holds that many digestive complaints, including heartburn, bloating and the feeling that food sits in the stomach, come from too little stomach acid rather than too much. The suggested fix is betaine hydrochloride, or betaine HCl, a supplement that adds acid.

Part of the theory rests on real science. Low stomach acid exists, and acid-reducing drugs cause it on purpose. In a small 2013 study, the acid blocker rabeprazole pushed six volunteers’ stomach pH up to about 5.2, far less acidic than usual⁸.

Betaine HCl reversed that fast. A 1,500 mg dose dropped stomach pH below 3 within about 6 minutes on average, but the effect faded after about 73 minutes⁸. No significant side effects showed up.

The drug company Genentech funded the study through a grant, with NIH support. The researchers’ interest was practical: whether betaine could help people on acid reducers absorb certain medicines⁸.

What’s missing is evidence that betaine HCl relieves digestive symptoms. The authors noted that its effect on stomach acid hadn’t been thoroughly studied in people⁸.

The FDA weighed in decades ago. In a 1988 rule, it found a lack of adequate data showing that betaine HCl, glutamic acid HCl, diluted hydrochloric acid or pepsin treat low stomach acid. The rule also called those conditions asymptomatic, meaning they don’t cause symptoms on their own⁹.

Since then, any over-the-counter product sold as a stomach acidifier counts as a new drug that needs FDA approval⁹. Betaine HCl is still sold, as a dietary supplement⁸. Our article on supplement claims explains why such labels say “supports digestion” rather than “treats.”

Rating: Not enough evidence. If you take an acid reducer your clinician prescribed, don’t add a product designed to do the opposite without asking. Heartburn that keeps coming back is a reason to see a clinician, not to self-treat for years. Our reflux article covers what works.

Soothers and binders: DGL, slippery elm, aloe, charcoal and bitters

DGL licorice. Licorice root is promoted for digestive support¹⁰. Its compound glycyrrhizin is the problem. In large amounts or with long use, it has been linked to irregular heartbeat and cardiac arrest, and even small amounts have caused severe effects in people with a salty diet, high blood pressure, or heart or kidney disease¹⁰.

DGL, short for deglycyrrhizinated licorice, has the glycyrrhizin removed¹⁰. Whether licorice-only products help digestive symptoms is unclear, NCCIH says¹⁰. Rating: Not enough evidence.

Slippery elm. This tree bark is sold as a soothing remedy for the throat and stomach. We found no controlled trials of slippery elm alone for heartburn or indigestion, so we can’t say whether it helps. Rating: Not enough evidence.

Aloe. In 2002, an FDA ruling forced aloe latex out of over-the-counter laxatives¹¹. A whole-leaf aloe extract that hadn’t been decolorized has been linked to gut cancers in rats and mice, and the International Agency for Research on Cancer classified it as a possible human carcinogen¹¹.

Oral aloe leaf extracts have also been tied to cases of acute hepatitis, after anywhere from three weeks to five years of use¹¹. For IBS, there isn’t enough reliable information¹¹. Rating for laxative use: Evidence says no, or unsafe. Our article on digestive cleanses covers stimulant laxatives.

Activated charcoal. Charcoal capsules are sold to soak up gas. Jacqueline Wolf, a gastroenterologist at Beth Israel Deaconess Medical Center, told Medscape in 2019 that the research on gas is contradictory. Most of it dates to the 1980s, and only two studies saw a benefit¹². Rating: Not enough evidence.

Its binding power is the bigger issue. The list of medicines charcoal can grab includes birth control pills, diabetes drugs, antidepressants, seizure and heart-rhythm medicines, and common painkillers¹². Hospitals give 50 grams for poisoning, and in one study that dose cut a drug’s absorption by an average of 47% if taken within half an hour¹².

A typical supplement holds about 500 mg, a hundredth of that. Still, Christopher Holstege, who directs a poison center at the University of Virginia, said the risk is greatest when charcoal and a medicine go down around the same time¹².

Digestive bitters. These are bitter-tasting plant extracts that sellers promote for digestion. We found no controlled trials of bitters products for digestive symptoms, so we can’t say whether they help. Rating: Not enough evidence.

