The liver plays a central role in the regulation of nutrition by trafficking the metabolism of nutrients, their distribution and appropriate use. Accordingly, protein-energy malnutrition is common in patients with advanced liver disease, and it is a significant prognostic factor, affecting survival, the success of liver transplantation and quality of life. Clinical guidelines for the assessment and treatment of malnutrition have been issued by International societies, suggesting that nutritional therapy should be instituted in all patients where requirements are not adequately met by diet. The supplementation of the diet with amino acids (mainly branched-chain amino acids) and trace elements may improve nutritional status, liver function and hepatic encephalopathy. Nutritional issues should be carefully considered in Liver Units treating patients with advanced cirrhosis, and long-term, carefully controlled studies are needed to better define the type of nutritional support and the amount and timing of administration.