Possible Interaction: Caffeine and Theanine

“ Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine–caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005).”

“ Theanine and caffeine seem to have additive effects on attention in high doses.”

“Thus, under emotional arousal, caffeine and theanine exert opposite effects on certain attentional processes, but when consumed together, they counteract the effects of each other.”

“ Caffeine has a strong antagonistic effect against theanine.”

“ L-theanine and caffeine combined were found to particularly improve performance in attention-switching tasks and alertness, but to a lesser extent than caffeine alone.”

“Moreover, L-theanine was found to lead to relaxation by reducing caffeine induced arousal.”

“ l-Theanine– caffeine combination improved total cognition composite (p = 0.041), d-prime in the Go/NoGo task (p = 0.033) and showed a trend of improvement of inhibitory control (p = 0.080).”

“ l-Theanine– caffeine combination was associated with decreased task-related reactivity of a brain network associated with mind wandering (i.e. default mode network).”

“Factorial analysis suggested that l-theanine and caffeine seem to have a synergistic action in decreasing mind wandering.”

“However, the effect of theanine was blocked by caffeine and gallate-type catechins, which are the main components in tea.”

“This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine , whereas separate administration of either substance was found to have a lesser impact.”

“ Caffeine , one of the main components in green tea, can interfere with sleep and block the effect of theanine.”

“ConclusionsCombining 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.”

“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.”