Why energy gels can cause stomach problems
Energy gels are a convenient way for endurance athletes to consume carbohydrates quickly, but their composition and use during strenuous activity can lead to gastrointestinal (GI) issues. During a high-intensity run, your body prioritizes sending blood to your working muscles, diverting it away from your digestive system. This makes the GI tract more sensitive and less efficient at processing food, especially concentrated, high-sugar sources like energy gels. Several specific factors contribute to this discomfort:
High Sugar Concentration and Osmolality
Most traditional energy gels are essentially concentrated sugar water, designed to deliver a rapid energy boost. However, this high concentration, or osmolality, can be a major irritant. To properly digest and absorb this sugar, your body pulls water from your bloodstream into your gut. If you don't drink enough water with a gel, this process can lead to bloating, cramping, and diarrhea as your body attempts to dilute the high sugar load.
The Fructose Factor
Many gels contain a mix of different carbohydrates, including glucose (or maltodextrin) and fructose, to increase the total amount of carbs the body can absorb per hour. While this dual-carb strategy can be effective, fructose can be a significant trigger for GI distress in sensitive individuals. As a FODMAP, it can be poorly absorbed in the small intestine and ferment in the large intestine, producing gas and leading to cramping and bloating. For those with conditions like IBS, this can be particularly problematic.
Artificial Ingredients and Additives
Beyond the primary carb source, the artificial flavors, sweeteners, and preservatives found in some commercial gels can also upset a sensitive stomach. Some athletes find they react poorly to these ingredients, experiencing bloating and general discomfort. Opting for gels with cleaner, more natural ingredient lists can sometimes mitigate these issues.
The Role of Caffeine
For an extra kick, many gels include caffeine. While beneficial for performance, caffeine is also a known gut motility stimulant. This can increase the urgency to use the restroom during a run and is not ideal for runners prone to digestive issues.
Not all running gels are bad for the stomach
The good news is that advancements in sports nutrition offer alternatives designed to be gentler on the digestive system. You can mitigate or avoid GI issues by being mindful of the product's formulation and your consumption strategy.
Comparing Different Gel Types for Sensitive Stomachs
| Feature | Traditional Gels | Isotonic Gels (e.g., SIS) | Hydrogels (e.g., Maurten) | Whole-Food Gels (e.g., Hüma) |
|---|---|---|---|---|
| Potential GI Impact | High, especially without water | Lower due to pre-dilution | Very low, bypasses stomach | Low, natural ingredients |
| Hydration Needs | Requires water for dilution | No extra water needed | Can be taken with or without water | Take with water for easier absorption |
| Carb Source | Typically maltodextrin and fructose | Maltodextrin, specific ratios | Encapsulated carbs | Real fruit purée, seeds, maple syrup |
| Ideal Use Case | Best for athletes with trained guts | Runners who dislike carrying extra water | High-carb fueling needs | Runners prioritizing natural ingredients |
How to Avoid Stomach Upset from Running Gels
- Practice in training. Your gut is trainable, just like your muscles. Experiment with different brands, types, and timings during your long training runs—not on race day. This allows your body to adapt to the gel's composition and the fueling strategy.
- Stay hydrated. If using a traditional gel, always take it with water. This is critical for dilution and absorption. Isotonic and hydrogels reduce this need, but consistent hydration remains vital for performance and digestion.
- Choose the right gel. If you have a sensitive stomach, consider experimenting with hydrogels (like Maurten, which encapsulates carbs to bypass the stomach) or whole-food gels (like Hüma, made with real fruit and chia seeds).
- Time and dose correctly. Instead of taking one large dose, opt for smaller, more frequent intakes. For example, sip the gel over a few minutes rather than consuming it all at once. Take your first gel before you feel fatigued, typically 60-90 minutes into a long run, and then regularly thereafter.
- Evaluate other factors. Look beyond the gel. Check if the product has caffeine, which may exacerbate issues. Consider your pre-run meal (avoiding high-fat, high-fiber foods) and overall hydration.
Conclusion
While the concentrated nature of energy gels can lead to stomach upset for some runners, the gels themselves are not inherently bad for the stomach. The root cause of GI issues often lies in a combination of reduced blood flow during exercise, high sugar concentration, inadequate hydration, and individual sensitivities to specific ingredients like fructose or caffeine. By understanding these factors and implementing a strategic approach—including gut training, proper hydration, and choosing a suitable gel type—most athletes can successfully use energy gels without negative side effects. Testing different products and consumption methods during training is the most effective way to find what works for your body and fuel your performance without discomfort.
Learn more about training your gut to absorb carbohydrates effectively during running from this resource: How Do I Get Used To Gels & Fuelling While Running?.
