The Effects of Caffeine and L-theanine Both Alone and in Combination on Cerebral Blood Flow, Cognition and Mood

A Randomised, Double Blind, Placebo-controlled Study to Evaluate the Effects of Caffeine and L-theanine Both Alone and in Combination on Cerebral Blood Flow, Cognition and Mood.

Although the beneficial effects of caffeine on cognition and mood have been reported in a number of studies, relatively few studies have looked at the effects of caffeine in combination with other phytonutrients despite the fact that caffeine is seldom consumed in isolation. L-theanine is a naturally occurring amino-acid found in tea, and has been used historically as a relaxing agent (Haskell et al., 2008). Few have assessed the impact of l-theanine on cognition, but of those that have, the most interesting results were obtained when l-theanine was assessed in combination with caffeine (Haskell et al., 2008). It remains unclear what is underlying the reported effects.

Near Infrared Spectroscopy (NIRS) is an emerging neuroimaging technology that is capable of determining changes in cerebral blood flow (CBF) by measuring the optical properties of oxygenated and deoxygenated blood (Bunce et al., 2006). No study to date has used NIRS to assess cerebral blood flow following treatment with either caffeine, l-theanine or a combination of both. It is anticipated that the proposed study will provide some insight into the mechanism of the previously observed effects both alone and in combination.

A randomised, double-blind, placebo controlled, balanced crossover design study will assess the effects of 75mg caffeine, 50mg l-theanine and a 75mg caffeine/50mg l-theanine combination in 24 young healthy adults (18-35). Cognitive and mood assessments will take place at baseline and at 30 minutes following treatment whilst cerebral haemodynamics are measured via the technique of NIRS.

Study Overview

• Status: Completed
• Conditions: Cognitive Function; Mood
• Intervention / Treatment: Dietary supplement: Caffeine and L-theanine

• Study Type: Interventional
• Enrollment (Actual): 24
• Phase: Phase 4

Contacts and Locations

Study Locations

• United Kingdom
  • Tyne & Wear
    • Newcastle upon Tyne, Tyne & Wear, United Kingdom, NE1 8ST
      • Northumbria University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 33 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Healthy
• Aged 18-35
• Either caffeine consumers (consume more than 150mg caffeine per day) or non-consumers (less than 44mg caffeine per day).

Exclusion Criteria:

• Smoke or consume any tobacco products
• Not proficient in English language
• Pregnant (or seeking to become pregnant)
• Taking recreational, over the counter/prescription medication (including the contraceptive pill), and/or dietary/herbal supplements
• Have food allergies or sensitivities
• Have history of/current head trauma, learning difficulties , ADHD, migraines or any gastric problems

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 75mg caffeine	Dietary supplement: Caffeine and L-theanine; Acute oral administration of 75mg of caffeine, 50mg l-theanine, 75mg caffeine and 50mg l-theanine in combination or placebo. One dosage administered on each of four separate study days.; Other Names: Sun-theanine (l-theanine)
Active Comparator: 50mg l-theanine	Dietary supplement: Caffeine and L-theanine; Acute oral administration of 75mg of caffeine, 50mg l-theanine, 75mg caffeine and 50mg l-theanine in combination or placebo. One dosage administered on each of four separate study days.; Other Names: Sun-theanine (l-theanine)
Active Comparator: 75mg caffeine and 50mg l-theanine	Dietary supplement: Caffeine and L-theanine; Acute oral administration of 75mg of caffeine, 50mg l-theanine, 75mg caffeine and 50mg l-theanine in combination or placebo. One dosage administered on each of four separate study days.; Other Names: Sun-theanine (l-theanine)
Placebo Comparator: 0mg caffeine/l-theanine	Dietary supplement: Caffeine and L-theanine; Acute oral administration of 75mg of caffeine, 50mg l-theanine, 75mg caffeine and 50mg l-theanine in combination or placebo. One dosage administered on each of four separate study days.; Other Names: Sun-theanine (l-theanine)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Cerebral blood flow	0-80 minutes post dose
Cognitive function	0-70 minutes post-dose
Mood	85 minutes post dose

Collaborators and Investigators

• Sponsor: Northumbria University
• Investigators: Principal Investigator: Crystal Haskell, PhD, Northumbria University

Study record dates

Study Major Dates

• Study Start: August 1, 2009
• Primary Completion (Actual): February 1, 2010
• Study Completion (Actual): February 1, 2010

Study Registration Dates

• First Submitted: September 21, 2009
• First Submitted That Met QC Criteria: September 21, 2009
• First Posted (Estimate): September 22, 2009

Study Record Updates

• Last Update Posted (Estimate): July 23, 2010
• Last Update Submitted That Met QC Criteria: July 22, 2010
• Last Verified: July 1, 2010

More Information

Terms related to this study

• Keywords: Cognitive Function; Mood; Caffeine; Near Infrared Spectroscopy; Cerebral Blood Flow; Ltheanine
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Enzyme Inhibitors; Purinergic Antagonists; Purinergic Agents; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Antagonists; Central Nervous System Stimulants; Caffeine
• Other Study ID Numbers: 25AA1