What condition are individuals with celiac disease highly intolerant to?

Individuals with celiac disease are highly intolerant to gluten, which is a group of proteins found primarily in wheat, barley, and rye. In celiac disease, the ingestion of gluten triggers an immune response that damages the small intestine's lining, leading to various gastrointestinal and systemic symptoms. This autoimmune reaction can result in nutrient malabsorption, which causes long-term health complications if gluten is not eliminated from the diet.

Understanding the specific intolerance to gluten is crucial for individuals with celiac disease, as even trace amounts can lead to significant health issues. While some individuals may have intolerances or sensitivities to lactose, casein, or soy, these are not related to celiac disease. Therefore, gluten is the primary concern and is the definitive answer to the question.