Caffeine is one of the most widely ingested psychoactive drugs in the world. However, this central nervous system stimulant has raised concerns because of its inauspicious effects on health that come with its overconsumption. Recent scientific advancements have allowed for the theoretical regulation of these side effects through the combination of caffeine and Ltheanine, an amino acid that promotes relaxation and improves mental function. This minireview aims to extend current knowledge by synthesizing both beneficial and detrimental effects of the administration of the combination of caffeine and L-theanine to the human brain and cognition. Information was extensively reviewed, analyzed, and compiled from a sample of 50 works of literature published from 2014 to 2020 in the DLSU Library Databases, as well as referenced studies excluded from the given timeframe that contain highly relevant information that help structuralize the review. Dosage was found to be important in attaining benefits on mood and cognition such as suppressed anxiety and stress, positive mental state, neurochemically fostered changes in neurotransmitter systems, improved accuracy, improved semantic and recognition memory, and heightened mental alertness. On the other hand, Ltheanine was found to reduce arousal more than it regulates elevated emotions caused by caffeine while some literature found that induced cognitive effects were only independent for each substance. In summary, existing studies support the hypothesis that the combination benefits human mood and cognition. As such, future research may gear towards a build-up on knowledge and innovations on the topic
