The aim of this study is to evaluate the bifidogenic effect and other potentially beneficial effects on the microbiome of GOS.

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.