Guide

Does Chinese herbal medicine work for IBS? The Cochrane review, the JAMA trial and what came after

Chinese herbal medicine is among the most-tested complementary treatments for irritable bowel syndrome, and the trials do not agree with one another. This guide covers the 1998 JAMA trial, the Cochrane review of 75 trials, the meta-analyses and placebo trials since, berberine in IBS-D, the problem that individualized prescribing poses for trial design, and how the evidence sits next to peppermint oil and psyllium. The formulas are taken one by one in Classic Chinese digestive formulas: what the trials show. For background see What is traditional Chinese medicine? and the glossary of key concepts for the gut; the TCM section lists the whole series.

The JAMA trial of 1998

A Sydney group randomized 116 people who met the Rome criteria for IBS, recruited through two teaching hospitals and five gastroenterology practices, to three arms: a standard Chinese herbal formula (43 people), a formula written for each person by a herbalist (38), or placebo (35). Everyone took five capsules three times a day for 16 weeks, and patients, gastroenterologists and herbalists were all blinded (PMID 9820260).

Compared with placebo, the two active arms improved on the bowel symptom scale as rated by patients (p = 0.03) and by gastroenterologists (p = 0.001), and on global improvement as rated by patients (p = 0.007) and gastroenterologists (p = 0.002). The individualized formulas were no more effective than the standard one. Fourteen weeks after treatment ended, only the individualized group had kept its improvement. As tabulated in later reviews, patient-rated global improvement was 29 of 43 on the standard formula, 18 of 38 on the individualized formulas and 11 of 35 on placebo, the placebo arm having been split across the two comparisons as 6 of 18 and 5 of 17 (PMID 27547226). The Cochrane review re-analyzed the trial with 99% confidence intervals and rated it good quality: the standard formula’s relative risk for patient-rated global improvement was 2.15 (99% CI 1.07 to 4.32) and the individualized formulas’ was 1.51 (99% CI 0.69 to 3.29); at the 14-week follow-up the standard formula’s effect on the bowel symptom scale was no longer significant. Two people left the trial because of discomfort, one with upper abdominal discomfort and one with headaches.

The Cochrane review of 2006

Liu and colleagues searched through 2004, and Chinese journals through 2003, with no language limit. They found 75 randomized trials with 7,957 participants testing 71 different herbal medicines (PMID 16437473). Three double-blind, placebo-controlled trials were of high methodological quality, and the quality of the rest was generally low. Against placebo, a standard Chinese formula, individualized Chinese herbal medicine, the German combination STW 5 and its variant STW 5-II, the Tibetan formula Padma Lax, Tong Xie Yao Fang and an Ayurvedic preparation improved global symptoms. Against conventional treatment in 65 trials of 51 herbal medicines, 22 showed a statistically significant benefit and 29 did not differ. The authors concluded that some herbal medicines may improve IBS symptoms, that positive findings from less rigorous trials need caution because of inadequate methods and small samples, and that some deserve high-quality trials. Only 18 of the 75 trials (24%) reported adverse events, and the review did not draw a conclusion on safety.

Meta-analyses and trials since

The Tong Xie Yao Fang placebo trials split. In 160 adults with IBS-D, adequate relief over four weeks was 57.5% on the granules against 37.5% on placebo (PMID 29856472). In 96 adults over eight weeks, the response was 79.2% against 70.8% (ratio 1.12, 95% CI 0.89 to 1.41), and the authors suggested symptoms fell in both arms regardless of treatment (PMID 39870499). The formula contains atractylodes, white peony, orange peel and saposhnikovia. A separate Australian trial tested a standardized seven-ingredient extract in 125 people with constipation-predominant IBS across 13 centers: for 8 weeks, adequate relief was greater on the extract (p = 0.010, per-protocol, 50 against 58 people) and so was stool consistency, but abdominal pain did not differ (p = 0.692; PMID 26133902).

