How do I know if I have a food intolerance?

This is an increasingly common question, especially in an era dominated by social media stories and diets focused on food intolerances. With an abundance of information available, it can be challenging to sift through and determine whether your own symptoms warrant special attention. In this article, we’ll answer some of the most common questions to help you better understand this sometimes complex and uncomfortable topic.

What is a food intolerance?

A food intolerance is an adverse reaction to a food or one of its components that does not involve the immune system (unlike allergies). These intolerances are often characterized by difficulty digesting or metabolizing certain compounds. While the symptoms of food intolerances can be unpleasant, they are not life-threatening.[1][2]

The most common food intolerances[3] are:

• Lactose
• Gluten (non-celiac)
• Food additives (sulfites, monosodium glutamate)
• Histamine
• FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, polyols)

What are the symptoms of a food intolerance?

Symptoms vary from person to person, even for the same intolerance. The most common symptoms include[4]:

• Bloating, gas, abdominal pain
• Diarrhea or constipation
• Chronic fatigue
• Migraines
• Skin rashes or eczema

How can you tell if you’re intolerant to a food?

Connecting a specific food with a symptom is not always straightforward. While lactose intolerance is relatively easy to diagnose, many other intolerances lack specific diagnostic tests.[5] Currently, there are no specific tests to diagnose intolerances to gluten, histamine, or FODMAPs.[6][7] Therefore, it’s recommended to closely monitor your diet and your body’s reactions. Keeping a food journal—where you record meals, symptoms, and their intensity—is an essential first step.

How can a food intolerance be treated?

The progression of a food intolerance is rarely predictable. The most promising way to reduce your symptoms is to partially or completely eliminate the food causing them.

The elimination diet, conducted under the guidance of a healthcare professional, is the most used method to confirm or rule out a food intolerance. This involves temporarily removing (often for a few weeks, until symptoms disappear) foods suspected of causing discomfort. These foods are then gradually reintroduced one at a time while observing the body’s reactions.[8]

Do problematic foods need to be eliminated permanently?

Not always! After completing an elimination diet and identifying problematic foods, many people can consume small amounts without triggering symptoms. Everyone’s tolerance level is different. This threshold can be determined during the reintroduction phase of the elimination diet.

People who are lactose intolerant can use a lactase supplement to help digest lactose and prevent symptoms.

When should you consult a healthcare professional?

If your symptoms are frequent, affect your quality of life, or if you suspect multiple problematic foods, it’s best to consult a registered dietitian or nutritionist. This helps ensure an accurate diagnosis, avoid unnecessarily restrictive diets, and maintain a balanced diet.

A personalized approach for long-term wellness

Food intolerances are complex and can easily be mistaken for other digestive issues. Therefore, personalized support is crucial for identifying triggers, finding practical solutions, and maintaining both quality of life and a varied diet.

• [1] Ellis, E. (2020). Food allergies and intolerances. Academy of nutrition and dietetics.
• [2] Government of Canada. (2023). Food Allergies and Intolerances.
• [3] National Health Service. (2022). Food intolerance.
• [4] Idem
• [5] Glinski, S. (2025). Comment tester l’intolérance au lactose ? Fondation canadienne de la santé digestive.
• [6] Adel, K. (2020). Tout savoir sur l’intolérance à l’histamine. Médecins francophones du Canada.
• [7] Fondation canadienne de la santé digestive. (2024). Comprendre les FODMAP. Que sont les FODMAP ?
• [8] Gordon, B. (2019). What is an elimination diet ? Academy of nutrition and dietetics.

How do I know if I have a food intolerance? is a post from Nautilus Plus. The Nautilus Plus blog aims to help people in their journey to fitness through articles on training, nutrition, motivation, exercise and healthy recipes.
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