Best Energy Gels For Sensitive Stomachs

Key Takeaways:

• High-fructose content and hypertonic gels are the most common causes of GI distress during runs.

• Isotonic and hydrogel gels are the gentlest options for sensitive stomachs.

• Whole-food gels can be easier to digest for some runners due to their natural carbohydrate matrix.

• Always train your gut in long runs; start with half a gel (~15 g/hour) and gradually increase.

• Never try a new gel on race day, consistency in format and carbohydrate load is key to avoiding GI issues.

Nothing derails a run faster than nausea, cramping, bloating, or an urgent bathroom stop caused by an energy gel. If you've ever abandoned your fuelling plan mid-race because your stomach couldn't tolerate it, you're not alone. Gastrointestinal (GI) symptoms are extremely common in endurance sport, with research suggesting that 30-90% of endurance athletes experience some form of GI distress during training or competition, ranging from mild discomfort to severe symptoms such as diarrhoea and vomiting¹.

The good news is that energy gels aren't always the problem. In many cases, GI issues are linked to specific carbohydrates used, hydration, sweeteners, caffeine content, or the overall formulation of the gel. Understanding these factors can make a significant difference to how well your gut tolerates fuelling during exercise.

In this guide, we'll explain why some gels are more likely to cause stomach issues than others and explore the best energy gels for sensitive stomachs. Whether you're a first-time marathon runner or an experienced athlete looking for a more gut-friendly option, there are effective solutions that can help you fuel with confidence and keep your race on track.

Quick Answer: Best Energy Gels for Sensitive Stomachs

For runners with a sensitive gut, certain gel formats are much gentler on the stomach than others. Isotonic gels (e.g. SiS Go Isotonic or High5 Energy Gel Aqua) are pre-diluted and don’t require extra water, reducing osmotic stress². Hydrogel gels (e.g. Maurten Gel 100) use a polysaccharide matrix to slow digestion and lower gut load, with strong evidence for GI tolerance³˒⁴. Low-fructose or fructose-free gels (e.g. Koda Nutrition Energy Gels) minimise fermentation-driven bloating, while whole-food gels (e.g. Näak Boost Energy Gel or SAP Good Energy Gel) rely on natural carbohydrate sources like maple syrup or agave powder, which some runners find easier to digest⁵˒⁶. Whatever the type, always test gels in training first,  never try a new formula on race day.

Why Do Energy Gels Upset Your Stomach?

Energy gels can be a digestive challenge for many runners, but the problem is usually not the gel itself,  it’s how specific ingredients and formulations interact with your gut during exercise. One key factor is osmolality. Most standard gels are hypertonic, meaning they are more concentrated than blood. This draws water into the gut to dilute the solution, which can slow gastric emptying and lead to bloating or nausea, especially if you haven’t consumed enough water²˒⁴.

Fructose load is another common culprit. Gels high in fructose can overwhelm the GLUT-5 transporter in the small intestine. Unabsorbed fructose ferments in the colon, causing gas, bloating, and diarrhoea, particularly in runners with IBS or fructose sensitivity⁵˒⁷.

Caffeine can accelerate gut motility in some athletes, triggering urgent bowel movements mid-run, while artificial sweeteners like sorbitol or maltitol are osmotically active and may induce diarrhoea at higher doses⁸.

Finally, running mechanics contribute to GI distress. During high-intensity exercise, blood flow is prioritised to the muscles rather than the digestive tract, compounding discomfort from poorly tolerated gels. Understanding these mechanisms helps runners make informed choices and select gels that are gentler on the stomach¹˒⁹.

What to Look for on a Gel Label (If You Have a Sensitive Stomach)

For sensitive runners, natural or whole-food gels, using ingredients like maple syrup or honey  are often the gentlest on the gut⁶. Another option is isotonic gels. These are  pre-diluted gels that reduceosmotic stress². Pay attention to fructose position: if it’s first or second, it may be too high⁵. Avoid artificial sweeteners such as sorbitol, maltitol, or xylitol, which can cause diarrhoea⁸. Start with non-caffeine gels and aim for a balanced carbohydrate ratio (Glucose/maltodextrin:fructose ~2:1)⁶.

The Best Gel Types for Sensitive Stomachs

For runners with a sensitive gut, choosing the right gel format can make a huge difference.

