Dietary Protein Impact on Human Gut Health

Healthy male and female adult subjects (n=39) will be recruited to take part in an evaluation study to determine the amount of dietary protein intake which influences gut-protein-derived metabolites production. The subjects eligible to take part in this study will consume an isolated plant protein for 4 weeks, in each week the amount of protein supplementation will increase. The protein will be provided as a powder in opaque bags and participants will be instructed to dissolve the contained powder in liquids (as water) or on their food (e.g., yogurt, oat porridge). The baseline will consist in 4 visits, which in all visits faecal samples will be collected by themselves at their house or at hospital, using materials provided by the study staff. In one baseline visits (visit 4) in addition to the faecal sample, urinary sample will be collected by themselves, and blood samples will be collected at the hospital. After that, subjects will have the dietary intervention for four weeks and more 4 visits. For the visits with blood collection (visits 4 to 8), subjects will come to the study centre after 10 hours overnight fast. Subjects will have anthropometry measurements taken in the visits 4, 5, 6, and 7 using a Tanita® full body composition. Subjects will respond to questionnaires about their physical activity (once a week), Gastrointestinal Symptom rating scale (GSRS - once a week) and track their intestinal habits using Bristol scale (every day). Subjects' diet will be assessed using a web-based 24-hour diet recall (interviewed so the participants learn how to use the tool regardless of where they are) followed by multiple day records (3 times week).

Inclusion criteria

• Age 18-45 years
• Body mass index (BMI) 18,5-30 kg/m2
• Weight stable within the previous 3 months
• Maintenance of the usual physical activity habits during the study
• Intake of fibre between 15 and 25 g per day (evaluated by 3 food diaries or 24-hours recalls)
• Omnivores

Exclusion criteria

• Acute chronic disease, inflammatory or functional gastrointestinal diseases and any other disease or disorder that could affect the outcome of the study
• Use of a medication that may interfere the study outcome
• Eating disorder
• High protein intake (more than 15% of energy or maximum 1,2 g of protein per kg of body weight per day; evaluated by 3 food diaries or 24-hours recalls)
• Use of antibiotic medication during the last 3 months prior the first visit
• Use of antibiotic medication very early in life (e.g., asthmatic children or ear inflammation)
• Use of laxative or anti-diarrhoea medication within the past 3 months before the study
• Regular consumption of probiotic or prebiotic product for the past 6 weeks before the study
• Special diet that is considered to affect the study participation and/or study results, for example, high protein diets
• More than 5 h of moderate-vigorous exercise per week
• Pregnancy or breastfeeding
• Intolerance to dietary supplements that will be used in the study
• Smoking
• Abuse of alcohol or drugs (according to AUDIT score)