The study employs a parallel groups, randomised, placebo-controlled design in 55 (allowing for 10% attrition) adults aged 25 - 40 experiencing mild-to-moderate stress. Information sheet, consent form, screening and collection of demographic data will be conducted via Redcap at the start of the study. Each participant will then attend 3 in-person sessions at the UoR Psychology department - 1 practice session, and 2 study visits 6 weeks apart. Between the study visits, participants will be required to consume a prebiotic supplement (Bimuno®) once a day at home, and collect saliva samples on 4 occasions.
Screening (all conducted via Redcap) All participants will read through the participant information sheet and sign the consent form before completing a health and lifestyle screening questionnaire to collect demographic data and ensure they meet the eligibility criteria. If eligible, subjects will then be invited to attend an in-person practice visit.
Practice visit The practice visit will be conducted in the Nutrition, Cognition and Health lab in the Psychology department, at any time of day (within working hours) to suit the participant. During this visit, the researcher will double-check participant eligibility and talk the subject through the full trial protocol. Participants will then complete the mood questionnaires and one practice round of the cognitive task (detailed in the study visit section below). This allows participants to see the type of questions they will be asked and ensure they're comfortable answering them, as well as ensure competency on the task before collecting data in the study visits. Finally, participants will be provided with two cycles worth of saliva sample kits and a demonstration on how collect their saliva samples.
Study visit(s) Subjects will consume a standardised breakfast of one slice of white toast and butter with water at home prior to arrival (or, if the participant does not routinely eat breakfast, they may arrive for the visits fasted). Study visits will be conducted in the Nutrition, Cognition and Health lab in the Psychology department, and participants will have the option to arrive anytime between 8am and 11am. This allows participants to complete their study visits before starting their work day if necessary, but also ensures that all sessions are complete before lunch removing the need to provide standardised lunch for participants. Start time of sessions will be kept consistent across visits within participants, as will the choice to have breakfast or not. During the study visits, participants will complete the following mood and sleep questionnaires in a fixed order using Redcap.
Following the questionnaires, participants will complete two emotional cognition tasks in order to explore how the prebiotic supplement might affect emotional processing. All measures will be administered via Inquisit.
At the end of the first study visit, subjects will be provided with their intervention sachets and two more cycles-worth of saliva kits to be used at the end of the study. At the end of the second visit, participants will be given the debrief sheet and emailed a payment form to complete. Both the prebiotic and the matched placebo are supplied by Clasado Research Services Ltd, Reading UK.
