Vitamin D status in chronic fatigue syndrome/myalgic encephalomyelitis: a cohort study from the North-West of England.
Earl, Kate E, Sakellariou, Giorgos K, Sinclair, Melanie et al. · BMJ open · 2017 · DOI
Quick Summary
This study investigated whether low vitamin D levels contribute to the fatigue experienced by people with ME/CFS. Researchers compared 92 ME/CFS patients with 94 healthy controls and found that ME/CFS patients actually had higher vitamin D levels, often because they were taking vitamin D supplements. Importantly, there was no connection between vitamin D levels and how fatigued patients felt, suggesting that vitamin D deficiency is not a cause of ME/CFS fatigue.
Why It Matters
Since severe vitamin D deficiency is known to cause muscle fatigue and myopathy, this study addresses an important question about whether correcting vitamin D status could improve ME/CFS symptoms. The findings suggest that vitamin D supplementation alone is unlikely to resolve fatigue in ME/CFS patients, helping redirect research and clinical efforts toward other potential biological mechanisms.
Observed Findings
ME/CFS patients had significantly higher serum total 25(OH)D compared to healthy controls (60.2 vs 47.3 nmol/L, p=0.001).
The higher vitamin D levels in ME/CFS patients were associated with increased vitamin D supplement use rather than higher dietary intake.
No significant association was found between vitamin D levels and fatigue severity measured by the Chalder Fatigue Questionnaire.
No evidence of vitamin D deficiency (defined as 25(OH)D<25 nmol/L) was present in the ME/CFS group.
Inferred Conclusions
Low serum 25(OH)D concentrations are not a contributing factor to fatigue in ME/CFS.
Vitamin D supplementation is unlikely to be an effective treatment for ME/CFS-related fatigue, at least in patients with adequate baseline vitamin D status.
Other biological mechanisms beyond vitamin D status should be investigated as potential causes of ME/CFS fatigue.
Remaining Questions
Would vitamin D supplementation benefit the small subset of ME/CFS patients with baseline deficiency, or is fatigue truly independent of vitamin D status across all levels?
Do tissue-level vitamin D concentrations or vitamin D receptor function differ in ME/CFS, despite normal circulating levels?
Could vitamin D play a role in other ME/CFS symptoms besides fatigue, such as immune dysfunction or post-exertional malaise?
What This Study Does Not Prove
This study does not prove that vitamin D plays no role in ME/CFS; it only shows that baseline deficiency is not a primary contributor to fatigue severity in this cohort. The cross-sectional design cannot determine causality or whether vitamin D supplementation might help a subset of patients with very low baseline levels. The study also does not address other forms of vitamin D metabolism or tissue-level vitamin D status.