Abstract
Older 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 20–37 (n = 18) and an older cohort (n = 12), age 51–69 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; p = 0.002) with a trend for a difference in D3 between cohorts (time*group; p = 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 (p > 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.
Highlights
Accumulating evidence has documented that vitamin D deficiency is associated with the onset and progression of a variety of chronic diseases including cardiovascular disease, type 2 diabetes, immune system diseases, neuropsychiatric disorders and certain cancers [1]
The present study suggests that a single session of solar exposure to both the front and back-sides of the body at the outer limits of the “sensible sun exposure” guidelines was sufficient to promote D3 synthesis in most individuals aged 20 to 69 years who self-identified with skin types II and III, and that some individuals may be non-responsive to a single exposure
A single 30-min bout of sun exposure during late spring at close to solar noon was sufficient to observe an increase in vitamin D3 concentration within 24 to 48 h in a cohort of younger and older adults as has been previously observed in the photobiology laboratory with a measured dose of UVB
Summary
Accumulating evidence has documented that vitamin D deficiency is associated with the onset and progression of a variety of chronic diseases including cardiovascular disease, type 2 diabetes, immune system diseases, neuropsychiatric disorders and certain cancers [1]. Older adults are frequently cited as an at-risk population for vitamin D deficiency [2,3,4]. Nutrients 2020, 12, 2237 of vitamin D deficiency (serum 25(OH)D 60 to 65 years) that varies by location and ethnicity, and ranges from 12.1% of individuals with mixed ancestry in Greater Toronto (43◦ N) [5] to 37.3% in Mexico (
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