1. Faculty of Medicine, University of Iceland, Reykjavik, Iceland
2. Department of Gastroenterology and Hepatology, Landspitali University Hospital, Reykjavik, Iceland
3. Primary Health Care of the Capital Area, Hafnarfjordur, Iceland
4. Department of Internal Medicine & Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden