What is a gluten-intolerant person? Understanding NCGS

January 5, 2026 •

4 min read

Non-celiac gluten sensitivity (NCGS), commonly known as gluten intolerance, is estimated to affect up to 6% of the U.S. population. A gluten-intolerant person experiences adverse reactions to the protein gluten, found in wheat, barley, and rye, differing significantly from the autoimmune response seen in celiac disease.

Quick Summary

A gluten-intolerant person experiences adverse symptoms like bloating and fatigue after consuming gluten, but without the intestinal damage of celiac disease. Diagnosis involves excluding other conditions, and a gluten-free diet typically provides relief.

Key Points

NCGS Definition: A gluten-intolerant person has Non-Celiac Gluten Sensitivity (NCGS), a condition where consuming gluten causes unpleasant symptoms without the autoimmune response or intestinal damage of celiac disease.
Diverse Symptoms: Common symptoms include digestive issues like bloating and pain, neurological effects like brain fog and headaches, and systemic problems such as fatigue and joint pain.
Exclusion Diagnosis: There is no specific test for NCGS; it is diagnosed by first ruling out celiac disease and wheat allergy, then observing a positive symptomatic response to a gluten-free diet.
Strict vs. Flexible Diet: Unlike the lifelong, strict gluten avoidance required for celiac disease, some with NCGS may tolerate small amounts of gluten, though a gluten-free diet is the standard treatment.
Naturally Gluten-Free Foods: A variety of nutritious foods are naturally gluten-free, including fresh fruits, vegetables, meat, dairy, eggs, and grains like rice and quinoa.
Hidden Gluten Awareness: Gluten can be hidden in processed foods like sauces, soups, and certain processed meats, making careful label reading essential for a gluten-free diet.

What is Non-Celiac Gluten Sensitivity (NCGS)?

Non-Celiac Gluten Sensitivity (NCGS) is the medical term for what many people refer to as gluten intolerance or sensitivity. Unlike celiac disease, NCGS is not an autoimmune disorder, and it does not cause permanent damage to the small intestine. It is also distinct from a wheat allergy, which is an immune system overreaction to proteins in wheat and can cause potentially life-threatening symptoms. For a person with NCGS, the ingestion of gluten triggers a variety of unpleasant symptoms that can be disruptive to daily life. The exact cause is not fully understood, but research suggests it may involve an increased permeability of the intestinal lining or a reaction to other carbohydrates found in wheat, known as FODMAPs.

Common Symptoms of Gluten Intolerance

The symptoms experienced by a gluten-intolerant person can vary widely and often mimic those of other digestive conditions, like Irritable Bowel Syndrome (IBS). Symptoms can appear hours or days after consuming gluten. The most frequently reported symptoms include:

Gastrointestinal Issues: Abdominal pain, bloating, gas, diarrhea, constipation, and nausea are common digestive complaints.
Neurological Symptoms: Many people report "brain fog," characterized by mental confusion, difficulty concentrating, and general malaise. Headaches and migraines are also often associated with NCGS.
Systemic Symptoms: Generalized fatigue, joint and muscle pain, and feelings of anxiety or depression can occur.
Skin Problems: Some individuals experience skin rashes, though this is less common than with celiac disease's characteristic dermatitis herpetiformis.

The Difference Between NCGS and Celiac Disease

Understanding the distinction between NCGS and celiac disease is crucial for proper diagnosis and management. While both conditions are triggered by gluten and share similar symptoms, their underlying mechanisms and long-term consequences are very different.


Feature	Non-Celiac Gluten Sensitivity (NCGS)	Celiac Disease (CD)
Cause	A sensitivity or intolerance to gluten, and possibly other wheat components, that does not involve an autoimmune attack.	An autoimmune disorder where the immune system attacks the small intestine in response to gluten.
Intestinal Damage	Does not cause permanent damage to the intestinal lining.	Leads to damage of the villi in the small intestine, impairing nutrient absorption.
Diagnosis	Diagnosis of exclusion: requires ruling out CD and wheat allergy, followed by observing symptom improvement on a gluten-free diet.	Confirmed with specific blood tests (looking for antibodies like tTG-IgA) and a small intestine biopsy.
Genetic Factors	No specific genetic marker is identified, though some genetic components may play a role.	Over 99% of people with CD have the HLA-DQ2 or HLA-DQ8 genes, but these genes are also common in the general population.
Treatment	A gluten-free diet is the primary treatment. Some individuals may be able to tolerate small amounts of gluten.	A strict, lifelong gluten-free diet is essential. Even tiny amounts of gluten can cause damage.

