Effects of A2 Dairy Consumption in Celiac Adolescents

The goal of this clinical trial is to evaluate the effect of A2 β-casein-containing milk and dairy product consumption on nutritional status, gastrointestinal symptoms, quality of life, sleep quality, and selected biochemical parameters in adolescents aged 10-18 years with celiac disease. The main questions it aims to answer are: * Does consumption of A2 β-casein-containing milk and dairy products improve gastrointestinal symptoms and quality of life in adolescents with celiac disease? * Does consumption of A2 β-casein-containing milk and dairy products affect nutritional status, body composition, and biochemical parameters compared with standard milk and dairy products? Researchers will compare adolescents consuming A2 β-casein-containing milk and dairy products with adolescents consuming standard milk and dairy products to see if A2 β-casein provides additional benefits. Participants will: * Consume the assigned milk and dairy products during the intervention period. * Attend baseline and follow-up assessments. * Complete dietary records and questionnaires related to gastrointestinal symptoms, sleep quality, and quality of life. * Undergo anthropometric, body composition, hand grip strength, and biochemical assessments.