Plasma vitamin D and cytokines in relation to exercise in patients with fibromyalgia- A 15-week strength training intervention trial

OBJECTIVES: The underlying causes of fibromyalgia are not fully understood and a link to chronic inflammation and vitamin D deficiency has been suggested. The mechanisms involved in the associations of fibromyalgia to vitamin D, biomarkers of inflammation and their relation to exercise have not been reported previously. This study aimed to investigate the effects of exercise on plasma 25-hydroxyvitamin D3 levels in patients with fibromyalgia, and further to examine the associations between biomarkers of chronic inflammation and vitamin D status. METHODS: This is a sub-study of a larger randomised controlled multi-center trial. Women with fibromyalgia (n=84) aged 20-65 years and 36 age-matched healthy controls were included. The fibromyalgia patients were randomised to resistance exercise or relaxation therapy and were examined based on physical capacity, symptoms and biomarkers including plasma 25-hydroxyvitamin D3 and cytokines. RESULTS: At baseline, participants with fibromyalgia had lower plasma 25-hydroxyvitamin D3 compared to controls, 78.0 vs. 90.6 n mol/l (p=0.041). The 25-hydroxyvitamin D3 in participants with fibromyalgia increased after the intervention (p