1. Department of Epidemiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
2. School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
3. Institute for Social Medicine, Epidemiology and Health Economics, Charite University Medical Center, Berlin
4. Institute of Epidemiology and Social Medicine, University Muenster, Muenster, Germany