A 60-day tannin supplement (480 mg daily) reduced IBS-D symptom severity by an average of 70 points and decreased daily bowel movements by 0.84 in a 28-person pilot study, according to Gram Research analysis. The supplement also improved stool consistency, reduced stress and anxiety, and strengthened the gut barrier by lowering zonulin levels. While these results are promising, this small pilot study needs confirmation through larger trials before becoming a standard treatment recommendation.
A new study tested whether a supplement made from tannins—natural compounds found in plants—could help people with diarrhea-predominant irritable bowel syndrome (IBS-D). Twenty-eight adults took 480 mg of this plant extract daily for two months. According to Gram Research analysis, the treatment significantly reduced IBS symptoms, improved bowel regularity, and lowered stress and anxiety levels. The supplement also appeared to strengthen the gut lining and improve the balance of helpful bacteria. While this is a small pilot study, the results suggest that plant-based tannins might offer a natural way to manage IBS-D symptoms without serious side effects.
Key Statistics
A 2026 pilot study of 28 adults with IBS-D found that a tannin-based supplement (480 mg daily) reduced IBS symptom severity by an average of 70 points over 60 days (p < 0.0001), representing a large and highly significant improvement.
According to a 2026 prospective pilot study of 28 IBS-D patients, the tannin supplement decreased daily bowel movements by 0.84 and improved stool consistency by 1.38 points, with both changes statistically significant (p < 0.0001 and p = 0.028, respectively).
A 2026 pilot study found that tannin supplementation reduced perceived stress and somatization scores significantly in 28 IBS-D patients (both p ≤ 0.003), suggesting benefits beyond digestive symptoms.
In a 2026 pilot study of 28 IBS-D patients, zonulin (a marker of intestinal barrier dysfunction) dropped significantly with tannin supplementation (p < 0.0001), while beneficial butyrate increased (p = 0.001), indicating improved gut health.
The Quick Take
- What they studied: Whether a supplement containing tannins (natural plant compounds) could reduce symptoms in people with IBS-D, a condition causing chronic diarrhea and stomach problems.
- Who participated: 28 adults diagnosed with diarrhea-predominant IBS who took a daily tannin supplement (480 mg) for 60 days. This was a small pilot study to test if the approach was safe and showed promise.
- Key finding: IBS symptom severity dropped by an average of 70 points on a standard scale (p < 0.0001), stool consistency improved significantly, and bowel movements decreased by about one per day. Stress and anxiety scores also improved notably.
- What it means for you: If you have IBS-D, this suggests a natural plant-based supplement might help reduce your symptoms within two months. However, this is a small pilot study, so larger research is needed before making it a standard recommendation. Talk to your doctor before starting any new supplement.
The Research Details
This was a prospective pilot study, which means researchers followed the same 28 people over time to see what happened when they took the supplement. Everyone in the study had IBS-D, and they all took the same tannin-based supplement for 60 days. Researchers measured multiple things: how severe their IBS symptoms were, their bowel habits, stress levels, anxiety symptoms, and several biological markers in their blood and stool that indicate gut health.
The researchers used a statistical method called linear mixed models to analyze how things changed from the beginning to the end of the study. This approach accounts for individual differences and helps identify real changes caused by the treatment rather than random variation.
Because this was a pilot study with no control group (a group that didn’t take the supplement), we can’t be completely certain the supplement caused all the improvements. However, the large improvements and consistent changes across multiple measures suggest the supplement had a real effect.
Pilot studies are important because they test whether a new treatment is safe and shows enough promise to justify larger, more expensive studies. This research matters because IBS-D affects millions of people and current treatments don’t work well for everyone. By identifying a natural approach that targets multiple problems (gut barrier, bacteria balance, and stress), researchers can design better studies to confirm whether this really works.
Strengths: The study measured multiple outcomes (symptoms, stress, and biological markers), used validated assessment tools, had no dropouts, and reported no adverse events. The statistical improvements were large and highly significant. Limitations: The small sample size (28 people) means results might not apply to everyone. There was no control group for comparison, so we can’t rule out placebo effect. The study lasted only 60 days, so we don’t know if benefits last longer. Larger randomized controlled trials are needed to confirm these findings.
What the Results Show
The tannin supplement produced substantial improvements in IBS-D symptoms. On the standard IBS Severity Scoring System, symptoms decreased by an average of 70 points (95% confidence interval: 34-107), which is a large and statistically significant change (p < 0.0001). This means researchers are very confident this improvement was real and not due to chance.
Bowel function improved notably: stool consistency improved by 1.38 points on the measurement scale (p < 0.0001), and the number of bowel movements per day decreased by 0.84 (p = 0.028). These changes mean people had fewer, more normal stools—exactly what someone with IBS-D would want.
Psychological symptoms also improved significantly. Both somatization (the tendency to experience physical symptoms related to stress) and perceived stress scores declined meaningfully (both p ≤ 0.003). This suggests the supplement helped with the stress and anxiety that often accompany IBS-D.
