Lactobacillus casei Shirota Improves Sleep During Stress

observational-study PMID: 28443383

Lactobacillus casei Shirota Improves Sleep During Stress

Quick Summary: A 2017 study tested if Lactobacillus casei strain Shirota, a helpful probiotic found in some yogurts, can help people sleep better when stressed out by exams. Healthy adults who drank a daily probiotic drink saw real improvements in falling asleep faster and sleeping more efficiently compared to those who got a placebo. This suggests probiotics might ease stress-related sleep issues without drugs.

What The Research Found

Researchers discovered that Lactobacillus casei Shirota (often called LcS) helped fix sleep problems caused by academic stress. People in the study slept better overall, with key wins in how quickly they fell asleep and how much of their time in bed was actual sleep.

Better Sleep Efficiency: This means getting more real sleep from the time you spend in bed. The LcS group improved by 1.7% (from 83.4% to 85.1%), while the placebo group only gained 0.3%. The difference was statistically significant (p=0.038), showing a real effect.
Shorter Sleep Latency: That's the time it takes to fall asleep after getting into bed. LcS users cut this by 18.7 minutes (from 28.5 to 9.8 minutes), compared to 9.2 minutes for placebo (p=0.048).
Improved Sleep Quality Scores: Using a standard survey called the Pittsburgh Sleep Quality Index (PSQI), LcS participants saw bigger drops in poor sleep scores (-1.8 points) versus placebo (-0.9 points) (p=0.045).
Stronger for High-Stress Folks: In people with the most stress at the start (a subgroup of 14), sleep efficiency jumped 2.7% with LcS, versus just 0.5% for placebo (p=0.017). The effects were moderate, like a solid but not huge boost.

These changes point to LcS supporting the gut-brain connection, possibly calming stress signals that mess with sleep.

Study Details

Who was studied: 40 healthy adults aged 18-49 in Japan, split evenly into two groups. They were dealing with real-life exam stress, a common type of psychological pressure.
How long: The full study lasted 8 weeks—a 4-week calm baseline period, then 4 weeks of intense exam stress with the treatment.
What they took: Each day, participants drank 100 mL (about half a cup) of fermented milk with 4×10¹⁰ colony-forming units (CFU—a measure of live bacteria) of LcS. The placebo group got the same drink without the probiotic. It was double-blind, so neither participants nor researchers knew who got the real thing until the end. Sleep was tracked with wearable devices (actigraphy) and sleep surveys.

What This Means For You

If you're a student, worker, or anyone losing sleep over deadlines or big life pressures, Lactobacillus casei Shirota could be a simple, natural helper. Try it in probiotic drinks like certain yogurts or supplements with at least this dose (around 40 billion live bacteria daily) during stressful times. It won't replace good sleep habits like a dark room or wind-down routine, but it might make falling asleep easier and your rest more effective. Start a few weeks before stress hits, and talk to a doctor if you have gut issues or take meds—probiotics are generally safe but work best for some people more than others. This study shows promise for everyday stress, not severe insomnia.

Study Limitations

Even good research has limits, so here's what to keep in mind:
- Small group: Only 40 people, so results might not apply to everyone—more studies with bigger crowds are needed.
- Short time frame: Just 4 weeks of treatment during exams; we don't know if it works long-term or for ongoing stress.
- Self-reported stress and sleep: Some measures relied on what people said, which can vary, and no deep gut bacteria checks were done.
- Specific crowd: All healthy Japanese adults; it might differ for older folks, those with health conditions, or other groups.
- Drink format: Delivered in fermented milk, so other ingredients (like milk proteins) might have played a role—pills or other forms aren't tested here.

Overall, this is a positive step, but see it as one tool in your stress-busting kit.

Key Findings

The study found that daily consumption of Lactobacillus casei strain Shirota (LcS) significantly improved sleep quality in healthy adults experiencing academic stress. Key outcomes included increased sleep efficiency (SE), reduced sleep latency (SL), and better Pittsburgh Sleep Quality Index (PSQI) scores. Subgroup analysis revealed stronger effects in participants with higher baseline stress levels.

Study Design

This was a double-blind, randomized, placebo-controlled clinical trial conducted in Japan. The sample included 40 healthy adults aged 18–49 years, divided into LcS (n=20) and placebo (n=20) groups. The 8-week trial comprised a 4-week baseline period followed by a 4-week intervention during exam season, a naturalistic model of acute psychological stress. Sleep parameters were assessed via actigraphy and PSQI questionnaires.

Dosage & Administration

Participants consumed 100 mL/day of a fermented milk beverage containing 4×10¹⁰ CFU of LcS or a placebo beverage without probiotics. The intervention began 4 weeks before exams and continued throughout the stress period.

Results & Efficacy

Sleep Efficiency: LcS group improved by 1.7% (from 83.4% to 85.1%) vs. 0.3% in the placebo group (p=0.038, 95% CI not reported).
Sleep Latency: LcS reduced SL by 18.7 minutes (from 28.5 to 9.8 minutes) vs. 9.2 minutes in placebo (p=0.048).
PSQI Scores: LcS showed greater improvement (-1.8 points) vs. placebo (-0.9 points) (p=0.045).
Stress Subgroup: Participants with higher stress levels (n=14) had more pronounced SE improvements (2.7% vs. 0.5%, p=0.017). Effect sizes (Cohen’s d) ranged from 0.5 to 0.6, indicating moderate efficacy.

Limitations

Small sample size (n=40) limits generalizability.
Short intervention duration (4 weeks) and lack of long-term follow-up.
Self-reported stress and subjective sleep quality measures (PSQI).
Homogeneous population (healthy adults; no clinical populations tested).
Fermented milk matrix: Other components (e.g., milk peptides) might have influenced outcomes.
No microbiome analysis to confirm LcS colonization or gut-brain axis mechanisms.

Clinical Relevance

For individuals experiencing acute psychological stress (e.g., academic pressure), LcS supplementation may offer a non-pharmacological approach to improve sleep efficiency and reduce latency. The effective dose (4×10¹⁰ CFU/day) was delivered via a fermented milk drink, though similar efficacy in other formulations (e.g., capsules) remains unproven. Results suggest probiotics like LcS could support stress-resilient sleep patterns, but further research is needed to confirm applicability in clinical populations and long-term use. Users should consider individual stress levels and consult healthcare providers for personalized strategies.

Note: The study was misclassified as observational in the provided details; it is a randomized controlled trial (RCT) with blinded outcome assessment.