The aim of this randomised, controlled, cross-over study is to investigate whether the intake of fermented brown seaweed can lower postprandial blood glucose levels and influence the composition of the gut microbiota in 25 healthy volunteers. Well-being and gastrointestinal symptoms as well as sensory properties of the products will also be evaluated using questionnaires.

At the screening visit, the subjects will be informed about the study procedures and inclusion/exclusion criteria will be checked. Informed consent will be signed by each subject before participating in the study. The participants will consume the active and control product, respectively, for 5 days with a 14-day wash-out period in between. Capillary blood samples will be drawn for glucose measurement at the first day of each 5-day intervention period. Faecal samples will be collected before and after each 5-day intervention period to analyse changes in gut microbial composition.

Fermented seaweed is a sustainable food with increasing interest as an ingredient of a plant-based diet. Plant-based diets are gaining popularity both because of their health benefits and low-carbon footprint. Seaweed is a rich source of minerals, polyphenols and dietary fibres like xylans, carrageenan, fucoidan, laminarin and alginate. These bioactive compounds have been shown to exert positive effects on metabolic parameters, such as blood glucose and insulin, blood lipid profile and inflammatory markers and could therefore help in the prevention of cardiovascular diseases. Besides possible health benefits, fermentation of seaweed can offer potential advantages such as improved food safety and shelf life of non-dried seaweed as well as improved sensory properties.

The project aims to investigate the effects of fermented brown seaweed (Alaria Esculenta, also known as winged kelp) on glucose metabolism and its prebiotic potential in humans. A short-term pilot study (5-day intake period) will be conducted in young healthy subjects.

Twenty-five healthy subjects will be recruited to this study. This study will be a randomised controlled cross-over study where all participants will consume the test product and the control product for 5 days. In between each 5-day intervention period, there will be a wash-out period of 2 weeks.

At the first day of each 5-day intake period, the subjects have to come to the study centre in the morning in a fasting state. A test meal with the active product or control product containing each 50g of total carbohydrates will be served. Blood samples (finger-pricking) will be taken at fasting state (0 min) and at 15, 30, 45, 60, 90, 120, 150 and 180 min. The participants will then consume the product daily for 5 days at a dose of 2x 15g baobab with or without (control) 15% of the fermented seaweed. The product will be available as a spread in packages of 15g. After a wash-out period of 2 weeks, the participants will take the other product (cross-over design).

Faecal samples will be collected before and at the end of each 5-day intervention period. The questionnaire about well-being and gastrointestinal symptoms will be filled at home daily during each 5-day intervention. Also, a sensory questionnaire will be filled in at day 1 and 5 of intervention period.

Inclusion Criteria:

• Healthy males and females
• Age 20-40 years, at the time of signing the informed consent
• BMI 20-25 kg/m2
• Stable body weight (less than 5% difference during the last 3 months)
• Willing and able to give written informed consent for participating the study
• Willing to comply with all study procedures

Exclusion Criteria:

• Intake of antibiotics within 4 weeks prior to the start of the study
• Regular intake of probiotics and/or prebiotics within 4 weeks prior to the start of the study
• Tobacco use (smoking and/or snus)
• High alcohol intake: > 4 glasses daily
• Pregnancy or lactating
• Chronical disease (e.g., liver, kidney)
• Diabetes
• Gastrointestinal disease (ulcerative colitis, Crohn's disease, irritable bowel syndrome)
• Heart disease (within the last 12 months)
• Inflammatory disease (e.g. asthma, GI inflammatory diseases) and auto-immune disease
• Treatment with corticosteroids of significant degree
• Psychological disease of significant degree
• Cancer of significant difference
• Gastric-bypass operation
• Operation planned during the study period
• Known gluten intolerance and/or lactose intolerance
• Having allergies to the food components of the study, mustard and seafoods
• Known gluten intolerance, lactose intolerance, milk protein allergy or other food allergies
• Irregular diet (i.e., not eating 3 main meals daily) or special diet (e.g. vegan, low-carb high-fat, 5-2)
• Investigator considers the subject unlikely to comply with the study procedures, restrictions, and requirements