Sugar Intake Guidelines for Athletes to Avoid Gastrointestinal Symptoms
Athletes should avoid exclusively fructose-containing drinks and instead use a combination of glucose and fructose when consuming carbohydrates during exercise to minimize gastrointestinal symptoms. 1
Carbohydrate Intake Recommendations
Recommended Amounts
- For exercise lasting 1-2.5 hours: 30-60g of carbohydrates per hour 2
- For endurance events lasting longer than 2.5 hours: up to 90g of carbohydrates per hour using multiple transportable carbohydrates (glucose and fructose combination) 2, 3
Carbohydrate Types and Timing
- Multiple transportable carbohydrates: Using a combination of glucose and fructose (rather than glucose alone) improves absorption and reduces gastrointestinal distress 1, 4
- Optimal fructose timing: Add fructose to glucose when:
Strategies to Minimize Gastrointestinal Symptoms
Pre-Exercise Considerations
- Avoid high-fiber foods in the day(s) before competition 1
- Avoid high-fructose foods consumed alone (particularly drinks that are exclusively fructose) 1
- Start exercise well-hydrated to prevent dehydration which can exacerbate GI symptoms 1, 5
During Exercise Considerations
- Ingest carbohydrates with sufficient water to prevent high concentrations in the stomach 1
- Choose drinks with lower carbohydrate concentrations to prevent very high osmolalities 1
- Maintain proper hydration throughout exercise to prevent dehydration-induced permeability issues 5
Concentration and Formulation
- Recommended glucose concentration: 6% solution 4
- Recommended glucose plus fructose: 8-10% solution 4
- Avoid highly concentrated carbohydrate solutions (>500 mOsm/L) as they increase symptom incidence 5
Training the Gut
- Practice nutrition strategies multiple times before race day 1
- Gradually increase carbohydrate intake during training to improve intestinal absorption capacity 4
- Athletes who regularly consume fluids and food during exercise have half the risk of developing GI symptoms compared to those who don't 1
Common Pitfalls and Caveats
- High carbohydrate intake has been positively correlated with nausea and flatulence, but also with better performance in endurance events, suggesting that some mild symptoms may be worth the performance benefit 6
- Avoid NSAIDs (like ibuprofen) before or during exercise as they can increase intestinal permeability and gastrointestinal complaints 1
- Individual tolerance varies significantly - carbohydrate intake rates among athletes range from 6-136g/hour 6
- For very short events (<1 hour), carbohydrate mouth rinse may enhance performance without using the GI tract 4
By following these guidelines, athletes can optimize their carbohydrate intake while minimizing the risk of gastrointestinal symptoms that could impair performance or recovery.