Daily Lactococcus cremoris YRC3780 intake for 8 weeks improves subjective sleep quality and alleviates daytime sleepiness and difficulty falling asleep in healthy Japanese adults with sleep complaints.
In a randomized, double-blind, placebo-controlled trial of 105 healthy Japanese adults with Athens Insomnia Scale (AIS) scores ≥6, daily intake of Lactococcus cremoris YRC3780 for 8 weeks significantly improved AIS scores and change from baseline compared to placebo. Significant improvements were also seen in specific AIS items for sleep induction at 4 weeks and daytime functioning at 8 weeks, as well as in subjective measures of falling asleep quickly and sleepiness while watching TV.
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Daily Lactococcus cremoris YRC3780 intake for 8 weeks improves subjective sleep quality and alleviates daytime sleepiness and difficulty falling asleep in healthy Japanese adults with sleep complaints. The current body of evidence comprises 1 study, including 1 randomized controlled trial. EvidenceHub rates the overall confidence at 44/100 (low).
The Claim
Daily Lactococcus cremoris YRC3780 intake for 8 weeks improves subjective sleep quality and alleviates daytime sleepiness and difficulty falling asleep in healthy Japanese adults with sleep complaints.
This conclusion is most relevant to: Healthy Japanese adults with sleep dissatisfaction (AIS score ≥6).
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸Lactococcus cremoris YRC3780 improves subjective sleep quality in adults with sleep dissatisfaction: A randomized double-blind placebo-controlled study. (Nutrition and health, 2026) —
How It Works
The proposed biological pathway:
- ▸YRC3780 acts on intestinal immune cells
- ▸Promotes cytokine production
- ▸Cytokines influence sleep regulation
- ▸Improved subjective sleep quality and reduced daytime sleepiness
Who Might Benefit
Evidence fit by population:
- ▸Healthy Japanese adults with sleep dissatisfaction (AIS score ≥6)
Recommended Dose
Not specified in abstract (daily intake of YRC3780)
Limitations & Caveats
Important context when interpreting this evidence:
- ▸Effect size not reported, limiting interpretation of clinical significance
- ▸Study population limited to healthy Japanese adults, may not generalize to other ethnicities or clinical insomnia populations
- ▸Subjective outcomes only; no objective sleep measures (e.g., polysomnography) were reported
Frequently Asked Questions
What is Lactococcus cremoris YRC3780?▼
It is a probiotic strain isolated from kefir, previously known as Lactococcus lactis subsp. cremoris YRC3780, that may improve sleep quality by modulating immune responses.
How long does it take to see improvements in sleep with YRC3780?▼
In this study, improvements in sleep induction were seen at 4 weeks, and overall sleep quality and daytime functioning improvements were observed after 8 weeks of daily intake.
Who was eligible for this study?▼
Healthy Japanese adults who were dissatisfied with their sleep and had an Athens Insomnia Scale score of 6 or higher, indicating at least mild sleep complaints.
What outcomes were measured in the study?▼
The study measured subjective sleep quality using the Athens Insomnia Scale and Oguri-Shirakawa-Azumi Sleep Inventory, and daytime sleepiness using the Epworth Sleepiness Scale.
References
- 1.Fujioka I, Uchida K. “Lactococcus cremoris YRC3780 improves subjective sleep quality in adults with sleep dissatisfaction: A randomized double-blind placebo-controlled study..” Nutrition and health, 2026. PMID: 42593206 DOI: 10.1177/02601060261476102