Whole-Food Gels

Whole-food gels made from ingredients such as maple syrup, honey, dates or agave powder may be better tolerated in some runners due to their less processed carbohydrate structure and natural food matrix. This can support more gradual digestion and reduce rapid osmotic shifts in the gut, which are often linked to GI discomfort during exercise⁶. Some formulations also provide small amounts of micronutrients and polyphenols, which may support overall gut function⁶. Brands such as SAP, Nectar Sport, Maple Movement Naak and UnTapped are commonly used by athletes seeking a more natural fuelling option, particularly those sensitive to highly refined or multi-ingredient gels.

Isotonic Gels

Isotonic gels are pre-diluted to match the osmolality of blood, so they require no extra water and place minimal osmotic stress on the gut². This helps reduce bloating and nausea. The most widely used examples are  SiS Go Isotonic, 226ERS Isotonic Energy Gel or High5 Energy Gel Aqua, available through Aid Station.

Hydrogel Gels

Hydrogel gels encapsulate carbohydrates in a sodium alginate/pectin matrix that gels in the stomach. This structure slows gastric emptying, lowers osmotic load, and allows higher carbohydrate intake with fewer GI symptoms. Clinical evidence shows improved tolerance and performance compared with standard gels³˒⁴. Maurten Gel 100 and Gel 160 are leading options.

Low-Fructose / Glucose-Only Gels

For runners with confirmed fructose sensitivity, low-fructose or glucose-only gels such as Koda Nutrition Energy Gels, reduce fermentation-driven bloating and diarrhoea⁵˒⁷. These gels are gentler but have a lower per-hour carbohydrate ceiling (~60g/hour).

By selecting the right format, runners can fuel effectively while keeping GI distress to a minimum.

What Gels to Avoid if You Have a Sensitive Stomach

Sensitive runners should focus on formulation rather than brand. High-fructose gels (fructose as the first or second ingredient) can overwhelm intestinal transporters and cause bloating or diarrhoea⁵˒⁷. Highly concentrated or hypertonic gels taken without adequate water may slow gastric emptying and increase gut discomfort²˒⁶. Gels containing artificial sweeteners such as sorbitol, maltitol, or xylitol are osmotically active and may trigger diarrhoea⁵. Caffeine gels can accelerate gut motility, causing urgency in some athletes⁸.
Thick, paste-like gels may increase nausea for runners with texture sensitivity¹˒⁹.

Train Your Gut - It Gets Better

Gastrointestinal tolerance to carbohydrates during exercise is highly trainable. Consistent exposure in training leads to significant adaptation, reducing symptoms over time¹˒⁹. Start with lower doses, around half a gel or ~15 g/hour, and gradually increase over 4-6 weeks. Practise fuelling during long runs, ideally at race-day intensity, and in conditions similar to your event, including heat and hydration strategies. Framing gut training as an investment rather than a burden allows runners to improve tolerance, optimise fuelling, and reduce GI distress on race day, ensuring that nutrition supports rather than sabotages performance¹˒⁹.

Find Your Gut-Friendly Gel

Sensitive stomachs don’t mean you can’t fuel with gels,  it’s about choosing the right formulation. Start with isotonic or hydrogel gels, and avoid high-fructose or artificial sweetener-heavy options²⁻⁵˒⁷. Consistently train your gut in long runs and never trial a new gel on race day¹˒⁹. With the right approach, you can fuel effectively while minimising GI distress.

Explore Aid Station’s range of isotonic and hydrogel gels, and find the formula your stomach will actually thank you for.

Ash Miller
Dietitian and Nutritionist (Masters)
Bachelor of Physical and Health Education
Instagram: @ashthomo_nutrition

References

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5. Gibson PR. The evidence base for efficacy of the low FODMAP diet in irritable bowel syndrome: is it ready for prime time as a first-line therapy? J Gastroenterol Hepatol. 2017 Mar;32 Suppl 1:32-35. doi: 10.1111/jgh.13693. PMID: 28244668.

6. Podlogar T and Wallis G.A (2022). New Horizons in carbohydrate research and application for endurance athletes. Sports Medicine 52.

7. Monash University. Low FODMAP Diet. Monash FODMAP. Available from: https://www.monashfodmap.com/

8. Nehlig A. Effects of coffee on the gastrointestinal tract: A narrative review and literature update. Nutrients. 2022;14(2):399.

9. Costa RJ, et al. Systematic review: exercise-induced gastrointestinal syndrome-implications for health and intestinal disease. Alimentary Pharmacology & Therapeutics. 2017;46(3):246-265.

Disclaimer:
The content in this blog is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak with your doctor or allied health team before changing your diet, exercise, or taking supplements, especially if you have a health condition or take medication. Please use this information as a guide only. Aid Station doesn't take responsibility for individual outcomes.