Gastrointestinal discomfort is a common condition associated with aging, low levels of physical activity, and reduced intake of fibre, water, and magnesium. Several studies have reported a positive association between the consumption of hyper-mineral water containing high levels of bicarbonate, calcium, or magnesium and improvements in gastrointestinal transit. There is evidence that magnesium and sulphate, individually, exert a laxative effect; however, the impact of other minerals remains limited.

Different mechanisms have been described to explain how the gut microbiota influences gastrointestinal transit. It is important to understand the characteristics of the gut microbiota and to determine whether the intake of hyper-mineral water, a natural source of minerals, can positively modulate it.

The aim of this randomized, placebo-controlled trial is to evaluate the effects of carbonated mineral water consumption on gastrointestinal transit and gut microbiota composition.

Inclusion Criteria:

• Age between 18 and 70 years
• History of gastrointestinal discomfort
• Not using any laxative drug for 3 days before the screening visit
• Drinking 1.0 ± 0.5 L of water per day
• Accepting and signing the informed consent

Exclusion Criteria:

• Treatment or disease (current or past) likely to interfere with evaluation of the study parameters
• Taking antibiotics in the 3 months preceding the recruitment visit
• Taking supplements or any food enriched with or containing bacteria or yeasts likely to have an effect on the gastrointestinal tract, particularly on intestinal transit, digestive comfort, gas production, or the occurrence of abdominal pain, in the 30 days preceding the recruitment visit (these products will also be banned during the study period)
• Subject having an alcohol consumption of more than 3 glasses of wine per day, or 2 glasses of beer per day, or 1 glass of hard liquor per day
• Subject having a coffee consumption greater than 5 cups per day
• Subject with constipation attributable to an organic or anatomical cause (Hirschsprung's disease, hypothyroidism, mental deficiency, psychiatric illness, neurological abnormalities, history of operation of the colon or anus, colorectal cancer, anemia, etc.)
• Subject with a history of current gastrointestinal pathology or disorder such as duodenal ulcer, chronic colitis, or chronic inflammatory disease of the gastrointestinal tract (Crohn's disease, ulcerative colitis), celiac disease, or irritable bowel syndrome
• Subject having a history of operation of the digestive tract
• Subject having undergone surgery in the two months preceding the recruitment visit
• Subject having undergone bariatric surgery
• Having participated in a weight loss program (with a 5-10% weight loss) in the last 3 months prior to the recruitment visit
• Body mass index > 35 kg/m²
• Taking supplements of magnesium, vitamins, or other minerals during the study period
• Intake of other carbonated mineral waters beyond the provided water during the study period
• Pregnancy
• Participation in another clinical trial during the last 30 days prior to the recruitment visit

Individual participant data (IPD) from this study will not be publicly shared because the ethics committee has limited their use to the approved research project. However, anonymised partial data sets or summary data may be made available upon reasonable request.