The present invention is based on the discovery that parenteral nutrition (PN) induced liver disease, e.g. fatty liver disease, can be prevented and even reversed by administration of primarily omega-3-fatty acid with PN rather than the administration of the standard intravenous lipid emulsions that contain primarily plant derived omega-6 fatty acid. Thus, the present invention provides a method for treating or preventing liver disease in a human patient obtaining nutritional support through PN. The method comprises intravenous administration of an effective amount of an omega-3-fatty acid emulsion to the patient, wherein the patient is not administered phytosterols or plant derived fatty acids, e.g. omega-6 fatty acids derived from a plant source, and wherein the administration of the omega-3-fatty acid emulsion to the patient is for a period greater than three weeks. Preferably, the administration is for a period of greater than six weeks. More preferably, the administration is for a period greater than three months.