Impact of Orientation on the Vitamin D Weighted Exposure of a Human in an Urban Environment.
Int J Environ Res Public Health. 2017 Aug 16;14(8). pii: E920. doi: 10.3390/ijerph14080920.
10 minute walk at noon on a clear day in Germany (no clouds, haze, smog)
| Spring | head + hands | 7% of skin | 1400 IU |
| Summer | head + hands + arms | 20% of skin | 250 IU |
Note:
- Assumes White skin
Dark skin can be 2X to 5X less responsive - Assumes not obese
more than half of Vitamin D goes to fat cells, not to the body - Assumes young
only about 1/3 as much vitamin D is generated by elderly skin - Assumes same amount generated by each skin area
see Little Vitamin D generated by face and hands - June 2015 - Assumes an unspecified amount of head hair
- Assumes same skin response regardless of the time of year
seems unlikely - Vitamin D winter does not appear to exist
See also Vitamin D Life
- