Amino AcidsL-Theanine

The polyphenol/caffeine ratio determines the arousal-inducing properties of green tea ethanol extract in mice

The study found that the ratio of total phenolic content (TPC) to caffeine in green tea ethanol extract (GE) strongly correlates with arousal-inducing effects, with an R² of 0.9428. Specifically, the EGCG/caffeine ratio was closely associated with sleep duration (R² = 0.9034), and combining L-Theanine with EGCG slightly strengthened this correlation (R² = 0.9464). The extract with 58.9 mg g⁻¹ caffeine induced arousal comparable to 25 mg kg⁻¹ caffeine in mice.

Last updated: Aug 25, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score26/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. The polyphenol/caffeine ratio determines the arousal-inducing properties of the green tea ethanol extract.

observational

Kim D, Kim S, Choi G, Lee G, Song J, Oh YT, Youn JH, Cho S · Food & function (2025)

Participants: N/A
Duration: 3 hours (wakefulness monitoring) and acute sleep test
Intervention: Green tea ethanol extract (GE) with varying polyphenol/caffeine ratios, including specific extraction with 95% ethanol for 195 minutes
Outcome: Arousal-inducing effects measured via pentobarbital-induced sleep test and sleep architecture analysis (wakefulness duration)
Effect Size: R² = 0.9428 for TPC/caffeine ratio and arousal intensity; R² = 0.9034 for EGCG/caffeine ratio and sleep duration
Population: ICR mice and C57BL/6N mice

Result:

PubMed: 40245063DOI: 10.1039/d5fo00661a

Mechanism Graph

Green tea ethanol extract contains both caffeine (stimulant) and polyphenols like EGCG
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The ratio of polyphenols (especially EGCG) to caffeine modulates the net arousal effect
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L-Theanine alone does not independently affect arousal, but combined with EGCG enhances correlation with sleep duration
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Result: Higher polyphenol/caffeine ratio reduces arousal, lower ratio increases arousal

Limitations

  • ⚠Animal study (mice) limits direct translation to humans
  • ⚠Only ethanol extracts were tested; other extraction methods or compounds may yield different results

Frequently Asked Questions

Does green tea always promote arousal?▼

No, the arousal effect depends on the polyphenol/caffeine ratio; higher polyphenol content relative to caffeine can reduce arousal, potentially promoting sleep.

What is the key compound responsible for the sleep-promoting effect in green tea?▼

L-Theanine alone did not independently affect arousal, but when combined with EGCG, the total content showed a stronger correlation with sleep duration relative to caffeine.

How was the arousal effect measured in this study?▼

Arousal was measured using the pentobarbital-induced sleep test in ICR mice and sleep architecture analysis in C57BL/6N mice, assessing wakefulness duration.

Can green tea extract be used as both a stimulant and a hypnotic?▼

Yes, the study suggests that by adjusting the polyphenol/caffeine ratio, green tea extract can be optimized for either stimulant or mild hypnotic effects.

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References

  1. 1.Kim D, Kim S, Choi G, Lee G, Song J, Oh YT, Youn JH, Cho S. "The polyphenol/caffeine ratio determines the arousal-inducing properties of the green tea ethanol extract.." Food & function, 2025. PMID: 40245063 DOI: 10.1039/d5fo00661a
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.