Can Quorn Cause Upset Stomach? Understanding Mycoprotein's Digestive Impact

November 8, 2025 •

3 min read

According to a 2018 analysis of self-reported adverse reactions collected by the Center for Science in the Public Interest, over 1,600 people experienced gastrointestinal issues after eating Quorn products. While generally safe for most, this shows that for some individuals, Quorn can cause upset stomach, bloating, or other digestive problems.

Quick Summary

Some individuals report gastrointestinal distress after consuming Quorn products, with symptoms ranging from mild nausea to severe abdominal pain and vomiting. This reaction is primarily linked to the product's high fiber content or an individual's sensitivity to mycoprotein, its core ingredient.

Key Points

High Fiber Content: Quorn's main ingredient, mycoprotein, is rich in fiber, which can cause bloating, gas, and stomach upset, especially for those not used to a high-fiber diet.
Mycoprotein Sensitivity: A smaller number of individuals may have an intolerance or allergy to mycoprotein, a fungi-derived protein, resulting in gastrointestinal issues or other allergic reactions.
Start Gradually: To minimize the risk of digestive issues, introduce Quorn into your diet in small amounts to allow your system to adjust to its high fiber.
Check for Other Allergens: Some Quorn products contain other potential allergens, such as egg or gluten, which could be the actual cause of a reaction.
Consult a Doctor for Severe Reactions: Seek professional medical advice for persistent symptoms or signs of a severe allergic reaction like hives or breathing difficulties.
Track Your Reactions: Keeping a food diary can help identify if Quorn is consistently causing your digestive issues or if other factors are involved.

What is Mycoprotein and Why Does it Cause Upset Stomach?

Quorn's primary ingredient is mycoprotein, a type of single-cell protein derived from the fungus Fusarium venenatum. While a nutritious and sustainable protein source, it is not without potential drawbacks for certain digestive systems. The two main reasons mycoprotein can lead to an upset stomach are its high fiber content and potential for sensitivity or allergic reactions.

The Impact of High Fiber

Mycoprotein is naturally very high in dietary fiber. For individuals unaccustomed to such high fiber intake, or those with underlying conditions like Irritable Bowel Syndrome (IBS), this can overwhelm the digestive system. A sudden increase in fiber can lead to:

Gas and Bloating: Fiber is fermented by gut bacteria in the large intestine. Rapid or excessive fermentation produces gas, causing bloating and discomfort.
Diarrhea: The high fiber content can speed up the transit of food through the intestines, leading to looser stools or diarrhea.
Abdominal Cramps: Increased gut activity and fermentation can cause painful cramping in some people.

Mycoprotein Sensitivity and Allergic Reactions

For a smaller number of people, the issue is not just the fiber but a specific sensitivity or allergy to the mycoprotein itself. Mycoprotein is a mold, and those with pre-existing mold allergies may have a higher risk of reacting to it. Reported reactions to Quorn's mycoprotein are varied and can include both gastrointestinal and systemic symptoms:

Gastrointestinal Symptoms: Nausea, vomiting, severe abdominal pain.
Allergic Symptoms: Hives, itching, swelling of the throat or mouth, and in rare cases, anaphylaxis.

Quorn vs. Other Meat Alternatives: A Comparison

To better understand why Quorn might cause digestive issues when other alternatives do not, a comparison is helpful. While Quorn is high in fiber, alternatives like tofu and seitan have different compositions and effects.


Feature	Quorn (Mycoprotein)	Tofu (Soy-based)	Seitan (Wheat-based)
Primary Ingredient	Fusarium venenatum (Fungus)	Soybeans	Wheat gluten
Key Characteristic	High fiber, fermented	Fermentable, contains oligosaccharides	High protein, processed wheat
Potential for Upset Stomach	Higher risk due to fiber and mycoprotein sensitivity	Lower risk, but soy intolerance or high FODMAP sensitivity possible	Unsuitable for gluten intolerance; otherwise generally low risk
Processing Level	Processed through fermentation	Minimally to moderately processed	Highly processed

How to Manage Digestive Issues with Quorn

If you suspect Quorn is causing you digestive distress, there are several strategies you can employ to mitigate the effects:

Start Small: When first introducing Quorn into your diet, begin with small portion sizes. This allows your digestive system to adapt to the higher fiber content gradually.
Hydrate Well: Increase your water intake when consuming high-fiber foods to help your body process the fiber more smoothly.
Consider Other Ingredients: Some Quorn products contain other common allergens like egg, milk, or wheat, which could be the source of your issues. Always check the full ingredients list.
Consult a Professional: If symptoms are persistent or severe, it is advisable to speak with a doctor or a registered dietitian. They can help determine if you have a specific allergy or intolerance to mycoprotein or another ingredient.
Monitor Your Diet: Keep a food diary to track when you eat Quorn and what, if any, symptoms follow. This can help you pinpoint the exact cause of your discomfort.

What to Do If You Have a Severe Reaction

If you experience symptoms of a severe allergic reaction, such as swelling of the throat, difficulty breathing, or anaphylaxis, seek immediate medical attention. In the US, the manufacturer's labels now state that there have been "rare cases of allergic reactions" to mycoprotein, acknowledging the risk. The Center for Science in the Public Interest (CSPI) has documented numerous severe reactions and encourages reporting issues. You can report adverse reactions on their website: Quorn | Center for Science in the Public Interest.

Conclusion

While Quorn is a nutritious and environmentally conscious meat alternative, the potential for an upset stomach is a legitimate concern for a subset of the population. The primary culprits are its high dietary fiber, which can cause discomfort for those with sensitive digestive systems, and mycoprotein, which can trigger allergic or intolerance reactions in a small number of individuals. By introducing Quorn gradually, monitoring portion sizes, and being aware of the symptoms, many can still enjoy this meat-free option. However, if severe or persistent digestive problems occur, seeking professional medical advice is the safest course of action. Understanding these potential effects allows for a more informed and mindful approach to incorporating Quorn into your diet.

Frequently Asked Questions

Quorn can cause stomach pain due to its high fiber content, which can lead to increased gas and bloating from fermentation in the large intestine. Additionally, some people have an intolerance or allergy to the mycoprotein (a fungus) that makes up Quorn, causing a negative reaction.

An upset stomach from Quorn is not a widespread issue, but it does affect a subset of consumers. Reports of gastrointestinal issues are more common than severe allergic reactions, often linked to the high fiber content.

Gastrointestinal symptoms related to Quorn, such as nausea and diarrhea, have been reported to occur within 8 hours of consumption. For most, symptoms dissipate within 24 hours, but this can vary depending on the individual and severity of the reaction.

Yes, it is possible to have an allergy to Quorn's mycoprotein, a protein derived from a fungus. Individuals with existing mold allergies may be more susceptible. Symptoms can include hives, swelling, and even severe anaphylactic reactions in rare cases.

No, Quorn is not difficult for everyone to digest. The difficulty arises in individuals who are sensitive to its high fiber content or have an existing intolerance or allergy to mycoprotein. Most people can consume it without any problems.

To prevent an upset stomach, try introducing Quorn in small portions, drinking plenty of water, and checking the ingredient list for other potential allergens like egg or gluten. If you have a sensitive digestive system, a gradual approach is key.

Yes, even the vegan version of Quorn contains mycoprotein and is high in fiber, so it can still cause digestive issues for sensitive individuals. The primary difference is the use of potato protein instead of egg white as a binder, but the core mycoprotein component remains.