Cholecalciferol Supplementation in Strengthening Inspiratory Muscles in Cholecalciferol-Deficient Patients With Chronic Obstructive Pulmonary Disease

Inclusion Criteria: * Current or ex-smoker with at least a 10-year pack history * COPD, defined as forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) \< 70% and FEV1% predicted \< 80% * 25-hydroxy vitamin D3 (25\[OH\]D3) level less than 20 ng/mL prior to study initiation * Willingness to comply with study guidelines * Willingness to avoid alternative/additional vitamin D3 supplementation for the duration of the trial * Subject must understand the investigational nature of this study and sign an Independent Ethics Committee/Institutional Review Board approved written informed consent form prior to receiving any study related procedure Exclusion Criteria: * Personal history of lung cancer or head and neck cancer * History of malabsorption syndrome (e.g., pancreatic insufficiency, celiac disease, or tropical sprue) * History of known thyroid disease * History of known sarcoid disease * History of known abnormalities in calcium metabolism * Hypercalcemia (serum calcium in excess of laboratory upper limit normal \[ULN\]) * Self-reported consumption of more than 4 alcoholic drinks per day * Use of anti-seizure medications phenobarbital or phenytoin, which can disrupt vitamin D metabolism * History of known renal dysfunction * History of known nephrolithiasis (kidney stones) * Current use of supplemental oxygen * Inability to exercise due to musculoskeletal issue, osteoarthritis or underlying cardiac disease * Current participation in a cancer intervention prevention study, except for smoking cessation * Any condition which in the Investigator's opinion deems the subject an unsuitable candidate to receive study drug * Inability to swallow pills * Vitamin D supplementation \> 2,000 IU/day of vitamin D within 30 days prior to enrollment * Positive Pregnancy Test