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Supplement

Tea (Camellia sinensis)

Tea comes from the leaves of the Camellia sinensis plant and supplies caffeine and l-theanine, compounds that influence alertness and calm. People mostly look at it for sharper thinking, and the evidence is strongest for reaction time, which got quicker in one study of 88 people. Attention also improved, though the evidence is moderate and the effect was small, and the studies involved healthy participants.

Sources: PMID 40314930

Best evidence
Grade A
Conditions studied
1
Outcomes
2
Graded outcomes
1100

Evidence by condition

  • Strong
  • Moderate
  • Limited
  • Very limited

1 condition

Cognitive Improvement

Cognitive Improvement: outcomes studied for Tea (Camellia sinensis)
GradeOutcomeEffectSizeStudiesPeopleStudies list
Reaction Time

Moderate Improvement

Improves (the measure goes up)Moderate effect1 study88 people

Studies that measured reaction time

Attention

Small Improvement

Improves (the measure goes up)Small effect4 people

Key findings

  • Reaction TimeCognitive ImprovementImproves (the measure goes up)
  • AttentionCognitive ImprovementImproves (the measure goes up)

Studies cited

1 study from PubMed

  1. Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.Nutr Rev · PMID 40314930