A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood
Dodd FL, Kennedy DO, Riby LM, Haskell-Ramsay CF
Psychopharmacology · 65 citations
Review labels
Neutral facts our review recorded about how this study was done. They describe method, never whether we like the result.
How it was studied
- Design
- Randomized controlled trial (indexed by PubMed)
- Studied in
- People
- Main outcome
- Health markers and function
Who paid for it
- Funding
- Funding not disclosed
Publication
- Published
- 2015-03-11 · Psychopharmacology (Berl) · vol. 232 · issue 14 · pp. 2563–2576
- Publisher
- Springer Science+Business Media
- Cited
- 101 citations · more than 98% of similar papers · 8.6× the field average
- Impact
- Top 10% most cited in its field
- References
- 72 works
- Access
- Open access (hybrid journal) · CC-BY
- Research areas
- Coffee research and impacts · Tea Polyphenols and Effects · Sirtuins and Resveratrol in Medicine
- Keywords
- Caffeine, Theanine, Placebo, Mood, Crossover study, Cerebral blood flow, Psychology, Pharmacology, Cognition, Anesthesia, Chemistry, Medicine, Clinical psychology, Psychiatry, Green tea, Food science
- MeSH
- humans, caffeine, glutamates, hemoglobins, oxyhemoglobins, central nervous system stimulants, spectroscopy, near-infrared, cross-over studies, double-blind method, affect, cognition, psychomotor performance, attention, reaction time, cerebrovascular circulation, vasoconstriction, adolescent, adult, female, male, hemodynamics, young adult
4 authors
From GB
- Fiona L. DoddNorthumbria University
- David Opare KENNEDYNorthumbria University
- Leigh M. RibyNorthumbria University
- Crystal F. Haskell‐Ramsay · correspondingNorthumbria University
Abstract
Rationale
Evidence suggests interactive effects of the tea components caffeine and L-theanine on behaviour, yet no data exists exploring the impact of the two on cerebral blood flow (CBF).
Objectives
The current placebo-controlled, double-blind, counterbalanced, crossover study examined the effects of caffeine and L-theanine on CBF and extended previous cognitive and mood findings by using lower doses than previous studies of a similar methodology, which more closely reflect the ratios present in tea.
Methods
Twelve habitual consumers and 12 non-habitual consumers of caffeine each received 75 mg caffeine, 50 mg L-theanine, 75 mg caffeine plus 50 mg L-theanine, and placebo in a counterbalanced order across four separate visits. CBF was measured via near-infrared spectroscopy with cognition and mood assessed at baseline and 30 min post-dose. Salivary caffeine and peripheral haemodynamics were co-monitored.
Results
Caffeine reduced oxygenated haemoglobin (oxy-Hb), increased deoxygenated haemoglobin (deoxy-Hb), improved performance on attention tasks and increased overall mood ratings. Increases in deoxy-Hb following caffeine were more pronounced in non-consumers. Some evidence for increased deoxy-Hb remained when caffeine was combined with L-theanine, but this effect was attenuated and the effects of caffeine on oxy-Hb, cognition and mood were eradicated.
Conclusions
Combining L-theanine with caffeine, at levels and ratios equivalent to one to two cups of tea, eliminated the vasoconstrictive effect and behavioural effects of caffeine. This supports previous findings of an interaction between these substances, despite a lack of effects of L-theanine in isolation. However, at the levels tested here, this did not lead to a positive impact on behaviour.
Abstract via Europe PMC. Copyright remains with the authors or publisher (CC BY).
Community trust
Loading…
How much do you trust this study's findings?
Comments
Sign in to rate, comment on or flag this study.Sign inSomething wrong here?
Flag this study if its information, labels or funding look wrong. An editor reviews every flag.
Sign in to rate, comment on or flag this study.Sign inEducational information about published research. Not medical advice, and not a recommendation to start or stop anything.