title: Burning daylight: balancing vitamin D requirements with sensible sun exposure.
abstract: OBJECTIVE
  To examine the feasibility of balancing sunlight exposure to meet vitamin D requirements with sun protection guidelines.
  
  
  METHODS
  We used standard erythemal dose and Ultraviolet Index (UVI) data for 1 June 1996 to 30 December 2005 for seven Australian cities to estimate duration of sun exposure required for fair-skinned individuals to synthesise 1000 IU (25 µg) of vitamin D, with 11% and 17% body exposure, for each season and hour of the day. Periods were classified according to whether the UVI was < 3 or ≥ 3 (when sun protection measures are recommended), and whether required duration of exposure was ≤ 30 min, 31-60 min, or > 60 min.
  
  
  METHODS
  Duration of sunlight exposure required to achieve 1000 IU of vitamin D synthesis.
  
  
  RESULTS
  Duration of sunlight exposure required to synthesise 1000 IU of vitamin D varied by time of day, season and city. Although peak UVI periods are typically promoted as between 10 am and 3 pm, UVI was often ≥ 3 before 10 am or after 3 pm. When the UVI was < 3, there were few opportunities to synthesise 1000 IU of vitamin D within 30 min, with either 11% or 17% body exposure.
  
  
  CONCLUSIONS
  There is a delicate line between balancing the beneficial effects of sunlight exposure while avoiding its damaging effects. Physiological and geographical factors may reduce vitamin D synthesis, and supplementation may be necessary to achieve adequate vitamin D status for individuals at risk of deficiency.
authors.affiliation: Westmead Breast Cancer Institute, University of Sydney, Sydney, NSW, Australia. Kellie.Bilinski@bci.org.au
authors.forename: Kellie L
authors.initials: KL
authors.lastname: Stalgis-Bilinski
authors.forename: John
authors.initials: J
authors.lastname: Boyages
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Salisbury
authors.forename: Colin R
authors.initials: CR
authors.lastname: Dunstan
authors.forename: Stuart I
authors.initials: SI
authors.lastname: Henderson
authors.forename: Peter L
authors.initials: PL
authors.lastname: Talbot
mesh_terms: D001315:Australia; D004307:Dose-Response Relationship, Radiation; D019983:Guideline Adherence; D006291:Health Policy; D006370:Heliotherapy / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D012621:Seasons; D012880:Skin Pigmentation; D013472:Sunlight / Q000009:adverse effects*; D013997:Time Factors; D014807:Vitamin D / Q000096:biosynthesis*; D014808:Vitamin D Deficiency / Q000517:prevention & control*
chemical_list: D014807:Vitamin D