Human Milk Oligosaccharides (HMOs) are the third most abundant class of nutrients in human milk. Studies investigating the effects of dietary HMOs in infants have shown various health and developmental benefits such as the development of the early gut microbiome (by favouring colonisation of beneficial Bifidobacterium, Lactobacillus, and Bacteroides), the development of the immune system, general infant growth, protection against infectious diseases and allergies, and stimulation of cognitive development. Only a limited number of studies have been conducted in adults, showing intake of HMOs stimulates the growth of gut Bifidobacterium in healthy adults.

The current study aims to investigate the effects of a 4-week intervention with two HMOs on gut microbiome composition, immune function and gastrointestinal symptoms in healthy adults with mild to moderate gastrointestinal complaints. The study will be conducted as a partially decentralized, double-blind, randomized, placebo-controlled, parallel group design.

Inclusion Criteria:

• Age ≥ 40 and ≤ 55 years
• Male/female
• Total score of >2 on the Gastrointestinal Symptom Rating Scale (GSRS)
• Body Mass Index 18-30 kg/m2
• Stable body weight (± 5%) for at least 6 months
• Stable lifestyle and dietary habits within the 4 weeks prior and during study period
• Owns device (computer, smartphone, tablet) with access to the internet
• Adequate fluency in the English language to understand the inform consent process, study instructions and study assessments
• Sufficient vision and hearing to complete study procedures
• Willing and able to participate, follow the study procedures and to give written informed consent

Exclusion Criteria:

• History (< 6 months prior to the study) or presence of severe gastrointestinal, metabolic, immunological, psychiatric disorder, or major surgery
• Current or past (< 4 weeks) use of prescription, over-the-counter, or traditional medication, or dietary supplements with a relevant impact on GI system or on visceral motility
• Having received antibiotic treatment < 4 weeks prior to study
• Alcohol intake >1 units/day
• Currently pregnant or pregnancy in past 6 months
• Use of pro/prebiotics < 4 weeks prior to study start
• Fully vegetarian/vegan diet < 4 weeks prior to study start
• High habitual vegetable and fruit intake (> 2 servings of fruits and >2 servings of vegetables per day) < 4 weeks prior to study start
• Lactose intolerance
• Maltodextrin allergy
• Members of the research team or their immediate family members. Immediate family member is defined as spouse, parent, child, or sibling, whether biological or legally adopted