The effect of probiotic and synbiotic supplementation on sleep parameters in exercised population: a systematic review and synthesis without meta-analysis (SWiM) of randomized controlled trials

Clinical Snapshot

Key Findings

• P Value: Combined probiotics p < 0.01, synbiotics p < 0.001

• Effect Size: Nine of twelve primary outcomes favored supplementation

• Primary Outcome: Sleep parameters (quality and latency)

• Nnt Or Sensitivity: Not calculable from available data

• Confidence Interval: Not reported in abstract

Clinical Application

Moderate - supplements readily available but require standardized protocols and monitoring Relevant to Australian sports medicine practice; probiotics available through TGA-approved supplements; aligns with Sports Medicine Australia guidelines for athlete recovery Athletes and exercised individuals across multiple sports requiring sleep optimization

Abstract

BACKGROUND: Sleep is crucial for recovery and optimal performance in athletes; however, poor sleep is common during periods of intensive training or competition. The microbiota-gut-brain axis suggests probiotics and synbiotics could modulate sleep, but evidence in exercised populations is limited. OBJECTIVE: To systematically review randomized controlled trials (RCTs) assessing the effects of probiotic and synbiotic supplementation on sleep in exercised populations, using a Synthesis Without Meta-analysis (SWiM) approach. METHODS: PubMed, Scopus, Web of Science, and ProQuest were searched up to September 2025. Eligible studies were RCTs including exercised individuals, testing probiotics or synbiotics, and reporting sleep outcomes. Data extraction, risk of bias assessment (RoB 2), and narrative synthesis followed SWiM guidelines. RESULTS: Six RCTs (n = 180) were included: four probiotic and two synbiotic interventions lasting 4-17 weeks. Populations included athletes from multiple sports across four continents. Nine of twelve primary sleep outcomes favored supplementation, with significant effects for probiotics (combined p < 0.01) and synbiotics (p < 0.001). Benefits were most consistent for subjective sleep quality and, in some cases, sleep latency. Secondary outcomes showed occasional reductions in stress, anxiety, and fatigue. CONCLUSION: Probiotic and synbiotic supplementation may improve sleep in exercised populations, especially perceived quality and latency. Evidence supports cautious, adjunctive use, but larger, standardized trials are needed to confirm effects.PROSPERO registration number: CRD420251151264.

References

1. 1.Salehi Asl, M., Ahmadi, F., Ershadmanesh, M., Mortezapour, E., Torki, F., Danandeh, A., Dehghani, E., & Danandeh, K. (2026). The effect of probiotic and synbiotic supplementation on sleep parameters in exercised population: a systematic review and synthesis without meta-analysis (SWiM) of randomized controlled trials. Journal of the International Society of Sports Nutrition. https://doi.org/10.1080/15502783.2026.2670564