Based on evidence from Pillser's research database, L-Theanine shows promise for improving sleep quality.

What the Research Says

According to Pillser's research database, there is 1 study (a systematic review and meta-analysis) on L-Theanine and improved sleep quality¹:

Effect Type	Count
✅ Beneficial	1 study
⚪ Neutral	0
❌ Harmful	0

Key Study Findings

A 2025 systematic review and meta-analysis (n=897 participants across 12 studies) found that L-Theanine consumption led to a statistically significant improvement in overall subjective sleep quality, with a moderate effect size (SMD = 0.43, 95% CI [0.04, 0.83], p = 0.03)².

How L-Theanine May Work

L-Theanine is an amino acid commonly found in green tea. It is thought to promote relaxation and improve sleep through several mechanisms:

• Promoting relaxation without drowsiness — It increases levels of GABA, serotonin, and dopamine, neurotransmitters that have calming effects.
• Reducing stress and anxiety — It can lower cortisol levels and promote alpha brain wave activity, which is associated with a relaxed but alert state.
• Synergistic effects — Some research suggests it may work well alongside other sleep-supportive supplements like magnesium or melatonin.

Summary

The available evidence from the meta-analysis suggests that L-Theanine is beneficial for improving subjective sleep quality. If you're considering it, typical doses used in studies range from 200–400 mg per day, taken about 30–60 minutes before bedtime.

Would you like me to help you find L-Theanine supplement products available on Pillser?

Footnotes

1. Pillser research database, L-Theanine and Improved Sleep Quality. ↩

2. "The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis" (2025), Pillser. ↩