Impact of Galacto-Oligosaccharides on Adult Microbiome

Inclusion Criteria: * Age 18-55 years, * Healthy participants, both male and female * BMI in the normal and overweight range 18.5 ≤ BMI ≤ 29.9 kg/m2 * Able to understand and to sign a written informed consent prior to study enrolment Exclusion Criteria: * Known chronic diseases or conditions for which the investigators/investigation team deem as not suitable for study participation, * Known food allergy and intolerance e.g. lactose intolerance, * Habitually, have \< 5 spontaneous bowel movements on average per week, * Chronic or recurrent diarrhoea with spontaneous bowel movements \> 2 per day * Prior gastrointestinal surgery (apart from appendectomy or herniotomy), * Received systemic antiviral/antibacterial/antifungal therapy during the 3 months prior to study enrolment, * Medications or supplements that are known to alter gut function or microflora i.e. acid antisecretory drugs, pre-/probiotics, laxative during the 4 weeks prior to study enrolment, * Anti-hyperlipidaemic, antihypertensive medications and/or anticoagulant agents, * Currently participating in another interventional clinical trial or research project, * Alcohol intake \> 2 servings per day; specifically, a serving is 0.4 dl of strong alcohols, 1 dl of red or white wine, or 3 dl of beer. Or other chronic substance abuse, * Changing diet patterns due to travelling and staying abroad for more than two weeks (Asia, Africa, or Latin America) during the two months prior to study enrolment, * Food restrictions such as vegan, vegetarian, ketogenic, low carb, paleo, raw diets, caloric restrictive diets, * Artificially sweetened beverage intake \>1000 ml/ per day, * Female participants will be excluded if they are pregnant, have given birth in the last 6 months, or are lactating, * Subject having a hierarchical or family link with the research team members, * Occurrence of fever episodes, infection, or vaccination during 14 days before the start of the study.