Chalcraft, Jenna R.Cardinal, Linda M.Wechsler, Perry J.Hollis, Bruce W.Gerow, Kenneth G.Alexander, Brenda M.Keith, Jill F.Larson-Meyer, D. Enette2020-08-212020-08-212020-07-27Chalcraft, J.R.; Cardinal, L.M.; Wechsler, P.J.; Hollis, B.W.; Gerow, K.G.; Alexander, B.M.; Keith, J.F.; Larson-Meyer, D.E. Vitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and Women. Nutrients 2020, 12, 2237.http://hdl.handle.net/10919/99816Older adults are frequently cited as an at-risk population for vitamin D deficiency that may in part be due to decreased cutaneous synthesis, a potentially important source of cholecalciferol (vitamin D₃). Previous studies found that cutaneous D₃ production declines with age; however, most studies have been conducted ex vivo or in the photobiology lab. The purpose of this study was to characterize the response of vitamin D metabolites following a 30-min bout of sun exposure (15-min each to the dorsal and ventral sides) at close to solar noon in younger and older adults. Methods: 30 healthy individuals with skin type II/III were recruited; a younger cohort, aged 20&ndash;37 (<i>n</i> = 18) and an older cohort (<i>n</i> = 12), age 51&ndash;69 years. Exposure was at outer limits of sensible sun exposure designed to enhance vitamin D synthesis without increasing risk of photo ageing and non-melanoma skin cancer. Serum D₃ concentration was measured at baseline, 24, 48 and 72 h post-exposure. Serum 25(OH)D was measured at baseline and 72 h post-exposure plus 168 h post-exposure in the older cohort. Results: D₃ increased in response to sun exposure (time effect; <i>p</i> = 0.002) with a trend for a difference in D₃ between cohorts (time*group; <i>p</i> = 0.09). By regression modeling of continuous data, age accounted for 20% of the variation in D₃ production. D₃ production decreased by 13% per decade. Despite changes in D₃, however, serum 25(OH)D did not change from baseline to 72 or 168 h post exposure (<i>p</i> &gt; 0.10). Conclusions: Serum D₃ concentration increased significantly in response to outdoor sun exposure in younger and older adults. While ageing may dampen cutaneous synthesis, sunlight exposure is still a significant source of vitamin D₃.application/pdfenCreative Commons Attribution 4.0 Internationalageingolder personssensible sun exposurecutaneous synthesisvitamin D3natural sunlightserum 25(OH)DArticle - Refereed2020-08-21https://doi.org/10.3390/nu12082237