Nausea and gastrointestinal issues during exercise? Fructose malabsorption might be the cause!

Are you unknowingly dealing with an issue that regularly ruins your workouts? Especially when it really counts? Many endurance athletes know the feeling: gels, sports drinks, soda during a race—and suddenly your stomach shuts down. The first suspect is always the product. “I just can’t handle XYZ!”

What's almost always missing: 👉 A look at the ingredient list.

If it contains fructose (a simple sugar found in many energy products), that alone could be the culprit. This is because 30–40% of people in the Western world have fructose malabsorption (FMA).

It's not dangerous, but when you're under stress, it can really throw your stomach and intestines off balance. The consequences:

• Nausea
• Stomach cramps
• Flatulence
• Diarrhea

Why do so few athletes know that they have fructose malabsorption?

It's simple: you only have problems when you're under stress because blood flow to the intestines decreases at that time.

How can you tell if you have fructose malabsorption?

• Self-test during training: Simply try a fructose-containing gel or drink while exercising at high intensity.
• Medical: Fructose breath test (H₂ breath test) performed by a gastroenterologist. But be careful: we know countless athletes who test negative but experience the aforementioned problems during exercise.

What if you have fructose malabsorption?

No need to worry. You can continue your sports activities as usual. But you should switch to sports nutrition products that contain little or no fructose.

Why is fructose in almost everything?

It’s cheap, has a rich flavor, and allows for high carbohydrate content in the product. But that’s product logic—not athlete logic.

Do dual-carb products make sense for you?

If you have FMA: Only to a limited extent
Dual Carb = Glucose + Fructose. Two “gates” in the small intestine:
SGLT1 → Glucose
GLUT5 → Fructose
The problem: For many athletes, the fructose gate is a deal-breaker. It triggers symptoms.

What makes SQUEEZY different?

• We develop products for competitive situations—not for the lab.
  No fructose or very little fructose
• No hidden sources of fructose (e.g., sucrose)
• No artificial sweeteners or colors
• no unnecessary vitamins and minerals
• always with a focus on low osmolarity (the number of dissolved particles in a liquid, such as a gel, liquid, or powder)

Our Basic Formula products go one step further:

• a small amount of glucose
• Low-osmolarity maltodextrin
• No artificial flavors, just a subtle citrus taste
• Sodium & Potassium

What sounds like "boring" has simply swept away the stomach problems of many athletes over the past three years.

If this article has helped you better understand what’s going on in your body or has given you a new perspective, please let us know in the comments.

For more information on fructose intolerance and glucose vs. fructose, see here as well.