title: Layer Thickness of SPF 30 Sunscreen and Formation of Pre-vitamin D.
abstract: BACKGROUND
  Most studies have demonstrated that sunscreens with lower sun protection factor (SPF) do not prevent the production of vitamin D because much lower amount of sunscreen (SPF<30) is applied than recommended (2 mg/cm(2)) indicating that a significant amount of UV radiation can penetrate the skin. Since less sunscreen is applied, higher SPF sunscreens may be used to achieve the desired protection. However, there is little information regarding the application of high-SPF sunscreen and vitamin D formation. The aim of this study was to measure the influence of the amount of two SPF 30 sunscreens on pre-vitamin D formation in a cuvette with 7-dehydrocholesterol.
  
  
  RESULTS
  Sunscreen with physical (reflecting) or chemical (absorbing) UV filters exhibits different levels of protection in vitro even if the SPF is the same. The level of photoprotection is differentially reduced when less sunscreen than the recommended application thickness is applied.
  
  
  CONCLUSIONS
  The usual application of 0.8-1 mg/cm(2) is below the recommended value of 2 mg/cm(2), and pre-vitamin D may be formed when lower amounts of SPF ≤30 sunscreen are applied, showing that a significant amount of UV radiation may enter the skin.
authors.affiliation: Department of Radiation Biology, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, Oslo, Norway.
authors.forename: Mantas
authors.initials: M
authors.lastname: Grigalavicius
authors.affiliation: Department of Radiation Biology, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, Oslo, Norway.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Iani
authors.affiliation: Department of Radiation Biology, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, Oslo, Norway astaj@rr-research.no.
authors.forename: Asta
authors.initials: A
authors.lastname: Juzeniene
mesh_terms: D003684:Dehydrocholesterols / Q000378:metabolism*; D006801:Humans; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D013472:Sunlight; D013473:Sunscreening Agents / Q000008:administration & dosage*; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D003684:Dehydrocholesterols; D013473:Sunscreening Agents; D014807:Vitamin D; C016705:7-dehydrocholesterol
keywords: 7-dehydrocholesterol; Sunscreen; skin protection; solar ultraviolet radiation; vitamin D