Vitamin D is synthesized predominantly in the liver and functions as an important secosteroid hormone with pleiotropic effects. While its key regulatory role in calcium and bone homeostasis is well established, recently there is increasing recognition that vitamin D also regulates cell proliferation and differentiation, and has immunomodulatory, anti-inflammatory and anti-fibrotic properties. These non-skeletal effects are relevant in the pathogenesis and treatment of many causes of chronic liver disease. Vitamin D deficiency is frequently present in chronic liver disease and may predict non-response to antiviral therapy in chronic hepatitis C. Small studies suggest that vitamin D supplementation improves sustained viral response rates, while 1α-hydroxylase polymorphisms and vitamin D-binding protein are also implicated in therapeutic outcomes. Vitamin D deficiency also closely relates to the severity of non-alcoholic fatty liver disease (NAFLD) and is implicated in the pathogenesis of insulin resistance, a key factor in the development of NAFLD. In preclinical studies, phototherapy and vitamin D supplementation ameliorate NAFLD histopathology, while vitamin D is a powerful anti-fibrotic against thioacetamide liver injury. In liver transplant recipients severe vitamin D deficiency predicts, and vitamin D supplementation prevents, acute cellular rejection. The role of vitamin D in the activation and regulation of both innate and adaptive immune systems may explain its importance in the above liver diseases. Further prospective studies are therefore warranted to investigate the therapeutic impact of vitamin D supplementation in chronic liver disease.

Background and Aim: Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) account for a large and growing proportion of liver disease burden globally. The burden of NAFLD/NASH manifests in increasing levels of advanced liver disease and primary liver cancer in Australia. A Markov model was used to forecast NAFLD burden in Australia through 2030.Methods: A model was used to estimate fibrosis progression, primary liver cancer, and liver deaths among the Australian NAFLD population, with changes in incident NAFLD cases based on long‐term trends for changes in the prevalence of obesity. Published estimates and surveillance data were applied to build and validate the model projections, including surveillance data for the incidence of liver cancer.Results: Prevalent NAFLD cases were projected to increase 25% from the current burden (5 551 000 [4 748 000–6 306 000] cases in 2019) to 7 024 000 [5 838 000–7 886 000] cases in 2030. The projected increase in the number of NASH cases (40%) was greater than that of NAFLD cases. Incident cases of advanced liver disease are projected to increase up to 85% by 2030, and incident NAFLD liver deaths are estimated to increase 85% from 1900 (1100–3300) deaths in 2019 to 3500 (2100–6100) deaths in 2030.Conclusions: Restraining growth of the obese and diabetic populations, along with potential therapeutic options, will be essential for mitigating disease burden.