Caffeine, theanine, cognition, and mood:
Results from a randomized, placebo controlled, double-blind, balanced crossover study of the cognitive and mood effects of two compounds both alone [L-theanine (250 mg), caffeine (150 mg)] and in combination (250 mg/150 mg) suggest that beverages, like tea, containing L-theanine and caffeine may have a positive effect on cognition and mood. Twenty four undergraduate students (mean age 21.3 years) took part in the study and were asked to abstain from caffeine and alcohol 12 hours prior to the study. Participants were randomised to a treatment group and received 4 different beverages (250ml drinks as previously described) plus a placebo on separate occasions 7 days apart. On each occasion the tests were carried out before taking the drink, 30 minutes after the drink and 90 minutes post-drink. Each testing session lasted approximately 30 minutes. Compared to the isolated effects of caffeine and L-theanine, the combined action resulted in improvements in visual tasks and mental fatigue ratings. In addition the combination of caffeine and L-theanine also speeded up the completion of a number of cognitive tasks. Participants also reported fewer headache symptoms and felt more alert. Overall, L-theanine with caffeine was found to increasing alertness, reducing tiredness, and reducing headaches. (16)