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 affectssleep (i.e. disorders of the CNS). An initial screening for sleep disorders will beconducted 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 ofbeing affected for three nights per week, or more, this will be followed up using aclinical 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 probioticproducts/supplements (including specifically oligosaccharides)

• Participation in any other intervention research trials

• Sleeping at a location other than their usual residence more than two nights perweek during participation

• Travel across multiple time zones within the last three months or have plannedtravel across multiple time zones during the study

• Current or recent mood disturbances or Axis I disorders

• Current misuse of alcohol and/or drugs

• Current smoker

• Recent (within the last 12 weeks) infection and/or use of antibiotic medication

• Pregnant, seeking to become pregnant or lactating

• Those using (including within the last 2 weeks) proton-pump inhibitors

• Milk allergy