['Vitamin D deficiency has been frequently reported in advanced liver disease. However, its influence on alcoholic liver disease (ALD) has been poorly elucidated. We investigated the association of vitamin D with clinical, biological, and histological parameters and survival in ALD patients. Furthermore, we explored the effect of vitamin D treatment on ALD patient peripheral blood mononuclear cells (PBMCs), and in a murine experimental model of ALD.', 'Serum levels of 25-hydroxyvitamin D [25(OH)D] were determined in 324 Caucasian ALD patients and 201 healthy controls. In vitro experiments on vitamin D pre-treated PBMCs evaluated TNFα production by ELISA in culture supernatants. Mice were submitted to an ethanol-fed diet and some of them were orally supplemented three times per week with 1,25(OH)2D.', 'Severe deficiency in 25(OH)D (<10 ng/ml) was significantly associated with higher aspartate aminotransferase levels (p=1.00 × 10(-3)), increased hepatic venous pressure gradient (p=5.80 × 10(-6)), MELD (p=2.50 × 10(-4)), and Child-Pugh scores (p=8.50 × 10(-7)). Furthermore, in multivariable analysis, a low 25(OH)D concentration was associated with cirrhosis (OR=2.13, 95% CI=1.18-3.84, p=0.013) and mortality (HR=4.33, 95% CI=1.47-12.78, p=7.94 × 10(-3)) at one year. In addition, in vitro, 1,25(OH)2D pretreatment decreased TNFα production by stimulated PBMCs of ALD patients (p=3.00 × 10(-3)), while in vivo, it decreased hepatic TNFα expression in ethanol-fed mice (p=0.04).'] Is marked 25-hydroxyvitamin D deficiency associated with poor prognosis in patients with alcoholic liver disease?