Study Title and Description
The effects of L-theanine, caffeine and their combination on cognition and mood.
Key Questions Addressed
|1||For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?|
Primary Publication Information
|Title||The effects of L-theanine, caffeine and their combination on cognition and mood.|
|Author||CF Haskell,DO Kennedy,AL Milne,KA Wesnes,AB Scholey,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Behavior - Design Details - INCLUDED Studies
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Behavior|
|What is the objective of the study (as reported by the authors)?||The current randomised, placebo controlled, double-blind, balanced crossover study investigated the cognitive and mood effects of administration of the two agents both alone [L-theanine (250 mg), caffeine (150 mg)] and in combination (250 mg/150 mg). The tasks selected included attentional tasks as well as specific semantic memory and semantic reasoning tasks, which are known to be sensitive to caffeine (e.g. Haskell et al., 2005; Warburton, 1995; Smith et al., 1994, 1999). Additional secondary memory tasks were also included, which although not typically sensitive to caffeine, have been shown to be improved by caffeine when combined in the form of guarana´ (Haskell et al., 2007). Furthermore, this extensive range of tasks also allowed a cognitive profile for L-theanine to be produced, which is essential given the lack of evidence with regards the effects of this substance.|
|Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods)||Initial screening Prior to participation in the study volunteers signed an informed consent form and completed a medical health questionnaire. All participants reported that they were in good health and free from social drugs and medication with the exception of the contraceptive pill. Habitual smokers were excluded from the study. 2.2. Participants Participants were informed that the study investigated the cognitive and mood effects of a commercially available fruit drink containing active components (one of which may be caffeine). Twenty-four participants completed the experiment (9 male and 15 female, mean age 21.3 years, S.E.M. 0.83, range 18–34 years). All were undergraduate volunteers. Participants abstained from caffeine and alcohol for a minimum of 12 h prior to the first testing session and throughout the morning until the final testing session was completed. The study was approved by the Northumbria University Division of Psychology Ethics Committee, and was carried out in accordance with the Declaration of Helsinki. 2.3. Salivary caffeine levels Saliva samples were obtained using salivettes (Sarstedt, Leicester, UK). Samples were taken immediately prior to baseline assessment in order to confirm compliance to overnight abstinence and immediately prior to both post-treatment assessments to confirm effective caffeine absorption. The saliva samples were immediately frozen at_x0003_20 8C until thawing for in-house batch analysis using the Emit system(Syva, PaloAlto,USA). This is an enzyme immunoassay intended to measure caffeine as a metabolite and is based on competition for antibody binding sites between caffeine and an enzyme labelled drug. 2.4. Assessment Mood scales employed were the Bond– Lader visual analogue scales (Bond and Lader, 1974) and the Caffeine Research Visual Analogue Scales (CRVAS) (described in Haskell et al., 2005). Treatments Participants received four drinks containing: (1) 0 mg caffeine plus 0 mg Ltheanine (placebo); (2) 150 mg of caffeine; (3) 250 mg L-theanine and (4) 150 mg caffeine plus 250 mg L-theanine on separate occasions. In each case the treatment was presented in a 250 ml modified Peach Lite Lipton Ice Tea drink. During initial preparation all tea powder (including L-theanine and caffeine) was removed from the drink and the sweetener levels adjusted to mask the bitter taste of the high dose of added caffeine so that no discernible taste difference could be detected between the drinks. The drink also contained the following: trisodium citrate; peach flavour; peach juice; malic acid; aspartame; acesulfame K and ascorbic acid. Ten minutes was allowed for drink consumption. These drinks were prepared off-site and assigned a treatment code by a disinterested third party 2.6. Procedure Each participant was required to attend a total of 5 study days that were conducted 7 days apart to ensure a sufficient wash out between conditions. Testing took place in a suite of laboratories with participants visually isolated from each other. On arrival at their first session on the first day, participants were randomly allocated to a treatment regime using a Latin square design that counterbalanced the order of treatments across the 4 active days of the study. The first day involved completion of the test battery four times in order to control for practice effects and to allow familiarisation with the test battery and procedure on subsequent visits. The practice day data were not included in any analyses. Each of the four active study days comprised three identical testing sessions. The first was a pre-dose testing session, which established baseline performance for that day, the second took place 30 min post-drink and the final session took place 90 min post-drink. Each testing session lasted approximately 30 min and comprised producing a saliva sample, completion of the CDR test battery, a sentence verification task, serial subtractions (threes and sevens) and visual analogue mood scales. 