Vitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and Women

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.

Prenatal exposure to solar radiation and hypertensive disorders of pregnancy

“…31 It is also hard to compare the efficacy of natural solar radiation and artificial UV radiation in a photobiology laboratory, where the dose of UV delivered can be controlled and directly quantified. 32 All these challenges may have deterred epidemiological research on this topic. In our analysis, the effects of solar radiation reached a plateau after the 50th percentile, and more than 45% of the daily solar radiation was observed between 10:00 and 13:00 hours from December to February.…”

“…UV exposure levels obtained in a natural environment vary in different studies due to latitude, season, personal skin pigmentation, body surface area exposed, etc 31 . It is also hard to compare the efficacy of natural solar radiation and artificial UV radiation in a photobiology laboratory, where the dose of UV delivered can be controlled and directly quantified 32 . All these challenges may have deterred epidemiological research on this topic.…”

Vitamin D, Depressive Symptoms, and Covid-19 Pandemic

“…There are several risk factors related to vitamin D deficiency such as obesity, dark skin, living in countries with low sunlight incidence, gastrointestinal malabsorption, renal insufficiency, liver disease, and the use of covered clothing and sunscreen ( Kennel et al, 2010 ; Holick et al, 2011 ). Furthermore, reduced exposure to sunlight, thereby reducing the biosynthesis of vitamin D in the skin, is a strong factor in the pathophysiology of vitamin D deficiency and studies have been demonstrated that sun exposure can enhance vitamin D synthesis ( Jorde et al, 2010 ; Chel et al, 2011 ; Macdonald et al, 2011 ; Chalcraft et al, 2020 ).…”

The challenge of achieving vitamin D adequacy for residents living in long-term care

“…Irradiation with sun or ultraviolet B radiation has been studied in LTC homes with limited success. Sun exposure can raise vitamin D levels in older adults, but it is well established that efficiency falls by 13 % per decade (13) . Residents with dark skin pigmentation would require impractical longer exposure times for meaningful vitamin D synthesis (12) .…”