Probiotics in Wellbeing

This study will investigate whether taking a probiotic supplement every day for 12 weeks can reduce low-level inflammation and improve wellbeing in generally healthy adults. Forty adults will be randomly assigned to receive either a probiotic capsule or a placebo capsule that looks the same but does not contain probiotic bacteria. Neither the participants nor the researchers involved in the study will know which treatment each participant receives until the study is completed. Participants will attend a study visit before starting the supplement and another visit after 12 weeks, with a remote check midway through the study. Blood samples will be collected to measure markers of inflammation and stress. Stool samples will be collected to assess the gut microbiota and substances produced by gut bacteria. Urine samples will also be collected to measure metabolites, which are small molecules produced by normal processes in the body and by interactions between the body, diet and gut microbiota. Participants will also complete questionnaires about wellbeing, mood, anxiety, quality of life and memory. The main aim of the study is to determine whether the probiotic reduces a combined measure of several markers of inflammation compared with placebo. The study will also explore whether changes in inflammation are associated with changes in wellbeing and memory, and whether these effects are accompanied by changes in the gut microbiota or in metabolic profiles measured in stool and urine. The results will help researchers understand how probiotics may influence communication between the gut, immune system and brain, and will provide information to help design a larger clinical trial.

Inclusion Criteria: * Generally healthy adults * Aged 18 to 60 years * Body mass index (BMI) 18.5 to 30 kg/m² Exclusion Criteria: * Antibiotic use within the previous 3 months * Chronic gastrointestinal disorders * Chronic immune disorders * Current probiotic or prebiotic use * Current use of immunomodulatory medication * Pregnancy or lactation * Relevant allergies