Tryptophan is an important amino acid, a building block of proteins, that our body needs. This study is testing how L-tryptophan affects people with celiac disease (CeD)gluten-free diet (GFD) for a year. This study includes 50 participants, aged 18 to 75, who will take either L-tryptophan or a placebo (a pill with no active medicine) for three weeks.

Participants will visit the clinic three times. At the start, they will get all their study pills and learn about a special diet. They will fill out questionnaires about their diet and symptoms, give blood, stool, and urine samples, and have a small medical procedure called an endoscopy to check their intestine.

• The study lasts for 3 weeks.
• Participants will need to visit the clinic 3 times.
• This study includes medical procedures like endoscopy.