Kodama, Shinichiro, Nakata, Mitsuko, Konishi, Nafuko et al. · Nutrients · 2026 · DOI
This study tested whether vitamin D supplementation could help people with ME/CFS who developed the condition after COVID-19 vaccination or infection and had low vitamin D levels. Half the participants received vitamin D supplements plus guidance on diet and sun exposure, while the other half received only the supplement. The group that received full guidance had significantly more symptom improvement, with 16 people improving enough to no longer meet ME/CFS diagnostic criteria compared to just 1 person in the other group.
ME/CFS affecting post-COVID and post-vaccination populations represents a growing clinical burden with limited evidence-based treatments. This study provides the first RCT evidence that targeted vitamin D replacement may significantly improve ME/CFS symptoms in the subset of patients with documented deficiency, potentially offering an accessible, low-risk intervention for a subset of affected individuals.
This study does not establish that vitamin D deficiency causes ME/CFS; it only demonstrates that correcting deficiency in those who already have ME/CFS can improve symptoms. The open-label design introduces potential bias, and the intervention combined multiple elements (supplementation plus lifestyle counseling), so the independent contribution of vitamin D versus diet/exercise cannot be isolated. Results apply only to patients with confirmed vitamin D insufficiency/deficiency and may not generalize to ME/CFS patients with normal vitamin D levels.
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
Kodama, Shinichiro, Nakata, Mitsuko, Konishi, Nafuko, Yoshino, Masato, Fujisawa, Akinori, Naganuma, Mutsuo, et al. (2026). Vitamin D in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome After COVID-19 or Vaccination: A Randomized Controlled Trial.. Nutrients. https://doi.org/10.3390/nu18030521
BibTeX
@article{mecfsatlas-kodama-2026-vitamin-myalgic,
author = {Kodama, Shinichiro and Nakata, Mitsuko and Konishi, Nafuko and Yoshino, Masato and Fujisawa, Akinori and Naganuma, Mutsuo and Kobayashi, Yuki and Hirai, Yuriko and Kitagawa, Akiko and Miyokawa, Mariko and Mishima, Ryo and Teramukai, Satoshi and Fukushima, Masanori},
title = {Vitamin D in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome After COVID-19 or Vaccination: A Randomized Controlled Trial.},
journal = {Nutrients},
year = {2026},
doi = {10.3390/nu18030521},
note = {PubMed: 41683343},
url = {https://www.mecfsatlas.com/evidence/kodama-2026-vitamin-myalgic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/kodama-2026-vitamin-myalgic
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