The digestive supplement scorecard

Product	Used for	Best evidence	Rating	Safety notes	Interactions
Artichoke leaf extract	Chronic indigestion	Six-week trial, 247 adults4	Promising but early	Trials lasted six weeks or less45	Ask a pharmacist if you take prescriptions14
Artichoke plus ginger	Chronic indigestion	Four-week trial, 126 adults5	Promising but early	Supplier-linked trial; ginger can cause heartburn57	Ask a pharmacist if you take prescriptions14
STW 5 (Iberogast)	Chronic indigestion	Three pooled trials, 273 people3	Promising but early	Liver warnings over celandine2	Avoid with liver-harming drugs; not in pregnancy2
Peppermint plus caraway oil	Chronic indigestion	Some studies favor specific products6	Promising but early	Heartburn possible6	Ask first if you take medicines6
Peppermint oil capsules	IBS	10-study review and 2021 ACG guideline favor it6	Promising but early	Heartburn; keep off babies’ faces6	Ask first if you take medicines6
Ginger	Pregnancy nausea	Several studies, mostly supplements7	Promising but early	Heartburn, diarrhea7	Ask first in pregnancy7
Betaine HCl	Low stomach acid, heartburn	Six-person acid study; no symptom trials8	Not enough evidence	FDA found evidence inadequate in 19889	Counteracts prescribed acid reducers8
DGL licorice	Heartburn, indigestion	Benefit unclear10	Not enough evidence	Possibly safe for four months10	Ask if you take medicines10
Licorice with glycyrrhizin	Digestive support	Benefit unclear; harms documented10	Evidence says no, or unsafe for people with heart, kidney or blood pressure problems	Irregular heartbeat, cardiac arrest10	Corticosteroids10
Slippery elm	Soothing, heartburn	No controlled trials found	Not enough evidence	No safety data reviewed	Ask a pharmacist14
Aloe latex or whole-leaf extract	Constipation	FDA pulled it from OTC laxatives in 2002 for lack of safety data11	Evidence says no, or unsafe	Hepatitis cases; cancer in rodents11	Digoxin11
Activated charcoal	Gas	Contradictory 1980s studies12	Not enough evidence	Vomiting, rare blockage12	Binds many medicines12
Digestive bitters	Appetite, digestion	No controlled trials found	Not enough evidence	No safety data reviewed	Ask a pharmacist14
Apple cider vinegar	Heartburn, digestion	See our reflux article	Not enough evidence	Acidic	Ask a pharmacist14

Three other shelves have their own articles. Our article on digestive enzymes covers lactase, bean enzymes and enzyme blends. Our articles on leaky gut cover L-glutamine, and our upcoming probiotics article matches strains to goals.

How to try a digestive supplement fairly

If you decide to try one, give it a real test rather than a hopeful guess.

1. Rule out warning signs first. NIDDK says to seek care right away if indigestion comes with chest, jaw, neck or arm pain, trouble swallowing, frequent or bloody vomiting, severe constant belly pain, long-lasting bloating, shortness of breath, weight loss without trying, yellow eyes or skin, or black, tarry stools¹³.
2. Match the trial. Choose the type of product and the dose that was studied, not just the plant name on the front⁴⁵.
3. Change one thing at a time. Try one product for about the length of the trials, four to six weeks, and keep a simple symptom log⁴⁵.
4. Check interactions. Ask a pharmacist, especially if you take warfarin, digoxin or cancer drugs, where small changes matter¹⁴. Most known herb-drug interactions come from lab and animal work, so a missing warning isn’t proof of safety¹⁴.
5. Check quality. Our articles on Supplement Facts panels and on contamination show what to look for on a label.
6. Stop and report problems. Report side effects to the FDA’s Safety Reporting Portal at safetyreporting.hhs.gov.

Tradition earned many of these plants a place on the shelf. Testing shows which traditions hold up, and for which problems. Respecting both means giving a promising herb a fair trial, and walking away from one that doesn’t deliver or that carries a warning.

