Understanding the Effects of Daily Tea Consumption on Attention, Sleep, and Mood, in Healthy Adults

NCT06224569 | Completed DMC

• 2 other identifiers: 67147MA-2021-02122N
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of these series of N-of-1 trials is to compare the effects of three tea interventions on cognition, mood, and sleep, in healthy adult participants. The main questions they aim to answer are:

• What are the short-term effects of, and differences between, three different black tea interventions on cognition, mood, and sleep, in individual participants?
• What are the short-term effects of, and differences between, three different green tea interventions on cognition, mood, and sleep, in individual participants?
• Are there any other lifestyle factors that influence the relationship between tea intake and cognition, mood, or sleep, and to what extent do they have an effect? Participants will be asked to drink three different tea interventions in four blocks of three weeks, where each week is assigned one tea intervention. At regular intervals three times per day, seven days per week, for the 12-week study duration, participants will be asked to complete a sleep questionnaire, mood questionnaire, personalised questionnaire (with questions pertaining to physical activity and work, for example), a tea consumption recall questionnaire, and two cognitive tasks based on attention (lasting one minute each). These questionnaires and tasks comprise one measurement point and take approximately five to six minutes to complete.

Conditions

The Focus of the Study is Healthy Volunteers

Keywords

Tea; Camellia sinensis; Cognition; Mood; Sleep; Black tea; Green tea; Theanine; Caffeine; N-of-1

Outcome Measures

Primary Outcomes (2)

• The cognitive domain 'attention' measured using mean reaction time and accuracy in the attention switching task

  Participants will be presented with consecutive pairs of semi-random (a random pair from the pre-defined groups with lagged replacement, i.e., a character in one pair cannot be present in the following pair) alphanumeric characters; each pair being displayed for one second. Each pair will consist of one letter (A, E, I, U, G, K, M, R) and one number (2, 3, 4, 5, 6, 7, 8, 9), in either font colour red or purple. One character will be to the left, and one to the right, of a central fixation cross; there is equal probability of the letter or number appearing on either side. The font colour changes every three pairs. No letter or number will appear in consecutive pairs. A response is made by pressing the spacebar or tapping the screen. The two conditions for a participant to respond are: if the font colour is red and the letter is a vowel; the font colour is purple, and the number is even. In other conditions, participants should withhold from responding. The task will last one minute.

  From enrolment to the end of the final tea intervention. This is the total study duration of 12 weeks.

• The cognitive domain 'attention' measured using mean reaction time and accuracy in the digit vigilance task

  Participants will be shown two streams of numbers, one of the pair on the left of the screen, and one on the right. The number on the right is the target digit and the number on the left is the random digit. The target digit is a random number between 1 and 9 that is constant for the duration of the test but random at every test occasion, and the random number stream displays random numbers between 1 and 9, consecutively, for 0.75 seconds each. No two consecutive random numbers are the same. Participants should respond by pressing the spacebar on a computer, or tapping the screen on a mobile phone or tablet, as quickly as possible, when the random digit matches the target digit. The task will last one minute and a total of 15 matches will be displayed.

  From enrolment to the end of the final tea intervention. This is the total study duration of 12 weeks.

Secondary Outcomes (2)

• Mood attributes measured using the Caffeine Research Visual Analogue Scale

  From enrolment to the end of the final tea intervention. This is the total study duration of 12 weeks.

• Sleep attributes measured using components of the Leeds Sleep Evaluation Questionnaire and sleep and wake times

  From enrolment to the end of the final tea intervention. This is the total study duration of 12 weeks.

Study Arms (2)

Series of n-of-1 trials administering black tea interventions

OTHER

A series of n-of-1 trials in which participants will receive 'black tea', 'caffeine-only black tea', and 'placebo black tea'.

Other: Black tea flavoured, tea drink; Other: Black tea flavoured, caffeine-only drink; Other: Black tea flavoured, placebo drink

Series of n-of-1 trials administering green tea interventions

OTHER

A series of n-of-1 trials in which participants will receive 'green tea', 'caffeine-only green tea', and 'placebo green tea'.

Other: Green tea flavoured, tea drink; Other: Green tea flavoured, caffeine-only drink; Other: Green tea flavoured, placebo drink

Interventions

Black tea flavoured, tea drink OTHER

Black tea powder containing 50.0 mg of caffeine and 11.5 mg of theanine, to be dissolved in 200 ml boiling water.

Series of n-of-1 trials administering black tea interventions

Black tea flavoured, caffeine-only drink OTHER

50.0 mg of caffeine in a black tea-like powder i.e., matched to the 'black tea' intervention for flavour and appearance, to be dissolved in 200 ml boiling water. Caffeine is the only biologically active ingredient in this intervention.

Series of n-of-1 trials administering black tea interventions

Black tea flavoured, placebo drink OTHER

A black tea-like powder i.e., matched to the 'black tea' intervention for flavour and appearance, containing no biologically active ingredients, to be dissolved in 200 ml boiling water.

Series of n-of-1 trials administering black tea interventions

Green tea flavoured, tea drink OTHER

Green tea powder containing 30.6 mg of caffeine and 11.1 mg of theanine, to be dissolved in 200 ml boiling water.

Series of n-of-1 trials administering green tea interventions

Green tea flavoured, caffeine-only drink OTHER

30.6 mg of caffeine in a green tea-like powder i.e., matched to the 'green tea' intervention for flavour and appearance, to be dissolved in 200 ml boiling water. Caffeine is the only biologically active ingredient in this intervention.

Series of n-of-1 trials administering green tea interventions

Green tea flavoured, placebo drink OTHER

A green tea-like powder i.e., matched to the 'green tea' intervention for flavour and appearance, containing no biologically active ingredients, to be dissolved in 200 ml boiling water.

Series of n-of-1 trials administering green tea interventions

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• People that speak English
• People that possess a computer, tablet, or smartphone that they can access regularly throughout any day of the week.

You may not qualify if:

• A current clinical diagnosis of Alzheimer's disease
• A current clinical diagnosis of Parkinson's disease
• A current clinical diagnosis of dementia
• A current clinical diagnosis of any other brain disease
• A current clinical diagnosis of cognitive impairment
• A current clinical diagnosis of any mood disorder
• People with any food allergies
• Pregnant or breastfeeding women.

Sponsors & Collaborators

• University of Aberdeen: lead
• Lipton Teas and Infusions: collaborator

Study Sites (1)

The Rowett Institute

Aberdeen, Aberdeenshire, AB25 2ZD, United Kingdom

Location

Study Officials

• Baukje d Roos, PhD

  The Rowett Institute

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: OTHER
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: The study will employ an N-of-1 study design in which 30 participants will be recruited and studied over 12 weeks. In each N-of-1 study, interventions will be delivered for six days at a time, with a one day washout in between each intervention, in four blocks of three weeks, such that each intervention is received once in each three-week block. Three intervention sequences for each arm were determined by randomly selecting four out of the six possible combinations of three interventions, and ordering the four combinations so that no intervention was preceded, or followed, by itself.

Study Record Dates

• First Submitted: January 16, 2024
• First Posted: January 25, 2024
• Study Start: September 2, 2023
• Primary Completion: May 17, 2025
• Study Completion: May 17, 2025
• Last Updated: May 23, 2025

Record last verified: 2025-05

Data Sharing

• IPD Sharing: Will not share

Locations

GB (1)