**Acknowledgments**

The authors are most grateful to the staff at the healthcare centers, Children's Hospital and laboratories at Landspitali University Hospital, for their cooperation, the nutritionists, students and other healthcare professionals participating in data collection and last, but not least, the participating children and the families. This study was supported by Sumargjöf—The Icelandic Children's Welfare Society, the Doctoral Grants of the University of Iceland Research Fund and the Icelandic Research Fund of the Icelandic Centre for Research.
