The effects of L-theanine, caffeine and their combination on cognition and mood by Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB
L-Theanine is an amino acid found naturally in tea. Despite the
common consumption of L-theanine, predominantly in combination with
caffeine in the form of tea, only one study to date has examined
the cognitive effects of this substance alone, and none have
examined its effects when combined with caffeine. The present
randomised, placebo-controlled, double-blind, balanced crossover
study investigated the acute cognitive and mood effects of
L-theanine (250 mg), and caffeine (150 mg), in isolation and in
combination. Salivary caffeine levels were co-monitored. L-Theanine
increased 'headache' ratings and decreased correct serial seven
subtractions. Caffeine led to faster digit vigilance reaction time,
improved Rapid Visual Information Processing (RVIP) accuracy and
attenuated increases in self-reported 'mental fatigue'. In addition
to improving RVIP accuracy and 'mental fatigue' ratings, the
combination also led to faster simple reaction time, faster numeric
working memory reaction time and improved sentence verification
accuracy. 'Headache' and 'tired' ratings were reduced and 'alert'
ratings increased. There was also a significant positive caffeine x
L-theanine interaction on delayed word recognition reaction time.
These results suggest that beverages containing L-theanine and
caffeine may have a different pharmacological profile to those
containing caffeine alone.
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