Background: Advice about how to balance the risks and benefits of sun exposure, and the time needed to avoid vitamin D deficiency, varies between organisations. In light of this, the purpose of this study was to calculate the time in the sun necessary to maintain existing 25(OH)D concentration throughout the year, at various locations across Australia and New Zealand, with different clothing coverage1. This information is critical to informing public health policy when considering the risks and benefits of sun exposure.
Methods: We used a microsimulation model2 to estimate changes in monthly 25(OH)D concentration using data on standard erythemal dose, solar zenith angle and climatological ozone. We estimated the number of standard vitamin D doses per 10 minute interval, and used a dose-response equation to determine the minimum time in the sun to maintain existing 25(OH)D concentration according to month and time of day
Results: Across all locations in summer, 5-10 minutes outdoors between 8am and 4pm on most days of the week, with 35% of the body surface area exposed, is sufficient to maintain existing 25(OH)D concentration. In winter, at mid-to-high latitudes, time outdoors during the middle of the day is required.
Conclusion: Provided sufficient skin is exposed, a small amount of time outdoors will maintain existing 25(OH)D concentration across most of Australia and New Zealand, with the exception of higher latitude locations in winter. These data can be used to inform guidelines regarding maintaining vitamin D via sun exposure, and may help health practitioners identify patients who may be vitamin D deficient. This presentation will also present the findings on the expected health and healthcare costs if sub-populations amended their sun exposure to optimise health outcomes for five sun-related conditions; melanoma, keratinocyte skin cancer, cataract, multiple sclerosis and fragility fractures.