The goal of this clinical trial is to learn if omega-3 fatty acid supplements (n-3 PUFAs) can help reduce inflammation and promote intestinal healing in adults newly diagnosed with celiac disease (CD).

Celiac disease is a chronic autoimmune disorder where eating gluten-a protein found in wheat-triggers an immune response that damages the lining of the small intestine. This damage causes inflammation and symptoms such as stomach pain, diarrhea, and nutrient absorption problems. The only current treatment is a strict gluten-free diet (GFD), which can help most people recover, but some continue to have inflammation and symptoms.

This study will test whether supplementing with 2.4 grams of n-3 PUFAs daily for three months, alongside starting a gluten-free diet, reduces inflammation in the blood and intestine more effectively than the gluten-free diet alone.

Participants will:

Be adults recently diagnosed with celiac disease who have not yet started a gluten-free diet

Be randomly assigned to one of two groups:

One group will receive omega-3 supplements containing 2,400 mg of n-3 PUFAs daily (2,000 mg DHA and 400 mg EPA) The other group will receive a placebo (a pill with no active ingredients that looks like the supplement) Take the assigned supplement every day for 3 months while following a supervised gluten-free diet Visit the clinic regularly for checkups, blood tests, and monitoring of symptoms and diet adherence Provide blood and stool samples before and after the intervention to measure inflammation and changes in gut bacteria A subgroup of participants will undergo small intestinal biopsies to assess local inflammation and healing

The study aims to answer these main questions:

Does omega-3 supplementation change the fatty acid composition in blood cells? Does it reduce markers of inflammation in the blood and small intestine? Does it improve the diversity and health of gut bacteria in the intestine? Does it help the small intestine heal faster compared to diet alone?

Researchers will measure inflammation by analyzing immune signaling pathways, oxidative stress markers, and antioxidant activity in blood cells. They will also study the composition of the gut microbiota and its metabolites. These detailed measurements will help understand how omega-3 fatty acids may influence the immune response and gut health in celiac disease.

This is a randomized, double-blind, placebo-controlled crossover study. This means participants and researchers will not know who receives the supplement or placebo during the study period, reducing bias and improving the reliability of the results.

This study is important because it could offer a simple, additional treatment to improve recovery in celiac disease beyond the gluten-free diet. If omega-3 supplements are shown to reduce inflammation and support healing, they could become a valuable part of managing this chronic condition.

Participation is voluntary, and participants can leave the study at any time without affecting their medical care. All participants will be closely monitored to ensure safety throughout the study.

Inclusion Criteria:

• Adult patients aged 18 to 65 years, Newly diagnosed with celiac disease confirmed by serology and intestinal biopsy, Not yet started gluten-free diet (GFD), Willingness to adhere to a supervised gluten-free diet during the study, Able to provide informed consent

Exclusion Criteria:

• Previous or current adherence to a gluten-free diet, Use of n-3 PUFA supplements or other dietary supplements influencing inflammation within the last 3 months, Presence of other autoimmune, inflammatory, or gastrointestinal diseases (e.g., Crohn's disease, ulcerative colitis), Pregnancy or breastfeeding, Severe chronic illnesses that may interfere with the study or outcomes (e.g., uncontrolled diabetes, cancer), Allergy or intolerance to fish oil or components of the supplement, Use of immunosuppressive or anti-inflammatory medication within the last 3 months

De-identified individual participant data (IPD) collected during this study will be made available to qualified researchers upon reasonable request after publication of the primary study results. Data sharing requests will be reviewed by the study steering committee to ensure appropriate use and compliance with ethical and privacy regulations. Data will be shared through a secure data repository, and a data use agreement will be required.