Sheedy, John R, Wettenhall, Richard E H, Scanlon, Denis et al. · In vivo (Athens, Greece) · 2009
This study found that people with ME/CFS have higher levels of specific bacteria in their gut that produce a substance called D-lactic acid. These bacteria were found in much larger quantities in stool samples from ME/CFS patients compared to healthy people. The researchers suggest this excess D-lactic acid might help explain why some ME/CFS patients experience brain fog and cognitive problems.
This research offers a potential biological explanation for the neurological and cognitive symptoms that affect many ME/CFS patients, suggesting a modifiable factor (gut microbiota composition) that could inform future interventions. Understanding whether D-lactic acid accumulation contributes to symptom severity could lead to targeted dietary or antimicrobial treatment strategies for a subset of patients.
This study demonstrates association, not causation—it does not prove that elevated D-lactic acid bacteria cause ME/CFS symptoms or dysfunction. It cannot determine whether the altered microbiota is a primary driver of disease or a secondary consequence of ME/CFS or its associated lifestyle factors. The study does not establish whether reducing these bacteria would improve patient symptoms.
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
Sheedy, John R, Wettenhall, Richard E H, Scanlon, Denis, Gooley, Paul R, Lewis, Donald P, McGregor, Neil, et al. (2009). Increased d-lactic Acid intestinal bacteria in patients with chronic fatigue syndrome.. In vivo (Athens, Greece). https://pubmed.ncbi.nlm.nih.gov/19567398/
BibTeX
@article{mecfsatlas-sheedy-2009-increased-lactic,
author = {Sheedy, John R and Wettenhall, Richard E H and Scanlon, Denis and Gooley, Paul R and Lewis, Donald P and McGregor, Neil and Stapleton, David I and Butt, Henry L and DE Meirleir, Kenny L},
title = {Increased d-lactic Acid intestinal bacteria in patients with chronic fatigue syndrome.},
journal = {In vivo (Athens, Greece)},
year = {2009},
note = {PubMed: 19567398},
url = {https://www.mecfsatlas.com/evidence/sheedy-2009-increased-lactic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/sheedy-2009-increased-lactic
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