The risks of developing energy or nutrient deficits are of great concern in infants and children with the rare lymphoedema cholestasis syndrome 1 (LCS1)/Aagenaes syndrome. In adolescents and adults, it is not known whether LCS1 patients need specific dietary advice outside periods of cholestasis. The primary objective of the present study was to evaluate the progression of the liver disease and nutritional status in patients with LCS1 over a period of nine years. Dietary and biochemical data were obtained for patients and healthy controls in two cross-sectional studies, a baseline (2000) and a follow-up study (2009). Thirteen patients above 18 years of age with LCS1 (65%) were included (six females). Dietary intake and biochemical measures were stable in the patients from baseline until follow-up. Compared to healthy controls, the patients had significantly higher serum levels of alkaline phosphatase (p = .015 and p = .002), gamma-glutamyltransferase (p = .001 and p < .001), total bile acids (p = .037 and p = .016), and fibrinogen (p = .046 and p < .001) and lower albumin (p = .033 and p < .001) and α-tocopherol (p = .011 and p = .003) at baseline and follow-up. Despite stable liver function, the presence of a low grade of hepatobiliary dysfunction in these patients was suggested. Patients with LCS1 had a nutritional status similar to healthy controls, with no clinical deterioration of liver function during the nine-year period. The findings presented in this paper support that more than 50% of patients with LCS1 can expect a normal lifespan.