Limited exposure to ambient ultraviolet radiation and 25-hydroxyvitamin D levels: a systematic review

Br J Dermatol. 2015 Mar;172(3):652-61. doi: 10.1111/bjd.13575. Epub 2015 Feb 3.


Vitamin D can be synthesized following exposure to ultraviolet radiation (UVR), ingested in the diet or provided through oral supplementation. The medical literature frequently states that humans obtain most of their vitamin D from sunshine and that UVR exposure is essential to maintain vitamin D levels. A systematic review was conducted to determine the requirement for UVR in maintaining adequate (> 50 nmol L(-1) ) serum 25-hydroxyvitamin D [25(OH)D] levels. Studies reporting serum 25(OH)D during situations of negligible UVR exposure were sought. Forty-one studies (from a search yielding 42 698 articles) with a total of 4211 healthy adults met the inclusion criteria, providing 56 datasets from different population groups. Over 50% of subjects had > 50 nmol L(-1) 25(OH)D in 10 of 19 datasets reporting winter levels in areas with limited UVR. In addition, > 50% of subjects had adequate 25(OH)D levels in four of 12 datasets from polar regions during periods of negligible UVR, one of nine datasets documenting clothing-related minimal UVR and two of eight datasets detailing employment-related minimal UVR. The data demonstrate that many adults maintain adequate serum vitamin D levels despite negligible UVR exposure for several months. However, we acknowledge that preceding UVR exposure leading to vitamin D storage and delayed release may account for this maintenance of adequate serum vitamin D levels. There remains a need for further research on whether UVR exposure is required for longer-term maintenance of adequate vitamin D levels.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Clothing / adverse effects
  • Employment
  • Female
  • Humans
  • Male
  • Radiation Exposure
  • Seasons
  • Ultraviolet Rays*
  • Vitamin D / analogs & derivatives*
  • Vitamin D / metabolism
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / prevention & control*


  • Vitamin D
  • 25-hydroxyvitamin D