Is L-Theanine Stress Randomized Trial safe?

Updated May 2026

Quick Answer

L-Theanine Stress Randomized Trial has evidence relevant to safety, limits, and clinician-discussion contexts, but conclusions should stay close to the cited sources. One representative finding is: Evidence regarding the acute effects of caffeine (CAF), L-theanine (TEA), and their combination remains inconsistent, particularly with respect to their combined influence on physical and cognitive performance in athletic populations.

Key Takeaways

  • 01Evidence regarding the acute effects of caffeine (CAF), L-theanine (TEA), and their combination remains inconsistent, particularly with respect to their combined influence on physical and cognitive performance in athletic populations. [Tuncer SY (2026)]
  • 02Results Condition effects were found for leg strength ( p = 0.004, ηp 2 = 0.24) and back strength ( p = 0.008, ηp 2 = 0.19). [Tuncer SY (2026)]
  • 03Additionally, no significant difference was found between the conditions in aerobic endurance, maximum isometric handgrip strength, and hand-eye coordination results. [Tuncer SY (2026)]
  • 04Introduction Modern athletic performance is driven not only by physical capacity but also by rapid decision-making, attentional control, and visuomotor coordination. [Tuncer SY (2026)]
The current Migaku evidence database contains 2 reusable source documents for L-Theanine Stress Randomized Trial. This answer focuses on safety, limits, and clinician-discussion contexts. - Evidence regarding the acute effects of caffeine (CAF), L-theanine (TEA), and their combination remains inconsistent, particularly with respect to their combined influence on physical and cognitive performance in athletic populations. [Tuncer SY (2026); evidence level 2] - Results Condition effects were found for leg strength ( p = 0.004, ηp 2 = 0.24) and back strength ( p = 0.008, ηp 2 = 0.19). [Tuncer SY (2026); evidence level 2] - Additionally, no significant difference was found between the conditions in aerobic endurance, maximum isometric handgrip strength, and hand-eye coordination results. [Tuncer SY (2026); evidence level 2] - Introduction Modern athletic performance is driven not only by physical capacity but also by rapid decision-making, attentional control, and visuomotor coordination. [Tuncer SY (2026); evidence level 2] - Under normal conditions, it is sequestered in the cytoplasm by Kelch-like ECH-associated protein 1 (Keap1), which targets it for degradation []. [Cipriano Giovanni Luca (2026); evidence level 4] Evidence levels are sorting aids, not final clinical grades. Level 1 usually indicates systematic-review style evidence, level 2 indicates randomized trials or public-health guidance, and lower levels need more cautious wording. This page is educational. People with medical conditions, pregnancy, medication use, or unusual symptoms should ask a qualified clinician before changing supplements, medication, or treatment routines.

Sources

  1. Acute effects of combined and isolated caffeine and theanine supplementation on physical and cognitive performance in competitive athletes: a randomized, double-blind, placebo-controlled crossover study.
  2. Phytochemical and Fungal Bioactive Compounds in the “Brain Health Triad”: A Narrative Review on Neurostimulating, Neurotrophic, and Neuroprotective Synergy