The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review.

Anas Anas Sohail,Stephanie P Fabara,Shae Datta,Mahika Khurana,Darshan P Sandesara,Urvish K Patel,Teresa Varghese,Fernando Ortiz,Arshdeep S Batth,Ahtesham Sabir

doi:10.7759/cureus.20828

Abstract

Attention-deficit hyperactivity disorder (ADHD) affects multiple cognitive domains, including impaired attention, hyperactivity, and increased impulsivity. According to the CDC, 9.4% of children between 2 and 17 years old have been diagnosed with ADHD. Neurotransmitters such as noradrenaline and dopamine have been suggested as crucial players in the pathophysiology of ADHD and are often targets of modern medication. Adenosine receptors types A1 and A2a in the brain are inhibited by caffeine: a stimulant known to augment attention by increasing cholinergic and dopaminergic transmission. The cognitive function of attention is also enhanced by the amino acid: L-theanine. The mechanism of action is that it behaves like a glutamate reuptake inhibitor while also acting in the hippocampus as a competitive low-affinity glutamate receptor antagonist. It’s also shown to have a neuroprotective effect by its action on the gamma aminobutyric acid (GABA)-A receptors. Our systematic review investigates the literature and clinical trials on the cognitive-enhancing effects of caffeine and L-theanine.

Highlights

BackgroundL-theanine is an amino acid found notably in green tea, black tea, and some mushrooms
The 2020 study from Kahathuduwa et al explored acute outcomes of L-theanine, caffeine, and their combined effects on maintained attention, control on inhibition, and general cognition in the five boys diagnosed with Attention-deficit hyperactivity disorder (ADHD) [10]
Improvements by the L-theanine-caffeine combination were shown on impairments related to ADHD, meaning it may be a potential therapeutic consideration

Summary

Introduction

L-theanine is an amino acid found notably in green tea, black tea, and some mushrooms. It is known for enhancing cognitive function, attention [1]. L-theanine has a few mechanisms of action. In the hippocampus, it is a competitive low-affinity glutamate receptor antagonist [2]. It acts on the gamma aminobutyric acid (GABA)-A receptors conferring a protective effect for neurons [3]. Its mechanism of action includes inhibition of adenosine receptors, types A1 and A2a in the brain, which increases cholinergic and dopaminergic transmissions, augmenting attention [4]

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