Abdulmohsen Alanazi, Ryan Alanzi, Abdullah Abdulaziz Abbod Abdo
Matcha and green-tea bioactives are widely promoted for stress and hormonal health, yet the evidence is fragmented across chemically dissimilar preparations (whole-leaf matcha, brewed green tea, isolated L-theanine, and concentrated epigallocatechin-3-gallate, EGCG) that are routinely treated as interchangeable. A compositional index for this problem already exists: the caffeine-plus-EGCG-to-L-theanine-plus-arginine (CE/TA) molar ratio, developed by Unno and colleagues for matcha and Japanese green-tea preparations, together with an indicative screening threshold. This review adopts that index and applies it, for the first time, as a stratification variable across a formally assembled endocrine evidence base, in order to map what is and is not established regarding cortisol, testosterone, and the testosterone-to-cortisol (T:C) ratio. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and its search extension (PRISMA-S), seven electronic sources were searched from inception to March 31, 2026, and findings were synthesized using the Synthesis Without Meta-analysis (SWiM) guideline because the studies were not sufficiently comparable for meta-analysis. Twenty-two studies were included (700 human participants; 673 endocrine-relevant), spanning randomized controlled trials, nonrandomized interventions, a cross-sectional study, animal experiments, and in vitro models. Studies were appraised with design-appropriate risk-of-bias tools and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework, and were stratified both by evidence tier and by CE/TA ratio. Lower-CE/TA preparations, particularly those around 2.0 or below, were the most consistently associated with stress-attenuating, cortisol-related responses, whereas higher-ratio and isolated-compound preparations were not. Catechin studies provided supportive but indirect evidence for testosterone preservation. Critically, no included matcha-specific human intervention measured testosterone and cortisol concurrently. GRADE certainty was low for cortisol-related and testosterone-related outcomes and very low for the integrated T:C endpoint. The contribution of this review is therefore 2-fold: the first tier-stratified application of the CE/TA index across an endocrine evidence base, and a formally documented map of the evidence gap, specifically the absence of chemically characterized trials with paired testosterone and cortisol measurement. Rather than a verdict that matcha is ineffective, these define a concrete, testable agenda for CE/TA-specified randomized trials with standardized sampling and paired endocrine endpoints. Systematic review registration: https://inplasy.com/inplasy-2026-4-0072/, identifier INPLASY202640072.