Single-dose effects of heat-treated L. gasseri CP2305 on EEG alpha activity and mental stress in healthy adults: double-blind crossover RCT
A single oral dose of heat-treated L. gasseri CP2305 postbiotic increased EEG alpha power and reduced tension-anxiety scores compared to placebo in healthy adults, but the effect window was limited to 60 minutes post-ingestion and absolute effect sizes were not reported in the available text.
Context
Postbiotics (inactivated bacterial cells) are under investigation as a safer regulatory alternative to live probiotics for mental health support via the gut-brain axis. Prior clinical work with live CP2305 suggested anxiolytic effects; this is the first trial examining the heat-treated form on objective brain oscillatory activity. The use of EEG as an objective marker adds methodological novelty to this research area.
What the study showed
EEG alpha power increased significantly more with CP2305 than placebo (direction: favors CP2305); RMSSD change from baseline was significantly greater with CP2305 (direction: favors CP2305); mental stress VAS and POMS2 tension-anxiety scores showed significantly greater improvement with CP2305 versus placebo (direction: favors CP2305); in vitro extracellular 5-HT was significantly higher under CP2305 versus control (direction: favors CP2305). The available text does not report absolute values, mean differences, 95% CIs, or effect sizes for any outcome.
How it was done
Double-blind, randomized, crossover, placebo-controlled RCT; n=28 healthy adults (20–44 years); single dose of CP2305 or placebo in two sessions; 8-channel EEG recorded from pre-ingestion to 60 min post-dose; simultaneous HRV recording; subjective assessment via VAS and POMS2; supplementary in vitro assay in RIN14B cell line. Registration: UMIN000056164.
Effect magnitude
Effect sizes, 95% confidence intervals, and absolute differences were not provided in the available text; only the direction and statistical significance are stated by the authors.
Limitations
Sample of 28 participants provides low statistical power and limits generalizability; 60-min outcome window precludes inference on sustained or clinically meaningful effects; washout period and randomization sequence not described in available text, preventing RoB 2 assessment; healthy participants without clinical stress reduce ecological validity; in vitro RIN14B data cannot support direct mechanistic inference in humans.
In clinical practice
Current evidence does not support clinical recommendation of heat-treated CP2305 for anxiety or stress management. Clinicians should await larger RCTs with validated clinical outcomes and defined treatment duration before considering this postbiotic for populations with anxiety disorders.
What is still missing
Larger RCTs with multi-week to multi-month treatment, populations with moderate-to-severe clinical stress, and full reporting of 95% CIs and effect sizes for all primary outcomes are required.