Effects of combined GABA and L-theanine supplementation on sleep quality: an exploratory study

Sleep disorders are a global issue, and sleep supplements and new devices for daily sleep status assessment are becoming widely available. Gamma-aminobutyric acid (GABA) and L-theanine are dietary supplements commonly used to improve sleep. In this single-arm study, we examined whether combined intake of GABA (700 mg/day) and L-theanine (200 mg/day) improves sleep in adults with sleep problems.

Participants received supplements for 4 weeks, and changes in sleep quality were measured using the Pittsburgh Sleep Quality Index (PSQI). Furthermore, sleep-related data measured using the Fitbit Charge 5 were evaluated before and after supplement intake.

We obtained results from 19 participants and found a significant improvement in the total PSQI score (mean ± standard deviation), from 9.42 ± 1.80 before to 6.26 ± 1.66 after supplement intake (mean difference, -3.15; 95% confidence interval, -4.01 to -2.31, p < 0.001). Sleep recovery scores, which are 25-point scores calculated from heart rate during sleep and at rest and the time of turning over in bed, also improved significantly (p = 0.042). Furthermore, heart rate during sleep decreased significantly (1.3 bpm decrease) in the first week of intake (p = 0.045).

Simultaneous intake of GABA and L-theanine may improve sleep in adults. As this hypothesis is based on an exploratory study, further randomized controlled trials are needed to confirm this finding.