Studies about vitamin D and chronic fatigue:
High Prevalence of Hypovitaminosis D in Patients Presenting with Proximal Muscle Weakness: A Sub-Himalayan Study (2017)
Conclusion: 99 vitamin D-deficient adult patients seeking treatment for their severe muscle weakness and/or pains (myopathy) were put on a six-month high-dose vitamin D3 therapy regimen of 60,000 IU weekly for two months followed by 60,000 IU monthly for four months. 85% of the patients who finished the treatment experienced significant improvement in their muscle strength (measured by their ability to stand up from a squatting position). The study also found that the patients with lowest vitamin D levels also had the worst myopathy compared to those with higher vitamin D levels.
Effect of Vitamin D3 on Self-Perceived Fatigue: A Double-Blind Randomized Placebo-Controlled Trial (2016)
Conclusion: A study of 120 vitamin D-deficient adults complaining of fatigue were enrolled in a 4-week-long double-blind placebo-controlled trial where they were either given a single dose of 100,000 IU of vitamin D or a placebo. The vitamin D group reported experiencing significantly improved energy levels compared to the placebo group and more members of the vitamin D group reported being cured entirely of fatigue symptoms. The study also found that those who experienced the biggest increases in their vitamin D levels also experienced the biggest improvements in their fatigue symptoms.
Correlation Between Vitamin D Levels and Muscle Fatigue Risk Factors Based on Physical Activity in Healthy Older Adults (2016)
Conclusion: A study of 85 elderly people found that those with higher vitamin D levels suffered less fatigue and were more physically active than those with lower vitamin D levels.
Conclusion: A study of 200 female Iranian nurses found that the nurses with lower vitamin D levels had worse fatigue scores.
Conclusion: A 61-year-old man was seeking treatment for severe fatigue and daytime sleepiness. It was found that he had low vitamin D levels and he was subsequently put on a vitamin D supplementation program. After two weeks the patient report improved energy levels and after three months of Vitamin D supplementation he reported that his fatigue was completely cured.
Improving the Vitamin D Status of Vitamin D Deficient Adults Is Associated With Improved Mitochondrial Oxidative Function in Skeletal Muscle (2013)
Conclusion: Twelve severely vitamin D-deficient patients complaining of fatigue and myopathy were put on an experimental vitamin D3 therapy regimen, taking 20,000 IU every other day for 3 months. All patients reported an improvement in their symptoms. Despite taking what most doctors consider a very high dose of vitamin D for three months, the average vitamin D level of the group failed to rise into the optimal range.
Vitamin D Deficiency in Patients with Myasthenia Gravis and Improvement of Fatigue After Supplementation of Vitamin D3: A Pilot Study (2012)
Conclusion: Just 800 IU of vitamin D taken daily was found to be measurably effective for reducing fatigue in myasthenia gravis patients.
Conclusion: 81 sleep patients complaining of sleep problems and daytime sleepiness had their vitamin D levels tested. Among the black patients, but not whites, lower vitamin D levels were associated with worse sleep quality (measured by the Epworth Sleepiness Scale). More than half of all these patients had vitamin D deficiency.
Vitamin D Status in Patients with Musculoskeletal Pain, Fatigue and Headache: A Cross-Sectional Descriptive Study in a Multi-Ethnic General Practice in Norway (2010)
Conclusion: In a study examining 572 patients complaining of either musculoskeletal pain, headaches, or fatigue, it was found that 58% of them were vitamin D deficient.
Conclusion: A British study of 221 chronic fatigue syndrome patients found that the patients had lower vitamin D levels compared to the general British population.
Also see studies on vitamin D and