Sullivan, Asa, Nord, Carl E, Evengård, Birgitta · Nutrition journal · 2009 · DOI
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.
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.
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.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Sullivan, Asa, Nord, Carl E, & Evengård, Birgitta (2009). Effect of supplement with lactic-acid producing bacteria on fatigue and physical activity in patients with chronic fatigue syndrome.. Nutrition journal. https://doi.org/10.1186/1475-2891-8-4
BibTeX
@article{mecfsatlas-sullivan-2009-effect-supplement,
author = {Sullivan, Asa and Nord, Carl E and Evengård, Birgitta},
title = {Effect of supplement with lactic-acid producing bacteria on fatigue and physical activity in patients with chronic fatigue syndrome.},
journal = {Nutrition journal},
year = {2009},
doi = {10.1186/1475-2891-8-4},
note = {PubMed: 19171024},
url = {https://www.mecfsatlas.com/evidence/sullivan-2009-effect-supplement},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/sullivan-2009-effect-supplement
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