New Consensus on Gut Training for Endurance Athletes
The 2025 Joint Position Statement on exercise-induced gastrointestinal syndrome (EIGS) identifies gut training and specific carbohydrate fueling strategies as Grade I evidence for endurance performance, while dismissing probiotics and chronic low-carb diets.
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A new joint position statement from Sports Dietitians Australia (SDA) and the Ultra Sports Science Foundation (USSF) offers clarity on effective gut training for endurance athletes. The 2025 statement, Costa et al., grades interventions based on evidence, highlighting what works and what doesn't for preventing exercise-induced gastrointestinal syndrome (EIGS) and optimizing performance [Source](https://nutritional-revolution.com/gut-training-for-endurance-athletes/?srsltid=AfmBOoq8P-BFFLJT1PleQ4MHeMP-Kt0T8R6aGqc xKoy-cdUG9ZRIL4Xp).
Gut training involves progressively increasing carbohydrate intake during exercise over several weeks. This practice is now considered Grade I evidence, representing the strongest level of support for its effectiveness.
What is Gut Training?
Gut training is a systematic, multi-week protocol where athletes gradually increase the amount of carbohydrates consumed during exercise. This isn't a quick fix for race week but a structured regimen parallel to other physical training. It aims to adapt the gastrointestinal tract to handle higher nutrient loads during competition.
The minimum effective dose for measurable adaptation is two weeks, but eight to twelve weeks is often necessary for optimal race-day preparation. For events longer than three hours, a minimum of ten weeks of gut training is recommended, while six to eight weeks may suffice for two-to-three-hour races.
How the Gut Adapts to Training
The effectiveness of gut training stems from specific physiological adaptations. The intestine uses transporters like SGLT1 (for glucose and maltodextrin) and GLUT5 (for fructose) to move carbohydrates into the bloodstream. SGLT1 saturates at approximately 60 grams of glucose per hour, leading to gastrointestinal issues if exceeded with glucose-only products.
By combining glucose and fructose, which use different pathways, athletes can absorb more than 90 grams per hour, potentially reaching 120 grams per hour. Repeated exposure to high-carbohydrate fueling upregulates the density and activity of SGLT1 in the intestine, improving the body's ability to process carbohydrates [Source](https://nutritional-revolution.com/gut-training-for-endurance-athletes/?srsltid=AfmBOoq8P-BFFLJT1PleQ4MHeMP-Kt0T8R6aGqc xKoy-cdUG9ZRIL4Xp).
Evidence-Based Interventions
The 2025 Costa et al. position paper graded interventions for EIGS prevention and performance enhancement. Three key strategies received Grade I evidence:
- Carbohydrate intake during exercise (60–90 g/hr): This practice increases blood flow to the gut, mitigating splanchnic ischemia that contributes to EIGS. Studies show that 90 g/hr can significantly reduce gut barrier injury markers.
- Two-week gut training: This practice can reduce carbohydrate malabsorption and gut discomfort by nearly 50% after just two weeks of structured fueling between 30–90 g/hr.
- Low-FODMAP eating 24–48 hours pre-race: This dietary adjustment can reduce gastrointestinal symptom severity by about 50%.
Conversely, several popular interventions received a
Key takeaways
- 01The 2025 SDA/USSF Joint Position Statement identifies gut training as Grade I evidence for endurance athletes.
- 02Deliberate, progressive carbohydrate intake during training over 8-12 weeks enhances the gut's ability to absorb fuel.
- 03Combining glucose and fructose allows for higher carbohydrate absorption rates (up to 120g/hr) by utilizing separate transporters.
- 04Probiotics, glutamine, and chronic low-carb diets are not recommended for preventing exercise-induced GI issues.
- 05Starting gut training too close to a race, using glucose-only products, or not training in race conditions are common mistakes to avoid.
Frequently asked
How long does it take for gut training to show results for my athletes or customers?+
Measurable changes in carbohydrate malabsorption can appear after just two weeks. However, for optimal performance in major races, a structured progression of 8–12 weeks is recommended.
What is the maximum carbohydrate intake we should aim for and recommend in our products?+
Grade I evidence supports 60–90 grams per hour, but adapted athletes can tolerate up to 120 grams per hour, particularly with a glucose-fructose combination. Our products should reflect these evidence-based ranges.
Are single-source carbohydrate products, like pure glucose, still effective?+
Glucose-only products cap absorption at around 60 grams per hour due to transporter saturation. To exceed this, products need to include fructose in specific ratios (e.g., 2:1 glucose:fructose) to utilize multiple absorption pathways.
Based on this research, should we incorporate probiotics into our performance supplements?+
The Costa et al. 2025 review found no measurable effect of probiotics on gut barrier injury, inflammation, or symptoms in endurance athletes, regardless of strain type or dosage. Investment in probiotics for this purpose would not be evidence-based.
What are the most common mistakes athletes make that our education or product instructions should address?+
Key mistakes include starting gut training too late, using glucose-only products, not training in race-like conditions (especially heat), introducing new products on race day, and underestimating the body's capacity to adapt beyond initial comfort levels.
Sources
Every briefing is drafted from primary sources — official announcements, vendor blogs, and reputable industry reporting — then edited by our pipeline.
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