E2 ModeratePreliminaryPEM unclearObservationalPeer-reviewedMachine draft
Effect of supplement with lactic-acid producing bacteria on fatigue and physical activity in patients with chronic fatigue syndrome.
Sullivan, Asa, Nord, Carl E, Evengård, Birgitta · Nutrition journal · 2009 · DOI
Quick Summary
This small study tested whether specific probiotic bacteria (live microorganisms that may benefit gut health) could reduce fatigue and improve physical activity in ME/CFS patients. Fifteen patients took probiotics for 4 weeks and were monitored for changes in fatigue, physical activity, and cognitive function. While some patients reported feeling better overall, the study did not find significant improvements in fatigue or activity levels, though cognitive function did improve.
Why It Matters
Understanding whether gut microbiota manipulation through probiotics can address ME/CFS symptoms is important given evidence linking dysbiosis and immune dysfunction to disease pathogenesis. Even null or modest results contribute to the evidence base and may inform design of larger, better-controlled trials.
Observed Findings
- Neurocognitive function improved during the study period
- No significant changes in fatigue severity scores during probiotic intervention
- No significant changes in physical activity scores during probiotic intervention
- Faecal microflora showed no major changes after probiotic supplementation
- 6 of 15 patients (40%) reported subjective health improvement at study end
Inferred Conclusions
- The authors conclude that improvement in health outcomes is possible in CFS patients, justifying further research.
- The authors suggest that larger, more rigorous trials of probiotics in CFS are warranted based on the modest improvements observed.
Remaining Questions
- Do probiotics provide benefit beyond placebo effect in CFS, and if so, which strains and dosages are most effective?
- Why did neurocognitive function improve while fatigue did not, and are these improvements mechanistically related?
- What characteristics predict which patients will respond to probiotic intervention?
- Are longer treatment periods or different bacterial strains more effective than those tested here?
What This Study Does Not Prove
This study does not prove that probiotics are ineffective for ME/CFS, as the small sample size and lack of control group limit statistical power and enable bias. It cannot establish causation between microbiota changes and symptom improvement, and subjective improvement in 40% of patients may reflect placebo effect rather than biological benefit.
Tags
Symptom:Fatigue
Biomarker:Cytokines
Method Flag:PEM Not DefinedNo ControlsSmall SampleExploratory Only
Metadata
- DOI
- 10.1186/1475-2891-8-4
- PMID
- 19171024
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 8 April 2026
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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