Kaslow, J E, Rucker, L, Onishi, R · Archives of internal medicine · 1989
Researchers tested a liver extract injection containing folic acid and B12 (a treatment some doctors in Southern California were recommending for ME/CFS) against a placebo injection in 15 ME/CFS patients. Both the real treatment and placebo improved patients' symptoms and function, but there was no meaningful difference between the two groups. The strong response to placebo suggests that patients' expectations and other non-chemical factors may play a significant role in how they experience symptom improvement.
This study demonstrates the critical importance of placebo-controlled trials in ME/CFS research, as patients can show substantial improvement from non-specific factors alone. Understanding this placebo phenomenon helps patients and clinicians distinguish between treatments with true biological effects and those that appear helpful due to expectation, and guides future research design to more accurately identify effective therapies.
This study does not prove that LEFAC is completely ineffective for all patients or mechanisms—only that in this small trial, it did not demonstrate superiority over placebo. It also does not clarify which components (if any) of the liver extract might have biological activity, nor does it establish whether different patient subgroups might respond differently. The strong placebo response does not mean symptom improvements are 'not real,' but rather reflects the complexity of how the mind and body interact in symptom perception.
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
Kaslow, J E, Rucker, L, & Onishi, R (1989). Liver extract-folic acid-cyanocobalamin vs placebo for chronic fatigue syndrome.. Archives of internal medicine. https://pubmed.ncbi.nlm.nih.gov/2684076/
BibTeX
@article{mecfsatlas-kaslow-1989-liver-extract,
author = {Kaslow, J E and Rucker, L and Onishi, R},
title = {Liver extract-folic acid-cyanocobalamin vs placebo for chronic fatigue syndrome.},
journal = {Archives of internal medicine},
year = {1989},
note = {PubMed: 2684076},
url = {https://www.mecfsatlas.com/evidence/kaslow-1989-liver-extract},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/kaslow-1989-liver-extract
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