title: Limited exposure to ambient ultraviolet radiation and 25-hydroxyvitamin D levels: a systematic review.
abstract: 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.
authors: Dermatopharmacology, Sir Henry Wellcome Laboratories, Faculty of Medicine, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, U.K.
authors: S A
authors: SA
authors: Rice
authors: M
authors: M
authors: Carpenter
authors: A
authors: A
authors: Fityan
authors: L M
authors: LM
authors: Vearncombe
authors: M
authors: M
authors: Ardern-Jones
authors: A A
authors: AA
authors: Jackson
authors: C
authors: C
authors: Cooper
authors: J
authors: J
authors: Baird
authors: E
authors: E
authors: Healy
mesh_terms: D003020:Clothing / Q000009:adverse effects; D004651:Employment; D005260:Female; D006801:Humans; D008297:Male; D000069079:Radiation Exposure; D012621:Seasons; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000097:blood / Q000517:prevention & control*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D