Comparison of the efficacy of daily versus weekly vitamin D supplementation on GOLD classification in COPD patients with vitamin D deficiency: An open-label randomized clinical trial

Background Chronic obstructive pulmonary disease (COPD), characterized by irreversible airflow limitation, markedly reduces expiratory airflow. COPD patients commonly suffer from vitamin D deficiency, which is strongly associated with reduced forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Aim This study compared the effects of weekly versus daily vitamin D supplementation on lung function in COPD patients with low baseline vitamin D levels. Methods In this open-label randomized clinical trial, 49 patients with COPD and baseline serum 25-hydroxyvitamin D levels below 30 ng/mL were allocated to receive either daily 4000 IU or weekly 50,000 IU vitamin D3, in addition to standard COPD treatment, for 12 weeks. Summary After the intervention, serum vitamin D levels increased in both supplementation groups, while lung-function measures also increased from baseline. Although the weekly group showed numerically higher post-intervention FEV1 and FEV1 percentage values, the between-group differences were not statistically significant after adjustment for baseline age ( p = 0.079 for absolute FEV1; p = 0.981 for FEV1 percentage). We observed a significant association between post-intervention vitamin D levels and post-intervention FEV1 ( R 2 = 0.42, p < 0.001). These findings do not demonstrate superiority of the weekly regimen over the daily regimen, and larger randomized controlled trials are needed to determine whether clinically meaningful differences exist between dosing schedules.