Gas evacuated per anus originates by-and-large in the colon, where unabsorbed meal residues are fermented by colonic bacteria. Within subjects, gas output varies in relation to the diet. However, there is a great interindividual variability: gas evacuation in subjects maintained on a similar diet may differ substantially, and this depends on the composition and metabolic pathways of the colonic microbiota. Hence, the volume of gas production and anal evacuation is determined by two main factors: the diet, particularly the amount of fermentable residues, and the individual composition of colonic microbiota. A series of recent studies suggest that some non-absorbable, fermentable meal products (prebiotics) serve as substrate to colonic bacteria and change their composition, thereby producing beneficial effects to the host. These products are fermented by bacteria and at initial intake increase gas production and may induce gas-related symptoms. However, after 7-10 days administration some prebiotics induce an adaptation of intestinal microbiota towards more efficient metabolic pathways with less gas production and the initial symptoms disappear. Some data suggest that phenolic compounds have prebiòtic properties. Aim of the study: to explore the prebiotic effect of a combination of two polyphenol-rich berry extracts (cranberry and chokeberry). Design: single-centre, single arm, open label, proof-of-concept study in healthy subjects. Intervention: a combination of a polyphenol rich extract of chokeberry (Aronia melanocarpa) and a polyphenol rich extract of cranberry (Vaccinium macrocarpon Aiton) will be administered for 18 days. Outcomes: during 2 days immediately before, at the beginning and at the end of the administration phase participants will be put on a standard diet and the following outcomes will be measured: a) number of gas evacuations during daytime for 2 days by means of an event marker; b) perception of digestive sensations by daily scales; c) microbiota composition by fecal analysis; d) metabolites in urine.

Inclusion Criteria:

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Exclusion Criteria:

• gastrointestinal symptoms
• recent (3 months) antibiotic intake
• change in dietary habits 4 weeks before