An investigation into the cognitive effects and bioavailability of components of green tea.

INTERVENTION: The investigation will employ a single centre, double‐blind, placebo controlled, five‐period crossover design with a 7‐day washout period. Participants will be required to attend one practice session followed by five testing sessions. During the practice session particpants will sign the consent form and be familiarised with the mood scales and cognitive tasks. The testing sessions will see participants taking one of four interventions: 1) Whole green tea extract standardised with regard to caffeine and catechins (‘GTE’). Extract to deliver 40 mg caffeine per dose,170 mgs catechins. 2) 40 mg synthetic caffeine (‘caffeine’) 3) Decaffeinated green tea extract (‘Decaff‐GTE’) standardised with regard to catechins. Extract to deliver 0.12 mgs caffeine; 170 mgs catechins, 4) Catechins alone i.e. without any other components of green tea extract (‘catechins’). Extract to deliver 185 mgs catechins . 5) Placebo All five treatments will be administered as capsules and will be matched for colour, smell and taste Participants will be randomly allocated to receive either treatment (1) or (2) or (3) or (4) or (5) on their first testing day. This will be done by a randomised computer number sequence generator. Over the course of the investigation, they will complete all five treatments with treatment order counterbalanced across participants. A disinterested third party will be responsible for the blinding procedure. On the testing days subjects will provide baseline blood and saliva samples then undergo baseline mood and cognitive assessment. The day’s treatment will be administered at 9.00 am +/‐ 30 min) followed exactly 30 min and 120 min later by the same mood and cognitive assessment (using parallel forms of stimuli). Final blood and saliva samples will be taken and subjects will leave the laboratory. At the end of the final visit subjects will be fully debriefed before leaving the laboratory. There will be a seven day washout period between each testing session CONDITION: Cognitive function in healthy adults. PRIMARY OUTCOME: Cognitive Performance using computerised measures aimed at evaluating attentional processes. Mood as assessed by the following questionnaires: ; ; Bond&Lader Visual analogue mood scales ; Caffeine Research Visual Analogue scales ; Stress and Fatigue Visual Analogue Mood Scales (VAMS) SECONDARY OUTCOME: Serum levels of catechins and caffeine to assess the relationship between any behavioural change and levels of active components of green tea extract. ; ; These levels will be measued by analysing venous blood collected via a vacutainer following standard phlebotomy procedures. INCLUSION CRITERIA: People who meet the following inclusion criteria will be included in the trial: 1. Male or female. 2. Aged 18‐40 years. 3. Willing and able to provide written informed consent. 4. Understands and is willing and able to comply with all study procedures. 5. Are in good general health with no history of psychiatric disease. 6. Regular caffeine consumers (between 1‐4 cups of coffee per day most days) 7. Must have corrected to normal vision