The purpose of this study is to assess whether green tea or coffee influence the course and life quality of patients with mild to moderately active Crohn's disease.

Inclusion Criteria:

• Women and men ≥ 18 years with signed informed consent,
• Patients with proven Crohn's disease,
• Chronic-active course ≥ 3 months,
• Current CDAI ≥ 150 and ≤ 350,
• All medications for Crohn's disease have to be on a constant dosage for at least 4 weeks prior to study entry (i.e. 5-ASA, steroids),
• Ability of the participant to understand character and individual consequences of the study.

Exclusion Criteria:

• Pregnancy or the wish to become pregnant, breastfeeding,
• Concomitant treatment with methotrexate, azathioprine or 6-mercaptopurine for < 3 months,
• Treatment with TNF-alpha-antagonists, cyclosporine or tacrolimus < 4 weeks prior to study entry,
• Participation in another study within the last 4 weeks,
• Ulcerative colitis or indeterminate colitis,
• Infectious colitis, including cytomegalovirus or Clostridium difficile induced colitis,
• Colitis for other reasons like known diverticulitis, radiation colitis, ischemic colitis or microscopic colitis,
• Malabsorption syndromes, lactose intolerance, celiac disease, exocrine pancreas insufficiency,
• Bleeding hemorrhoids,
• Other inflammatory or bleeding disorders of the colon and intestine, or diseases that may cause diarrhea or gastrointestinal bleeding,
• Intolerance / aversion to tea and/or coffee,
• Current treatment with antibiotics.