Evaluating the Effects of Prebiotics on Sleep, the Gut Microbiome, Cognition, Immune Function and Stress

Inclusion Criteria: * Participants must self-assess themselves as being in good health. * Have a stable sleep/wake schedule (bedtime between 9pm and 1am and wake time between 6am and 10am at least 5 nights per week) * Aged 25 to 60 years at the time of randomisation * Fluent in English * Identify as a 'poor sleeper' as defined subjectively (i.e. poor sleep quality, unrefreshing sleep) and a total score of \>5 on the Pittsburgh Sleep Quality Index (PSQI). Exclusion Criteria: * Member of own household currently participating in this trial * Evidence of current or recent sleep disorders (e.g. sleep apnoea, insomnia, circadian rhythm disorders), taking any medication which exerts sedative effects, affects the CNS and/or sleep, or be currently unwell with any illness that affects sleep (i.e. disorders of the CNS). An initial screening for sleep disorders will be conducted using the Sleep Disorders Symptom Checklist-25 (SDS-CL; Klingman et al., 2017). If a participant reports positively to any of the 25 questions in terms of being affected for three nights per week, or more, this will be followed up using a clinical interview according to the International Classification of Sleep Disorders (ICSD-3) to exclude on the basis of a sleep disorder * History of seizures or epilepsy * Shift working or have a history of shift work within the previous six months * Currently, or within the previous 8 weeks, consuming any prebiotic or probiotic products/supplements (including specifically o…