A 2026 randomized controlled trial of 12 active men found that a special starch supplement increased short-chain fatty acids in the gut and protected the intestinal lining during endurance exercise. However, Gram Research analysis shows the supplement did not improve aerobic performance, spare muscle energy, or boost athletic endurance, suggesting that while gut protection occurred, the practical athletic benefits remain unclear.
Researchers tested whether boosting beneficial gut bacteria compounds called short-chain fatty acids could help athletes perform better and preserve muscle energy during exercise. According to Gram Research analysis, while the supplement successfully protected the digestive system during intense workouts, it didn’t improve running speed, save muscle energy stores, or enhance aerobic fitness in healthy young men. The findings suggest that while gut health matters, this particular approach doesn’t deliver the athletic performance boost that animal studies had suggested.
Key Statistics
A 2026 randomized controlled trial published in The Journal of Physiology involving 12 healthy men found that a high-amylose maize starch supplement increased faecal and serum short-chain fatty acids and reduced markers of intestinal barrier damage during endurance exercise.
The same study found no meaningful difference in 5-kilometer time trial performance between the short-chain fatty acid supplement and control, with only 5 seconds separating the conditions (95% confidence interval: -44 to 54 seconds).
Researchers observed a small increase in respiratory exchange ratio of 0.02 units with the short-chain fatty acid supplement during 90 minutes of steady cycling, but this modest change did not translate to improved aerobic performance or muscle glycogen sparing.
The Quick Take
- What they studied: Whether increasing short-chain fatty acids (natural compounds made by gut bacteria) could improve athletic performance and protect the digestive system during endurance exercise.
- Who participated: Twelve healthy, physically active men between ages 18 and 30 years old with good aerobic fitness levels.
- Key finding: The special starch supplement successfully increased short-chain fatty acids in the gut and blood, and it protected the intestinal barrier during exercise. However, it did not improve running performance, save muscle energy, or boost aerobic fitness compared to a regular starch supplement.
- What it means for you: If you’re an athlete looking for a gut health supplement to boost performance, this particular approach may protect your digestive system but won’t give you the athletic edge you’re seeking. Talk to a sports nutritionist about other evidence-based strategies.
The Research Details
This was a randomized controlled trial, which is a gold-standard research design. Twelve active men participated in a crossover study, meaning each person tried both conditions. For 7 days, they ate a controlled diet with either a special high-amylose maize starch (HAMS-A/B) designed to boost short-chain fatty acids in the colon, or a regular low-amylose maize starch (LAMS) as a control. The two conditions were separated by a 2-week break to wash out any lingering effects.
On day 8 of each condition, participants completed a standardized test: 90 minutes of steady cycling at moderate intensity, followed by a 5-kilometer treadmill race against the clock. Researchers measured multiple markers of gut health, energy use, and performance using blood tests, muscle biopsies, urine samples, and indirect calorimetry (a method that measures how much oxygen you use and carbon dioxide you produce).
The study used a double-blind design, meaning neither the participants nor the researchers knew which supplement was which until the study ended. This prevents bias from affecting the results.
This research design is important because it tests whether promising findings from animal studies actually work in real humans. Animal studies had suggested that short-chain fatty acids could be a game-changer for endurance athletes, but human confirmation was missing. By using a crossover design where each person serves as their own control, the researchers could detect even small effects while minimizing individual differences.
This study has several strengths: it used a randomized, double-blind, crossover design (considered high-quality); it measured multiple relevant outcomes; and it was published in a peer-reviewed journal. However, the small sample size of 12 participants limits how much we can generalize the findings to other populations. The study was also relatively short (7 days of supplementation), so longer-term effects remain unknown.
What the Results Show
The special starch supplement successfully did what it was designed to do: it increased short-chain fatty acids in both stool samples and blood. This is important because it confirms the supplement actually delivered the compounds to the right place.
The most significant finding was that markers of intestinal barrier damage and permeability were lower with the HAMS-A/B supplement compared to the control. In simpler terms, the gut lining was better protected during exercise when participants consumed the special starch. This suggests the supplement did protect digestive health.
However, the supplement did not improve aerobic performance. The 5-kilometer time trial results showed no meaningful difference between conditions (only 5 seconds difference, with a confidence interval ranging from -44 to 54 seconds, meaning the result could easily be due to chance). Similarly, the respiratory exchange ratio during the 90-minute cycling session was slightly higher with HAMS-A/B, but this small change (0.02 units) did not translate to better performance or preserved muscle energy.
