Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis
Camfield DA
Published in Nutrition Reviews
Methodology
Systematic review and meta-analysis of randomised, placebo-controlled acute-dosing human studies of L-theanine, caffeine and EGCG (alone and in combination) with cognitive and mood outcomes.
Key Findings
Meta-analysis of 49 acute-dosing studies found caffeine (typically 40-100 mg) reliably improved attention and alertness, L-theanine alone had modest effects on relaxation and attention, and the L-theanine + caffeine combination improved attention-switching accuracy and alertness more than either alone; EGCG showed no consistent acute cognitive effect but altered self-reported calmness.
Conclusions
Moderate effect sizes favour combined caffeine and L-theanine for alertness and attention in the first 2 hours post-dose.
Limitations
Acute single-dose studies only, so no conclusions about chronic tea consumption; heterogeneous cognitive test batteries and doses; many small samples in healthy young adults; several included trials industry funded; publication bias not fully excluded.
Supplements Studied
Evidence of moderate effect sizes in favor of combined caffeine and L-theanine in the first 2 hours postdose were found for outcome measures Bond-Lader alertness, attentional switching accuracy.
Outcomes Measured
Meta-analysis of 49 acute-dosing studies found caffeine (typically 40-100 mg) reliably improved attention and alertness, L-theanine alone had modest effects on relaxation and attention, and the L-theanine + caffeine combination improved attention-switching accuracy and alertness more than either alone; EGCG showed no consistent acute cognitive effect but altered self-reported calmness.
Related Health Concerns
Study Details
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Disclosures
Funding
Academic institutional funding (Swinburne University), no direct industry sponsorship declared
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