The aim of this study is to develop and validate an adequate protocol of volatolome (volatile metabolites) measurement in breath of human volunteers (18-65 years) to study gut microbiome - nutrition - host interactions in a general healthy population. For this purpose, breath volatile metabolites (BVM) will be analyzed throughout test days in fasting state and after standardized meals using selected ion flow tube mass spectrometry (SIFT-MS). In addition, gut microbial functions linked notably to hydrogen/methane production, carbohydrates utilization (CAZymes), and in the production of other volatile metabolites of interest (i.e. indole, fatty acid derivatives, ...) will be unraveled through microbiome sequencing data analysis (in silico), metabolomic analyses and measurement of enzymatic activities from saliva, urine and/or fecal samples.

Inclusion Criteria:

• Woman or man, aged of 18 to 65 years;
• Body mass index (BMI) between 18 and 30 kg/m2;
• Non-smoker;
• Provision of signed and dated informed consent form;
• Stated willingness to comply with all study procedures and availability for the duration of the study;
• Speaking French.

Exclusion Criteria:

• Subject with severe systemic disease (renal or hepatic failure, cancer, pancreatic cancer, chronic pancreatitis, asthma …)
• Subject with a history or current chronic/severe gastrointestinal disorder such as duodenal ulcer, chronic colitis, or chronic inflammatory disease of the digestive tract disease (Crohn's disease, ulcerative colitis), celiac disease or irritable bowel syndrome;
• Subjects with a history of digestive tract surgery (except appendectomy);
• Subject who had surgery within the two months prior to the study
• Subjects with psychiatric problems and/or using antipsychotics
• Current or recent (< 4 weeks) intake of antibiotics, fiber supplement, and/or any products modulating gut transit (laxative, anti-diarrheal, ...) or gut microbiota composition; these products will also be avoided for the duration of the study;
• Chronic intake of drugs, except contraceptive drug;
• Subject following a low-calorie diet and followed by a doctor or dietician in progress or recently (< 6 weeks);
• Women of childbearing age who are pregnant or breastfeeding or who wish to become pregnant within the next 6 weeks or who are not using an adequate method of contraception (e.g. oral contraception, intrauterine device (IUD), abstinence, ...);
• Subjects who drink more than 3 glasses of alcohol per day (> 30 g of alcohol per day);
• Subjects having participated to another clinical trial two weeks before the screening test visit;
• Subjects who practice an intense sport activity (more than 10 hours per week of intense activity);
• Language barrier, mental or legal incapacity, unwillingness or inability to understand or not being able to participate to the study.

All data will be shared by the partners from the Consortium agreement.

• Gut and salivary microbiota composition;
• Urinary, salivary and fecal metabolites;
• Visual analogue scales data;
• Gut microbial functions;
• Nutrient intake and dietary habits;
• Well-being;
• Transit;
• Concomitant medication;
• Inclusion/exclusion criteria;
• Adverse event.

Data will be shared at the end of the study.

At the end of the study

Belonging to the project partner (Consortium agreement)