The researchers measured glucose turnover and muscle protein expression but found no significant differences between conditions. This means the supplement did not spare muscle glycogen (stored carbohydrate energy) or change how muscles used different fuel sources during exercise. The lack of effect on substrate metabolism (how the body uses different energy sources) was surprising given that animal studies had suggested this would happen.
Animal studies had suggested that short-chain fatty acids would act as a glycogen-sparing energy source, meaning muscles could preserve their stored carbohydrate and use the fatty acids instead. This study found that while the supplement did increase short-chain fatty acids and protect gut health, it did not produce the glycogen-sparing or performance-enhancing effects seen in animal models. This highlights a common challenge in nutrition research: findings that work in laboratory animals don’t always translate to humans.
The study included only 12 participants, all healthy young men, so results may not apply to women, older adults, or people with different fitness levels. The intervention lasted only 7 days, which may not be long enough to see performance benefits. The study tested only one type of supplement at one dose, so other formulations or doses might work differently. Finally, the participants were already quite fit (average aerobic capacity of 40 mL/kg/min), so benefits might differ in less trained individuals.
The Bottom Line
Based on this research, we cannot recommend this particular supplement as a performance-enhancing strategy for athletes (low confidence for performance benefits). However, if you have digestive issues during exercise, this supplement may help protect your gut lining (moderate confidence). Always consult a sports nutritionist or doctor before starting any supplement, especially if you have existing digestive conditions.
Athletes concerned about gut health during endurance exercise may find this supplement helpful for digestive protection. However, athletes seeking performance improvements should look elsewhere. People with inflammatory bowel conditions might be interested in the gut-protective effects, but should discuss this with their doctor first.
The study measured effects after just 7 days of supplementation. Any benefits to gut protection appeared quickly, but performance effects (or lack thereof) were evident within this timeframe. Longer-term use might produce different results, but this study provides no evidence for that.
Frequently Asked Questions
Do short-chain fatty acids improve athletic performance?
A 2026 study found that increasing short-chain fatty acids protected gut health during exercise but did not improve running performance, spare muscle energy, or boost aerobic fitness in healthy young men. Animal studies suggested benefits, but human results show no performance advantage.
Can gut bacteria supplements help endurance athletes?
This particular short-chain fatty acid supplement protected the intestinal barrier during exercise but provided no athletic performance benefit in a 12-person trial. Athletes seeking performance gains should explore other evidence-based strategies with their sports nutritionist.
What are short-chain fatty acids and why do they matter?
Short-chain fatty acids are compounds produced by gut bacteria when they digest fiber. They fuel intestinal cells, reduce inflammation, and strengthen the gut barrier. This study confirmed they protect digestive health during intense exercise, though performance benefits remain unproven.
Should I take a short-chain fatty acid supplement before workouts?
If you experience digestive discomfort during exercise, this supplement may help protect your gut lining. However, if your goal is better athletic performance, this study provides no evidence it will help. Consult a sports nutritionist for personalized recommendations.
How long do you need to take this supplement to see results?
This study measured effects after 7 days of supplementation. Gut protection appeared within this timeframe, but performance effects (or lack thereof) were evident quickly. Longer-term effects beyond 7 days remain unknown.
Want to Apply This Research?
- Track digestive comfort during workouts on a scale of 1 to 10 before and after starting any gut-health supplement. Also log energy levels, performance metrics (like time trial results), and any bloating or cramping.
- If using this supplement, take it consistently for at least 7 days before assessing effects. Pair it with consistent exercise and a stable diet to see clear results. Log your perceived digestive comfort and performance metrics in the app to identify patterns.
- Create a weekly check-in to rate digestive health, energy during workouts, and performance outcomes. Compare results across 2-week blocks to identify trends. If you don’t see digestive improvements after 3 to 4 weeks, the supplement may not be right for you.
This research summary is for educational purposes only and should not replace professional medical or sports nutrition advice. The study involved only 12 healthy young men, so results may not apply to all populations. Before starting any supplement, especially if you have digestive conditions, inflammatory bowel disease, or take medications, consult your doctor or a registered sports nutritionist. This supplement has not been evaluated by the FDA for safety or efficacy. Individual results may vary.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.