The effects of a mid-winter 8-week course of sub-sunburn sunbed exposures on tanning, vitamin D status and colds

• Published in: Photochemical & photobiological sciences Vol. 11; no. 12; pp. 1848 - 1854
• Main Authors: de Gruijl, Frank R., Pavel, Stan
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2012
• Subjects: Adolescent; Adult; Biochemistry; Biomaterials; Chemistry; Cold Temperature; Dietary Supplements; Female; Humans; Male; Physical Chemistry; Plant Sciences; Seasons; Sunbathing; Tanning; Vitamin D - analogs & derivatives; Vitamin D - blood; Young Adult
• ISSN: 1474-905X; 1474-9092
• DOI: 10.1039/c2pp25179e

Like UV irradiation, which generates vitamin D 3 in the skin, the hormonally active metabolite, 1,25-dihydroxyvitamin D 3 , boosts innate immunity against viruses and bacteria. Epidemiologic studies have found high vitamin D levels to be associated with lower risk of infections of the upper respiratory tract (colds). We have therefore performed an intervention study in 105 young adults (ages 18–30 years; 91% female) over a mid-winter 8-week period (January–March 2010). The participants were randomised to 3 groups: (A) subjected to 3 times a week sub-sunburn sunbed exposure ( n = 35), (B) daily vitamin D supplementation, @ 1000 IU ( n = 37), and (C) a control group without any intervention ( n = 33). The mean serum level of 25-hydroxyvitamin D (25(OH)D) dropped from 62 to 55 nmol l −1 in group C, while these levels rose from 62 to 109 and from 58 to 93 nmol l −1 in groups A and B, respectively ( p < 0.001). The skin on the chest darkened significantly in group A (mean difference in lightness, L *, equalled −5.7, p < 0.001), correlating significantly, but weakly, with increases in 25(OH)D (3.3 nmol l −1 per unit drop in L *, R 2 = 0.17, p = 0.014). The percentage of self-reported colds with proper signs and symptoms was only slightly and not significantly reduced in groups A and B in comparison to group C: 57 and 51 versus 67%, respectively. Hence, the sub-sunburn sunbed treatment was effective in tanning and increasing the 25(OH)D serum level, more so than 1000 IU per day, but had no appreciable effect on colds.