Diagnosis: The Exclusion Process

Diagnosing NCGS is a multi-step process, as there are no definitive biomarkers or tests for the condition. It is a diagnosis of exclusion, meaning other gluten-related disorders must be ruled out first. The process typically involves:

Excluding Celiac Disease: A doctor will order a blood test for celiac-specific antibodies (e.g., tTG-IgA). Crucially, the patient must be consuming gluten for at least six weeks before the test for accurate results. If blood tests are positive or inconclusive, a small intestinal biopsy may be performed to check for intestinal damage.
Excluding Wheat Allergy: An allergy specialist may conduct tests, such as a skin prick test or IgE antibody test, to determine if a wheat allergy is the cause of symptoms.
Gluten-Free Diet Trial: After ruling out celiac disease and wheat allergy, the patient follows a strict gluten-free diet for a period of several weeks. Symptoms are monitored, often using a scale to track severity.
Gluten Reintroduction: If symptoms improve on the gluten-free diet, a gluten challenge is performed, where gluten is reintroduced. If symptoms return, a diagnosis of NCGS is confirmed. This should be done under medical supervision.

Navigating a Gluten-Free Diet

Managing gluten intolerance primarily involves adopting a gluten-free diet to control and minimize symptoms. This requires careful label reading and a strong understanding of which foods contain gluten. While it may seem daunting, many naturally gluten-free foods are available.

Identifying Foods Containing Gluten

Gluten is found in wheat, barley, and rye, as well as their derivatives. A comprehensive list of foods and ingredients to avoid includes:

Grains: Wheat (including spelt, farro, durum, and semolina), barley, rye, and triticale.
Baked Goods: Breads, pasta, cakes, cookies, pastries, and crackers made with wheat flour.
Processed Foods: Many processed items contain gluten as a stabilizer, thickener, or filler. Examples include some sauces, gravies, salad dressings, soy sauce, and certain processed meats.
Beverages: Most beers contain barley malt, and some flavored beverages may contain gluten.
Hidden Sources: Check labels for ingredients like malt extract, brewer's yeast, and hydrolyzed wheat protein. Oats can also be contaminated with gluten during processing, so look for certified gluten-free versions.

Enjoying Naturally Gluten-Free Foods

The good news is that a vast array of delicious and nutritious foods are naturally gluten-free:

Proteins: Fresh meat, poultry, fish, eggs, nuts, and seeds.
Dairy: Most dairy products like milk, butter, and cheese (check for additives in processed versions).
Fruits and Vegetables: All fresh, unprocessed fruits and vegetables.
Legumes: Beans, lentils, and chickpeas.
Gluten-Free Grains and Flours: Rice, quinoa, corn, millet, amaranth, buckwheat, and teff.

For more detailed guidance and resources on eating gluten-free, you can visit BeyondCeliac.org on NCGS.

Conclusion

Being a gluten-intolerant person means experiencing adverse health effects from consuming gluten, though without the severe intestinal damage seen in celiac disease. Symptoms are varied and can impact both digestive and non-digestive systems, including fatigue, headaches, and brain fog. An accurate diagnosis is crucial and involves a process of exclusion, followed by a gluten-free diet trial under a doctor's supervision. With an increasing number of gluten-free food options available, managing NCGS has become more accessible, allowing individuals to significantly improve their quality of life by making informed dietary choices.

Frequently Asked Questions

No, gluten intolerance (NCGS) is a sensitivity that does not cause the intestinal damage characteristic of celiac disease, which is an autoimmune disorder. While symptoms can be similar, the underlying cause and health risks differ.

Common symptoms include bloating, gas, abdominal pain, diarrhea, constipation, headaches, fatigue, and 'brain fog.' These can be triggered by eating foods containing gluten.

Diagnosis is a process of exclusion. A doctor will first test to rule out celiac disease and wheat allergy. If those are negative, a supervised gluten-free diet trial is used to see if symptoms improve, and a gluten challenge is performed to confirm.

A gluten-free diet is the primary treatment for NCGS. While some individuals may tolerate small amounts of gluten, eliminating it entirely often provides the most significant symptom relief. Adherence varies by individual sensitivity.

Yes, chronic fatigue is a common symptom reported by people with NCGS. This can be caused by the body's reaction to gluten and the resulting inflammation.

Gluten can be found in many unexpected products, including sauces, marinades, soy sauce, processed meats like sausage, certain seasonings, and some medications. It is important to read labels carefully.

Many foods are naturally gluten-free, such as fruits, vegetables, unprocessed meat, fish, eggs, dairy, and grains like rice, corn, and quinoa. Specialized gluten-free versions of bread and pasta are also widely available.

Testing for celiac disease is most accurate when a person is regularly consuming gluten. Going gluten-free before testing can lead to an inaccurate negative result, which could prevent the diagnosis of a more serious, lifelong autoimmune condition.