BACKGROUND: 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. METHODS: 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 TNF-α 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. RESULTS: Severe deficiency in 25(OH)D (