Questions readers ask

The bottom line

The digestive supplement aisle is not all hope and no proof. Artichoke leaf extract and STW 5 have placebo-controlled trials for chronic indigestion, peppermint oil has a guideline nod for IBS, and ginger may ease nausea in pregnancy. The indigestion evidence rests on a handful of short studies, and STW 5 carries a liver warning because of celandine.

Betaine HCl, DGL, slippery elm, charcoal and bitters have little evidence for gut symptoms, and aloe latex and high-glycyrrhizin licorice carry documented risks. Choose the tested product and dose, try one at a time, check interactions with a pharmacist, and see a clinician for symptoms that persist or come with warning signs.

Related reading

• Your body makes digestive enzymes to spare, and pills help when it can’t
• The supplement facts panel and the blend that hides your dose
• What gets into supplements that isn’t on the label
• How to read a study abstract in two minutes, including one that spins a failed trial
• Reflux responds to habits, and acid pills are safer than headlines say

Sources

1. National Center for Complementary and Integrative Health. “Safe Use of Complementary Health Products and Practices.” NIH, accessed October 2026. nccih.nih.gov
2. Rosien U. “Iberogast verursacht potenziell lebensbedrohliche Leberschäden” (Iberogast causes potentially life-threatening liver damage). Arzneiverordnung in der Praxis (Drug Commission of the German Medical Association), 2019;46(1-2), published online October 17, 2018. akdae.de
3. Melzer J, et al. “Meta-Analysis: Phytotherapy of Functional Dyspepsia With the Herbal Drug Preparation STW 5 (Iberogast).” Alimentary Pharmacology & Therapeutics, 2004 (Epistemonikos record). epistemonikos.org
4. Holtmann G, Adam B, Haag S, Collet W, Grünewald E, Windeck T. “Efficacy of Artichoke Leaf Extract in the Treatment of Patients With Functional Dyspepsia: A Six-Week Placebo-Controlled, Double-Blind, Multicentre Trial.” Alimentary Pharmacology & Therapeutics, 2003;18(11-12):1099-1105 (University of Adelaide repository). pubmed.ncbi.nlm.nih.gov
5. Giacosa A, et al. “The Effect of Ginger and Artichoke Extract Supplementation on Functional Dyspepsia: A Randomised, Double-Blind, and Placebo-Controlled Clinical Trial.” Evidence-Based Complementary and Alternative Medicine, 2015:915087. pmc.ncbi.nlm.nih.gov
6. National Center for Complementary and Integrative Health. “Peppermint Oil.” NIH, last updated May 2025. nccih.nih.gov
7. National Center for Complementary and Integrative Health. “Ginger.” NIH, last updated February 2025. nccih.nih.gov
8. Yago MAR, Frymoyer AR, Smelick GS, et al. “Gastric Re-acidification With Betaine HCl in Healthy Volunteers With Rabeprazole-Induced Hypochlorhydria.” Molecular Pharmaceutics, 2013;10(11):4032-4037 (University of California eScholarship). escholarship.org
9. U.S. Food and Drug Administration. 21 CFR 310.540, “Drug Products Containing Active Ingredients Offered Over-the-Counter (OTC) for Use as Stomach Acidifiers.” 53 FR 31271, August 17, 1988 (text via Federal-Regs). federal-regs.com
10. National Center for Complementary and Integrative Health. “Licorice Root.” NIH, last updated April 2025. nccih.nih.gov
11. National Center for Complementary and Integrative Health. “Aloe Vera.” NIH, last updated February 2025. nccih.nih.gov
12. Medscape Gastroenterology. “What Doctors Need to Know About the Activated Charcoal Trend.” July 17, 2019 (republished by University of Colorado Anschutz Medical Campus). news.cuanschutz.edu
13. National Institute of Diabetes and Digestive and Kidney Diseases. “Symptoms & Causes of Indigestion.” NIDDK, last reviewed March 2025. niddk.nih.gov
14. National Center for Complementary and Integrative Health. “Herb-Drug Interactions.” NCCIH Clinical Digest, December 2024. nccih.nih.gov