Journal of Exposure Science & Environmental Epidemiology (2019) https://doi.org/10.1038/s41370-019-0137-2
A. Religi, C. Backes, A. Chatelan, J.-L. Bulliard, L. Vuilleumier, L. Moccozet, M. Bochud & D. Vernez
- Get enough Vitamin D from UK winter sun (if white skin and believe that 10 ng is enough) - Aug 2018
- Vitamin D needed for 12 ng in winter in Finland – Whites 320 IU, Blacks 720 IU – July 2018
- Vitamin D needed to get children to just 20 ng in winter 800 IU white skin, 1100 IU dark (Sweden) – RCT June 2017
- 90 percent of Swiss men have less than 30 ng of vitamin D in the winter – Nov 2012
- Vitamin D from low-cost UVB lamps
- No – 10 minutes per day of sun-UVB is NOT enough
Although overexposure to solar ultraviolet radiation (UVR) is responsible for cutaneous melanoma and epithelial skin cancer and can cause negative health effects such as sunburn, a “little and often” exposure regime is often suggested to produce naturally recommended vitamin D levels, being essential for skeletal health. This study aimed to quantify solar UV doses needed to trigger 1000 International Units (IU) vitamin D doses and, at the same time, producing sunburn in Switzerland. Solar UV erythema irradiance (in mW/m2) measured at four meteorological stations in Switzerland for the period 2005–2017 were used to evaluate effective solar UV radiation producing 1000 IU vitamin D doses in skin phototype II and III individuals. Daily solar UV exposure durations (in minutes) needed to produce vitamin D with limited sunburn risk were estimated while considering mean vitamin D food intake of the Swiss population and seasonal skin coverage.
In summer and spring, with 22% of uncovered skin, 1000 IU vitamin D doses are synthesized in 10–15 min of sun exposure for adults.
Exposure durations between erythema risk and 1000 IU vitamin D production vary between 9 and 46 min.
In winter and autumn, the recommended vitamin D production without sunburn risks often unachievable, since up to 6.5 h of sun exposure might be necessary considering 8–10% of uncovered skin surface. The vitamin D food intake only represented 10% of the recommended vitamin D production and remained unchanged throughout the year. These findings might clarify why vitamin D deficiency is common in Switzerland. Moreover, exposure durations between recommended vitamin D and increased sunburn risk might only differ by few minutes. Without additional oral vitamin D supplementation, daily doses of vitamin D (1000 IU) are not reachable in autumn and winter months in Switzerland.