2.7. Statistics Prior to the primary statistical analysis, separate, one way, repeated measures ANOVAs of pre-dose baseline data were conducted to ascertain any chance baseline differences in performance across study days prior to the treatments. Scores on the individual task outcomes were analysed as ‘change from baseline’ using Minitab 14.0.1. A2 _x0002_ 2 _x0002_ 2 repeatedmeasuresANOVA(General LinearModel)was carried out on the ‘change frombaseline’ data, with terms fitted to the model for caffeine (present, absent), L-theanine (present, absent) and assessment (30 min, 90 min). This analysis adequately describes the main effect of caffeine across the two caffeine containing drinks, the main effect of L-theanine across the two L-theanine containing drinks, and any interaction between the two, but does not explore the effects of the individual drinks in comparison to placebo. Therefore, any measures that generated a significant main or interaction effect were further explored using Student’s paired t-tests comparing the relevant active treatment(s) to placebo. To ensure the overall Type I error protection level all testing was two-tailed. In addition, effect sizes were calculated using Cohen’s d.|
|How many outcome-specific endpoints are evaluated?||5|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||jittery|
|List additional health endpoints (separately).||mental fatigue|
|List additional health endpoints (separately)|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Subjective|
|Optional: Name of Method or short description||Mood scales employed were the Bond–Lader visual analogue scales (Bond and Lader, 1974) and the Caffeine Research Visual Analogue Scales (CRVAS) (described in Haskell et al., 2005).|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||placebo (0 mg caffeine) vs 150 mg caffeine|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||N/A|
|Provide a general description of results (as reported by the authors).||There were a number of treatment effects on the Caffeine Research Visual Analogue Scales. Due to a data capture error with 1 dataset these analyses looks at only 23 participants. 3.5.2. ‘Tired’ There was a significant main effect of caffeine on ‘tired’ ratings [F(1, 22) = 20.14, p < 0.0001]. Comparison of the caffeinated drinks to placebo showed that caffeine plus Ltheanine significantly decreased these ratings [t(22) = 3.46, p < 0.005, d = 0.8], see Fig. 3b. 3.5.3. ‘Headache’ There was also a significant main effect of caffeine on ‘headache’ ratings [F(1, 22) = 14.3, p < 0.001] and a significant caffeine _x0002_ L-theanine _x0002_ assessment interaction [F(1, 22) = 5.11, p < 0.05]. Paired t-tests revealed a significant decrease in ‘headache’ ratings following the combination [t(22) = 2.08, p < 0.05, d = 0.6] and a significant increase following L-theanine [t(22) = 2.26, p < 0.05, d = 0.6], at 90 min, see Fig. 3d. 3.5.4. ‘Mental fatigue’ There was a significant main effect of caffeine on ‘mental fatigue’ [F(1, 22) = 8.47, p < 0.01]. Comparison between drinks showed that there was a significant decrease following caffeine [t(22) = 2.83, p < 0.01, d = 0.6], and the caffeine/L theanine combination [t(22) = 2.49, p < 0.05, d = 0.7], see Fig. 3c.|
|Did the authors perform a dose-response analysis (or trend/related analysis)?||No|
|What were the authors's observations re: trend analysis?|
|What were the author's conclusions?||Caffeine alone improved speed of digit vigilance reaction time (Fig. 2b) and accuracy of Rapid Visual Information Processing (see Fig. 2c), and attenuated increases in self reported ‘mental fatigue’ ratings.|
|What were the sources of funding?||None listed|
|What conflicts of interest were reported?||N/A|
|Does the exposure (dose) need to be standardized to the SR?||No|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).|
|List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot. Characterize value as LOAEL/NOAEL, etc. if possible.||jittery - NOAEL = 150 mg/day caffeine tired - NOAEL = 150 mg/day caffeine tense - NOAEL = 150 mg/day caffeine headache - NOAEL = 150 mg/day caffeine mental fatigue - NOAEL = 150 mg/day caffeine|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||single dose No adverse effects below Nawrot levels. Tired, mental fatigue, and headache ratings were significantly improved. Jittery ratings appeared to increase (Table 2) following coffee, but no mention was made of a statistical comparison or result.|
|What is the importance of the study with respect to the adverseness of the outcome?||Important|
No baseline characteristics have been defined for this extraction form.
Results & Comparisons
No Results found.
|Arm or Total||Title||Description||Comments|
No quality dimensions were specified.
No quality rating data was found.