The goal of this randomized clinical trial is to evaluate the effect on the microbiota and the reduction in the number and/or intensity of symptoms of gastrointestinal discomfort of consuming a probiotic or placebo for 6 weeks in adult women and men.

The main questions to answer are:

1. To study changes in the alpha diversity of the microbiota.
2. To evaluate changes in the salivary cortisol.

For this purpose, a randomized, double blind crossover study has been designed.

Target sample size is 30 subjects.

Participants will be allocated in two groups for 16 weeks (6 weeks consuming one of the products + 4 weeks wash-out period + 6 weeks consuming the other product).

• Group 1 (n=15): 6 weeks daily consumption of one probiotic capsule + 4 weeks wash-out period+ 6 weeks daily consumption of one placebo capsule.
• Group 2 (n=15): 6 weeks daily consumption of one placebo capsule + 4 weeks wash-out period+ 6 weeks daily consumption of one probiotic capsule.

Volunteers who wish to participate in the study will be interviewed by phone to verify that they meet the main inclusion criteria. Volunteers who meet the main inclusion criteria will be invited to an information and screening visit to resolve any doubts. Volunteers who agree to participate in the study will sign the informed consent and will be randomly allocated to one of the two arms of the study and will be provided with any required material.

During the intervention, volunteers will attend 4 visits distributed in two phases of 6 weeks separated by 4 weeks of wash-out period. At the beginning and at the end of each phase there will be a clinical visit. In all visits anthropometric and body composition measurements, stool and saliva samples, as well as data about dietary and physical activity will be collected.

Inclusion Criteria:

• Volunteers of both sexes aged between 18 and 65 years old.
• Volunteers with a body mass index between 18.5 and 30 kg/m2.
• Present some type of discomfort/discomfort at gastrointestinal levels without having a specific diagnosis.The gastrointestinal symptoms rating scale will be used to more objectively detect these symptoms. A score between 3 and 5 in any of the symptoms will be an inclusion criterion.
• Present a stable weight (+/- 3 kg) in the last three months prior to the start of the study.
• Subjects must be able to understand and be willing to sign the informed consent, and must comply with all study procedures and requirements.

Exclusion Criteria:

• Subjects with relevant functional or structural anomalies of the digestive system, such as malformations, angiodysplasias, active peptic ulcers, chronic inflammatory or malabsorption diseases, hiatal hernia, reflux with medication, helicobacter pylori, celiac disease and other diagnosed intolerances, etc.
• Subjects with surgical interventions with permanent consequences in the digestive system (for example, gastroduodenostomy).
• Subjects following treatments that alter gastrointestinal function, either chronically or occasionally.
• Subjects who are being treated with antibiotics (in order to participate, they do not have to have taken antibiotics during the two months prior to the baseline visit).
• Subjects with any type of cancer or undergoing treatment for it, or with less than 5 years since its eradication.
• Subjects with any liver disease (may participate with non-alcoholic fatty liver disease).
• Subjects with allergy to any component of the product under study.
• Subjects with a high alcohol intake, more than 14 units/day (women) and 20 units/day (men).
• Pregnant or breastfeeding women.
• Subjects who present some type of cognitive and/or psychological impediment.
• Subjects in whom poor collaboration is expected or with difficulties in following the study procedures.
• Subjects who work with shift changes that include nights.
• Subjects who follow any type of supplementation that interferes with the study (example: other probiotics).
• Subjects who are immersed in a significant lifestyle change.

The products (experimental and placebo), will be produced by an external producer, who will save the codes. None of the researchers involved in the study development or analyses will know the association until the end of the study.