Biological markers showed changes consistent with improved gut health. Zonulin, a protein that indicates leaky gut (when the intestinal barrier becomes too permeable), dropped significantly (p < 0.0001). This suggests the supplement strengthened the gut barrier. Butyrate, a beneficial short-chain fatty acid produced by healthy gut bacteria, increased (p = 0.001). Propionate, another short-chain fatty acid, decreased (p = 0.017). These changes indicate the supplement improved the balance and function of gut bacteria. Additionally, all three participants who tested positive for small intestinal bacterial overgrowth (SIBO) at the start—detected by hydrogen breath test—tested negative after 60 days, suggesting the supplement may help reduce problematic bacterial overgrowth.
This research builds on earlier studies showing that tannins have anti-inflammatory and barrier-protective properties. Previous research suggested tannins could help with diarrhea and gut inflammation, but few studies had tested this in IBS-D specifically or measured the gut-brain connection. This pilot study is novel because it examined multiple pathways simultaneously—barrier function, bacterial balance, and psychological stress—which aligns with current understanding that IBS-D involves dysregulation of the gut-brain axis. The results are encouraging compared to limited nutritional options currently available for IBS-D management.
This pilot study has important limitations. With only 28 participants and no control group, we can’t be certain the supplement caused all improvements—some could be due to placebo effect or natural variation. The study lasted only 60 days, so we don’t know if benefits persist longer or if people maintain improvements after stopping the supplement. The sample was relatively small and may not represent all people with IBS-D, especially different ages, ethnicities, or disease severity levels. The study didn’t track diet or lifestyle changes that might have contributed to improvements. Finally, because this was published in 2026, longer-term follow-up data from larger trials may now be available.
The Bottom Line
Based on this pilot study, a tannin-based supplement (480 mg daily) appears safe and may help reduce IBS-D symptoms within 60 days. However, confidence is moderate because this is a small pilot study. Before starting any supplement, consult your doctor, especially if you take medications or have other health conditions. This research suggests tannins are worth investigating further, but it’s not yet strong enough evidence to recommend as a standard treatment. Larger studies are needed to confirm these findings.
People with IBS-D who haven’t found relief with current treatments should find this interesting and worth discussing with their doctor. Those interested in natural approaches to digestive health may also benefit. However, people with severe IBS-D, those taking medications that interact with tannins, or pregnant/nursing women should consult healthcare providers before trying this supplement. This research is preliminary, so it shouldn’t replace medical advice or proven treatments.
Based on this study, most improvements appeared within 60 days. Bowel consistency and frequency improved relatively quickly, while stress and anxiety improvements also occurred within this timeframe. However, individual responses vary. Some people might see benefits sooner, while others might need the full 60 days. It’s unclear from this study whether benefits continue beyond 60 days or if they persist after stopping the supplement.
Frequently Asked Questions
Can tannin supplements help with IBS diarrhea?
A 2026 pilot study of 28 people found tannin supplements (480 mg daily) significantly reduced IBS-D symptoms by 70 points and decreased bowel movements by about one per day within 60 days. However, this small study needs larger confirmation before recommending it as standard treatment.
How long does it take for tannin supplements to work on IBS symptoms?
In the 2026 pilot study, improvements in bowel consistency, frequency, and stress appeared within the 60-day study period. Individual responses vary, so some people might see benefits sooner while others need the full 60 days. Longer-term effects beyond 60 days are unknown.
What are tannins and where do they come from?
Tannins are natural compounds found in plants like pomegranate, green tea, and grape seeds. They have anti-inflammatory and barrier-protective properties. The 2026 study used a tannin-based supplement containing 480 mg daily, but the exact plant sources weren’t detailed in the abstract.
Does the tannin supplement improve gut bacteria in IBS?
Yes, the 2026 pilot study found that tannin supplementation increased butyrate (a beneficial short-chain fatty acid) and improved bacterial balance markers. All three participants with small intestinal bacterial overgrowth at baseline tested negative after 60 days.
Are there any side effects from tannin supplements for IBS?
The 2026 pilot study reported no adverse events in 28 participants taking 480 mg daily for 60 days. However, this is a small study, so rare side effects might not have been detected. Consult your doctor before starting any supplement, especially if you take medications.
Want to Apply This Research?
- Track daily bowel movements (number and consistency on a 1-7 scale), stress level (1-10 scale), and overall IBS symptom severity daily. Measure these for one week before starting the supplement, then continue throughout the 60-day period to see your personal response.
- Start taking 480 mg of tannin-based supplement daily (as used in the study) while logging your symptoms each evening. Pair this with consistent meal times and adequate hydration. Use the app to set daily reminders for supplement intake and symptom logging.
- Create a dashboard showing your 60-day trend for bowel movements, stool consistency, and stress levels. Compare your week-one baseline to weeks 4, 8, and 12. If you see improvement by week 8, continue for the full 60 days. Share your tracked data with your doctor to inform treatment decisions.
This article summarizes a pilot research study and is for educational purposes only. It is not medical advice. IBS-D is a complex condition requiring individualized treatment. Before starting any supplement, including tannin-based products, consult with your healthcare provider, especially if you have other health conditions, take medications, are pregnant, or are nursing. This pilot study involved only 28 participants and lacks a control group, so larger studies are needed to confirm these findings. Do not replace prescribed IBS treatments with supplements without medical guidance. Results from this study may not apply to all individuals.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.