19/02/2026
Managing comorbidities in ME/CFS is useful in reducing overall symptom burden for affected individuals.
But what about vitamin D supplementation?
Vitamin D deficiency is common in general and even more common amongst individuals with ME/CFS it would seem. This is not a surprise as vitamin D is sometimes referred to as the "sunshine vitamin" as it is produced by the body when skin is exposed to direct sunlight outdoors (and individuals with ME/CFS often spend more time indoors than others).
A group of researchers from Japan conducted a randomised controlled trial evaluating the efficacy of vitamin D replacement therapy guidance in 91 participants with ME/CFS following SARS-CoV-2 (COVID-19) infection or vaccination and co-existing vitamin D insufficiency or deficiency. At first glance, the results may be unintentionally interpreted as suggesting Vitamin D supplementation is helpful in ME/CFS. On second glance, the findings (which need to be approached with caution) seem to actually suggest the opposite - Vitamin D supplementation alone does not have much of an effect on ME/CFS symptoms.
Read a breakdown of the study: https://tinyurl.com/2r7jsrbs
Important note:
It is important to consult a healthcare professional to determine whether supplementation is needed and, if so, the appropriate dosage to address any nutrient deficiency, including vitamin D.
Although a study may show minimal or mixed effects of vitamin D supplementation on ME/CFS symptoms, vitamin D remains an essential nutrient involved in key physiological processes such as bone health, immune function, and muscle function. The NHS provides detailed information on Vitamin D on its website. https://tinyurl.com/mwtnpx95