a Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, 53115 Bonn, Germany. b German Aerospace Center (DLR), Institute of Aerospace Medicine, 51147 Cologne, Germany. c University of Texas Medical Branch, Galveston, TX 77555, USA. d Department of Clinical, Technological and Morphological Sciences, Division of Internal Medicine, University of Trieste, 34127 Trieste, Italy. e Human Health and Performance Directorate, NASA Lyndon B. Johnson Space Center, Houston, TX 77058, USA.