Free and Bioavailable Vitamin D Are Correlated with Disease Severity in Acute Pancreatitis: A Single-Center, Prospective Study

Acute pancreatitis (AP) is primarily caused by inflammation and immunological responses, both of which are regulated by vitamin D. The purpose of this study was to examine the correlation between the severity of AP and vitamin D levels, including its total, free, and bioavailable forms. Eighty individuals with AP were enrolled in this study. Serum levels of free 25(OH)D₃, bioavailable 25(OH)D₃, and total 25-hydroxyvitamin D 25(OH)D₃ were assessed. The severity of the disease course was assessed by scoring systems (Revised Atlanta classification, Ranson score, CTSI). Vitamin D deficiency was common in AP patients, with 31.3% being categorized as deficient (<50 nmol/L) and 27.5% having a severe deficiency (<30 nmol/L). Compared to patients with adequate vitamin D status, those with lower vitamin D levels had a significantly higher risk of developing moderate-to-severe AP (44.7% vs. 14.3%, <i>p</i> = 0.029). Patients with severe vitamin D insufficiency were the only ones who experienced severe AP. Clinical outcomes showed similar correlations: patients with significant vitamin D deficiency had longer hospital stays (mean of 12.1 ± 5.3 days vs. 7.8 ± 3.4 days, <i>p</i> = 0.018) and higher rates of ICU admission (31.8% vs. 8.0%, <i>p</i> = 0.007). Low levels of total, free, and bioavailable vitamin D were significantly associated with the severity of AP and ICU admission. Free, bioavailable, and total vitamin D were correlated with the severity of acute pancreatitis. All severe cases occurred in patients with severe vitamin D deficiency. Given the observational design, these associations require confirmation in interventional or mechanistic studies.