Patients who are not able to eat normally for a longer time require parenteral nutrition, i.e. they receive liquids and nutrients directly into their veins. This can have many long-term side effects, including liver problems. This study will examine whether a specific lipid emulsion containing fish oil can improve liver disease in patients on parenteral nutrition. The investigators will compare changes in bilirubin and liver enzymes after 3 months in 10 patients receiving standard lipid emulsion to 10 patients receiving standard lipids + a fish-oil containing emulsion. The investigators will also assess liver histology, the kind of fat, oxidative stress and gene expression in the liver at the beginning and after 6 months of fish-oil. The investigators also want to compare the baseline values from all 20 patients to 20 healthy controls. This will help to explain how fish oil may improve liver disease in patients on parenteral nutrition.