Celiac or coeliac disease is a chronic intolerance of gluten, a protein present in many cereals. Consumption of foods containing gluten leads to a diminished ability of the small intestine to absorb nutrients. Food passes undigested through the body. Symptoms include weight loss, diarrhea, stomach and joint pains and often fatigue. The only effective treatment of the condition is a gluten-free diat i.e. a diet free of products containing wheat, rye, barley, oats and spelt.