Increase in serum 25-hydroxyvitamin-D_3 in humans after solar exposure under natural conditions compared to artificial UVB exposure of hands and face

Vitamin D studies are often performed under controlled laboratory conditions and the findings may be difficult to translate to natural conditions. We aimed to determine and compare the doses of natural solar ultraviolet radiation (UVR) with doses of artificial UVB radiation of hands and face needed to increase serum 25-hydroxyvitamin-D_3 (25(OH)D). Furthermore, we aimed to investigate the natural course of 25(OH)D due to solar exposure from April to September. 46 Caucasian volunteers were included. 17 volunteers received solar UVR (Group 1) in their natural Danish environment. Individual daily solar UVR doses in standard erythema doses (SEDs) were determined with personal wristwatch UV-dosimeters. 29 volunteers (Group 2) received artificial UVB doses of 6 SEDs ( N = 14) and 3 SEDs ( N = 15) on hands and face during late-winter/early-spring when outdoor UVB is negligible. 25(OH)D-levels were determined around every second week during study periods. Solar-UVR doses and sun-exposure diaries with information of sun-exposed areas were available from 8 volunteers and used for comparison with artificial UVB doses. However no significant solar-induced Δ25(OH)D was observed when sun-exposed areas were limited to hands and face. Instead the earliest period (week 17–19) with significant Δ25(OH)D, occurring after a mean of 2 days of sun-exposing more than hands and face, was used to estimate an approximate UVR dose required to increase 25(OH)D. This estimate resulted in a dose of 4.1 solar SEDs required to increase 25(OH)D by 1 nmol l^−1. The artificial dose of 6 SEDs of only hands and face significantly increased 25(OH)D and resulted in a dose of 0.52 SEDs required to increase 25(OH)D significantly by 1 nmol l^−1. Artificial UVB was thus at least 8 times more efficient in increasing 25(OH)D than solar UVR at a UV-exposed area consisting of approximately hands and face. Solar UVR exposure of larger areas may lead to enhanced efficacy but was not relevant for this comparison. Significant solar-induced Δ25(OH)D was present earliest at April 8, maximal by early August and decreased by late August.

[1]  P. Philipsen,et al.  A small suberythemal ultraviolet B dose every second week is sufficient to maintain summer vitamin D levels: a randomized controlled trial , 2012, The British journal of dermatology.

[2]  H. Wulf,et al.  Vitamin D production depends on ultraviolet‐B dose but not on dose rate: A randomized controlled trial , 2011, Experimental dermatology.

[3]  H. Wulf,et al.  Interdependence between body surface area and ultraviolet B dose in vitamin D production: a randomized controlled trial , 2011, The British journal of dermatology.

[4]  H. Wulf,et al.  Variables in full‐body ultraviolet B treatment of skin diseases , 2010, Photodermatology, photoimmunology & photomedicine.

[5]  H. Wulf,et al.  Vitamin D production after UVB exposure depends on baseline vitamin D and total cholesterol but not on skin pigmentation. , 2010, The Journal of investigative dermatology.

[6]  H. Wulf,et al.  Vitamin D Level in Summer and Winter Related to Measured UVR Exposure and Behavior , 2009, Photochemistry and photobiology.

[7]  Patrick Taffé,et al.  Rate of undesirable events at beginning of academic year: retrospective cohort study , 2009, BMJ : British Medical Journal.

[8]  J B Wong,et al.  Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials , 2009, BMJ : British Medical Journal.

[9]  D. Kiel,et al.  Dietary Calcium and Serum 25‐Hydroxyvitamin D Status in Relation to BMD Among U.S. Adults , 2009, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[10]  E John Orav,et al.  Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials. , 2009, Archives of internal medicine.

[11]  C. Wagner,et al.  Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents , 2008, Pediatrics.

[12]  B. Hollis,et al.  Ultraviolet-B radiation increases serum 25-hydroxyvitamin D levels: the effect of UVB dose and skin color. , 2007, Journal of the American Academy of Dermatology.

[13]  David Moher,et al.  Effectiveness and safety of vitamin D in relation to bone health. , 2007, Evidence report/technology assessment.

[14]  M. Brustad,et al.  The solar UV radiation level needed for cutaneous production of vitamin D_3 in the face. A study conducted among subjects living at a high latitude (68° N) , 2007, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.

[15]  A. Webb,et al.  Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status , 2006, Photochemistry and photobiology.

[16]  Jakob Heydenreich,et al.  Miniature Personal Electronic UVR Dosimeter with Erythema Response and Time-stamped Readings in a Wristwatch , 2005, Photochemistry and photobiology.

[17]  H. Wulf,et al.  The wrist is a reliable body site for personal dosimetry of ultraviolet radiation , 2000, Photodermatology, photoimmunology & photomedicine.

[18]  A. Prentice,et al.  Vitamin D: seasonal and regional differences in preschool children in Great Britain , 1999, European Journal of Clinical Nutrition.

[19]  S. Seidenari,et al.  In vivo assessment of n‐alkyl‐sulfate‐induced skin irritation by means of non‐invasive methods , 1998, Skin research and technology : official journal of International Society for Bioengineering and the Skin (ISBS) [and] International Society for Digital Imaging of Skin (ISDIS) [and] International Society for Skin Imaging.

[20]  B. Dawson-Hughes,et al.  Seasonal changes in plasma 25-hydroxyvitamin D concentrations of young American black and white women. , 1998, The American journal of clinical nutrition.

[21]  B L Diffey,et al.  The standard erythema dose: a new photobiological concept , 1997, Photodermatology, photoimmunology & photomedicine.

[22]  H. Wulf,et al.  Threshold level for measurement of UV sensitivity: reproducibility of phototest , 1996, Photodermatology, photoimmunology & photomedicine.

[23]  M. Holick,et al.  McCollum Award Lecture, 1994: vitamin D--new horizons for the 21st century. , 1994, The American journal of clinical nutrition.

[24]  M. Holick,et al.  Sunlight regulates the cutaneous production of vitamin D3 by causing its photodegradation. , 1989, The Journal of clinical endocrinology and metabolism.

[25]  T. Fitzpatrick.  The validity and practicality of sun-reactive skin types I through VI. , 1988, Archives of dermatology.

[26]  R. Anderson,et al.  Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. , 1982, Science.

[27]  R. Chesney,et al.  Seasonal fluctuations in serum concentrations of vitamin D metabolites in normal subjects. , 1981, British medical journal.