Inclusion criteria  Clinically healthy subjects (i.e. lack of symptoms that may suggest IBD) that are enrolled to the GEM project, with a high faecal calprotectin (FC)>100μg/g or increased microbiome risk score. Younger than 25 years of age, in order to maximize future risk of developing CD. Lewis score on panenteric video capsule endoscopy (VCE)<350 and no overt ulcerations (other than aphthous ulcerations) in the colon.  Exclusion Criteria:  Ulcerative colitis (UC) or IBD-unclassified (IBDU) diagnosis The use of antibiotics in the preceding month Prior intestinal resection Pregnancy (and up until six months after giving birth) Celiac disease or Diabetes Weight loss or weight gain by more than 20% body weight in the last 3 months Extraintestinal manifestations (Arthritis/arthralgia, iritis/uveitis, skin/mouth lesions, peri-anal disease, Other fistula). Underweight (children <3th BMI percentile, adult above the age of 18 years: BMI<18.5 kg/m2).