Original articleEstimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes
Section snippets
Methods
For this study, we used the previously validated FastRT simulation tool and associated vitamin D calculations.8, 10, 11 FastRT is based on look-up tables of simulated atmospheric transmittances for selected scenarios. This simulation tool8 was used along with a recently published Commission Internationale de L'Eclairage vitamin D–effective action spectrum12 (Fig 1) to determine both ultraviolet (UV) B (UVB) irradiances (http://nadir.nilu.no/∼olaeng/fastrt/fastrt.html) and exposure times (//zardoz.nilu.no/~olaeng/fastrt/VitD_quartMEDandMED.html
UVB radiation
Fig 2 demonstrates changes in UVB irradiance in Boston, MA, and Miami, FL, during the months of January, April, July, and October, between the hours of 9 am and 5 pm EST. The UVB irradiance is highest around 12 to 1 pm EST compared with other times of day, in the summer months compared with winter months, and in Miami, FL, compared with Boston, MA.
Vitamin D equivalencies
Table I, Table II (available at www.eblue.org) show the estimated amount of time required to synthesize the oral equivalent of 400 and 1000 IU
Discussion
Sources of vitamin D include foods, supplements, and UVB-mediated cutaneous synthesis. Endogenous vitamin D production requires UV exposure from the sun, a well-known environmental cause of skin cancer.20 Current guidelines by the American Academy of Dermatology and the International Agency for Research on Cancer (IARC), a branch of the World Health Organization, do not recommend intentional unprotected sun exposure as a vitamin D source.4, 21 However, intentional sun exposure has been
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2021, Clinical NutritionCitation Excerpt :As there are very few natural sources of vitamin D in food, diet does not provide adequate amounts of vitamin D for most people [4,5]. Hence, in many situations in which sunlight exposure is inadequate, supplementation with vitamin D may be necessary [3,4,6,7]. An example of this situation is the confinement of people during the current coronavirus disease 2019 (COVID-19) pandemic.
Funding sources: None.
Conflicts of interest: None declared.
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These two authors have equal responsibility for the work described herein.