Effect of Vitamin D3 on Self-Perceived Fatigue
A double-blind randomized placebo-controlled trial conducted by doctors at Medical Outpatients Division University Hospital Zurich finds that Vitamin D3 treatment helps with, “significantly improved fatigue in otherwise healthy persons with vitamin D deficiency.“
This was the first double-blind placebo-controlled clinical trial to investigate the efficacy of per os (oral supplementation) vitamin D3 (cholecalciferol) in treating fatigue among otherwise healthy persons with low serum 25-hydroxyvitamin D (25(OH)D) levels.
According to the study’s participants, as published at Nih.gov, “In this study, we aimed to test if a single vitamin D dose improves fatigue after 30 days among vitamin D deficient individuals who report fatigue but are otherwise healthy.”
122 patients participated in the study, with 59 receiving a 100,000 IU supervised dose of vitamin D3 while 63 received a placebo.
The abstract of the study stated its background as follows: “Vitamin D deficiency is frequent and has been associated with fatigue in uncontrolled trials.”
Vitamin D Deficiency is caused by spending too much time indoors, wearing too many clothes while outside on warm, sunny days, failure to supplement with high-quality supplements and failure to obtain adequate amounts of vitamin D3 from food and dietary sources. 
According to separate study published in Annals of Epidemiology, a study study led by Dr. Cedric Garland, on the preventive measures of vitamin D, which projected that raising the minimum year round serum 25(OH)D level to 40 – 60 ng/ml (100-150nmo/L) would prevent approximately 58,000 new cases of breast cancer and 49,000 new cases of colorectal cancer each year, and three quarters of deaths from these diseases, in the US and Canada. 
The study, which is published at the National Institutes of Health Medial Library, defined enrollment criteria as follows:
To qualify for our enrollment criteria of vitamin D deficiency at baseline, we required a 25(OH)D level below 20 μg/L, this threshold has been used according to the latest report on dietary requirements for calcium and vitamin D from the Institute of Medicine.
25(OH) vitamin D was analyzed at the time of the screening assessment in the Institute of Clinical Chemistry, University Hospital of Zurich, using an automated immunoassay (Cobas 8000 Analyser; Roche Diagnostics, Rotkreuz, Switzerland).
Additional laboratory measures included: intact PTH, calcium, phosphate, hemoglobin, ferritin, thyroid-stimulating hormone, C-reactive protein, alanine aminotransferase, alkaline phosphatase, creatinine, creatine kinase.
The criteria used for determining study participants is as follows:
Study participants with fatigue were enrolled at the Medical Outpatients Division University Hospital Zurich. Healthy individuals who suffer from fatigue were recruited by posting announcements on in-house info boards and on the intranet of the University of Zurich and the University Hospital Zurich. Healthy subjects of 20 to 50 years with a body mass index (BMI) of 18 to 25 kg/m2 were further evaluated for inclusion.
Exclusion criteria were intake of vitamin D preparations during 8 weeks prior to study enrollment, pregnancy or lactation, hypersensitivity to vitamin D, any known cardiovascular, pulmonary, renal, or hepatic disease, anemia, hyper- and hypocalcemia (corrected serum calcium levels >2.54 mmol/L or <2.09 mmol/L, respectively, the normal range given by the local laboratory), presence of muscle or bone disease, severe infection, inflammation, malignancy, known mental disorders, sleep disorders, chronic intake of concurrent medication, except oral contraceptives, known chronic kidney disease with glomerular filtration rate (CKD-EPI-estimated) <60 mL/min/1.73 m2, medication affecting physical or mental performance, participation in any other therapeutic trial within the previous month, inability to follow the procedures of the study, for example, due to language problems, psychological disorders, dementia etc., enrollment of the investigator, his/her family members, employees, and other dependent persons (Supplemental Table).
The study used vitamin D3 (cholecalciferol) in doses of 100,000 IU, administered by way of two capsules that looked identical to the placebo.
The results of the research are truly fascinating. The results showed that 100,000 IE single dose vitamin D supplements lead to a significant improvement in fatigue in the vitamin D group compared with the placebo group.
The mean age of the participants was 29 ± 6 years, 53% were women. Mean FAS decreased significantly more in the vitamin D group (−3.3 ± 5.3; 95% confidence interval [CI] for change −14.1 to 4.1) compared with placebo (−0.8 ± 5.3; 95% CI for change −9.0 to 8.7); (P = 0.01). Amelioration of fatigue was reported more frequently in vitamin D than in placebo group (42 [72%] vs. 31 [50%]; P = 0.01; odds ratio [OR] 2.63, 95% CI for OR 1.23–5.62). Among all participants, improvement in fatigue score correlated with the rise in 25(OH)D level (R = −0.22, P = 0.02).
Vitamin D treatment significantly improved fatigue in otherwise healthy persons with vitamin D deficiency.
Primary Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5207540/