We recruited 25 of the 40 participants from intended study population. Recruitment in new populations requires an METC amendment.

RATIONALE: The underlying etiology in inflammatory bowel diseases such as Ulcerative Colitis is not yet fully understood. Studies suggest a relation between higher intestinal permeability and aberrant changes of the epithelium. Dysbiosis of the intestinal microbiota might be the cause. Probiotics may restore the balance of the intestinal microbiota. In theory this could improve intestinal permeability and therefore reduce disease activity and maintain remission in patients with Ulcerative Colitis.

OBJECTIVE: To investigate whether a specifically designed multispecies probiotic mixture (ecologic 825®), as adjuvant therapy, can contribute to an improvement of intestinal permeability, microbiota composition, disease activity and inflammatory markers in ulcerative colitis.

STUDY DESIGN: 12-wk placebo-controlled randomized double-blind intervention with 2 parallel arms.

STUDY POPULATION: Adults diagnosed with left sided Ulcerative Colitis or Pancolitis in remission or mild stage of the disease. For inclusion of the patients the Patient Simple Clinical Colitis Activity Index (P-SCCAI) will be used.

INTERVENTION: Patients will receive either two daily dosages of 3 g of Ecologic® 825 or two daily doses of 3 g of the placebo, containing only the carrier material (both produced by Winclove Probiotics).

MAIN STUDY PARAMETERS/ENDPOINTS: Main study parameter is intestinal permeability measured by several techniques: the lactulose/mannitol absorption test (L/M test), LPS levels in blood serum and faecal zonulin. Secondary, inflammation will be measured from faecal calprotectin and blood c-reactive protein (CRP) levels. Furthermore samples will be stored to measure cytokine concentrations in serum and to analyse the microbial composition of the faecal samples using the HITchip. For the disease related quality of life the irritable bowel disease questionnaire (IBD-Q) and SF-36 will be used. All parameters will be measured at three time points; t=0, t=6 and t=12 weeks.

Inclusion Criteria:

• Diagnosed Ulcerative Colitis (left sided UC or pancolitis)
• Age 18-65 (because microbiota change at older age)
• Stable disease activity (clinical remission with CRP levels <10mg/L and calprotectin <100 ug/g) as measured at baseline
• Mild disease activity (P-SCCAI <5)
• Mesalazine medication as only medication for UC with a maximum intake of 2.4 g/day

Exclusion Criteria:

• History of intestinal surgery that might interfere with the outcome of the study
• Diabetes Mellitus (medication dependent)
• Current use of antibiotics
• Current use of corticosteroids (30 days prior to the first baseline measurement).
• Treatment with other medication besides mesalazine (NSAIDs, topical or systemic steroids, immunosuppressive drugs or aspirin) one week prior the first baseline measurement.
• Use of other pre- and probiotics and not willing to stop these 2 weeks before the intervention period
• Hypersensitivity or allergy to milk protein, soy protein and gluten
• Alcohol abuse (male more than 14 servings a week, female more than 7 servings a week)
• Female patients: currently pregnant or breast-feeding or intending to become pregnant during the study
• Patients foreseen to need GI surgery during the study period
• Patients with a history of cancer