Berberine in IBS-D

Berberine is an isolated alkaloid from plants such as coptis, not a formula, and its IBS trial is placebo-controlled. In Shanghai, 196 people with IBS-D were recruited and 132 randomized to berberine hydrochloride, 400 mg a day delivered twice daily, or placebo for 8 weeks, followed by a 4-week washout. Berberine reduced the frequency of diarrhea (p = 0.032), abdominal pain (p < 0.01) and urgent need to defecate (p < 0.01) more than placebo, and symptom score, anxiety, depression and quality of life moved in the same direction at p < 0.05 (PMID 26400188). It is one single-center trial. The berberine page covers the wider trial record.

The problem of individualized prescribing

In traditional practice the herbalist chooses and adjusts herbs for the pattern found on examination, and that is hard to test. A trial can give everyone one fixed formula, which tests the formula but not the tailoring, or let a herbalist write each prescription, which tests the tailoring but cannot be repeated exactly. The JAMA trial did both and found no extra benefit from individualizing at the end of treatment, though the individualized arm held its gains at the 14-week follow-up. Whether practitioners agree on the pattern is a separate question. In a University of Maryland study, three licensed acupuncturists examined the same 40 people with rheumatoid arthritis and agreed on the diagnosis 31.7% of the time, while 91.7% of their prescriptions matched the textbook for the diagnosis each had chosen (PMID 15992224); we found no equivalent study in IBS.

Pattern labels appear in IBS-D trials too. Zhu et al. grouped formulas by the pattern they target: those described as soothing the liver and invigorating the spleen gave a relative risk of 1.42 (95% CI 1.08 to 1.86) and those described as warming the kidney and invigorating the spleen gave 2.06 (95% CI 1.71 to 2.47). One trial had added heat-clearing herbs the authors judged unsuited to the syndrome, and leaving it out lowered heterogeneity from 59% to 0% with a ratio of 1.82 (95% CI 1.60 to 2.08).

How this compares with peppermint oil and psyllium

The three bodies of evidence differ in kind. Peppermint oil and psyllium are single ingredients tested at set doses, and the American College of Gastroenterology 2021 guideline grades peppermint oil as a weak, low-certainty option for overall symptoms (PMID 33315591). The Chinese trials mostly test multi-herb formulas: the Cochrane review counted 71 different herbal medicines, and a Tong Xie Yao Fang review found the herb ratios varied between trials with no justification given. Most of the IBS-D placebo trials in the pooled analysis were conducted in China and published in Chinese.

Safety in the IBS trials

Adverse events were reported unevenly. A meta-analysis of seven placebo-controlled trials with 1,512 participants found treatment-related events more common on the herbal arm (RR 1.51, 95% CI 1.14 to 2.00), mostly mild: nausea, constipation, diarrhea, bloating, with some rash and raised liver enzymes (PMID 34385918). Against pinaverium the rates did not differ, and the IBS-D placebo meta-analysis found no difference (PMID 27547226). An earlier review put the incidence at 2.97% (PMID 18200670), and the Cochrane review found adverse events were reported in fewer than a quarter of trials. Liver injury has been reported with some Chinese formulas outside IBS trials, including bupleurum-based Xiao Chai Hu Tang (PMID 24844799). Are Chinese herbal supplements safe? goes through the case reports, contaminants and herb-specific risks, and TCM in the United States and Europe covers how the products are regulated.

The catalog entries behind this guide

Common questions

Sources

• Bensoussan A, Talley NJ, Hing M, Menzies R, Guo A, Ngu M. “Treatment of irritable bowel syndrome with Chinese herbal medicine: a randomized controlled trial.” JAMA, 1998;280(18):1585–1589. pubmed.ncbi.nlm.nih.gov/9820260
• Liu JP, Yang M, Liu YX, Wei M, Grimsgaard S. “Herbal medicines for treatment of irritable bowel syndrome.” Cochrane Database of Systematic Reviews, 2006;(1):CD004116. Trial data for Bensoussan 1998 and adverse-event reporting from the full text. pubmed.ncbi.nlm.nih.gov/16437473; pmc.ncbi.nlm.nih.gov/articles/PMC12522099
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