title: Solar Simulators for Healthy Vitamin D Synthesis.
abstract: OBJECTIVE
  The angular distribution of solar radiance and its spectral characteristics is required for the determination of vitamin D3 production in humans.
  
  
  METHODS
  The vitamin D3 weighted exposure can be calculated by integrating the incident solar spectral radiance over all relevant parts of the human body. A novel instrument allowing simultaneous measurements of spectral radiance from more than 100 directions has been developed. A large solar simulator for controlled experiments is described.
  
  
  RESULTS
  In summer it is relatively easy to obtain sufficient vitamin D because sun exposure times are short. In winter solstice vitamin D3 cannot be obtained with realistic clothing even if the exposure were extended to all daylight hours.
  
  
  CONCLUSIONS
  Improved and controlled experiments to determine vitamin D3 production are required to assess the positive effects of solar UV radiation and to assess its natural variability.
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany seckmeyer@muk.uni-hannover.de.
authors.forename: Gunther
authors.initials: G
authors.lastname: Seckmeyer
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schrempf
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany.
authors.forename: Ansgar
authors.initials: A
authors.lastname: Stührmann
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Niedzwiedz
mesh_terms: D002762:Cholecalciferol / Q000096:biosynthesis*; D006801:Humans; D012621:Seasons; D013472:Sunlight; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D002762:Cholecalciferol
keywords: UV imaging spectroradiometer; Vitamin D; human exposure; radiance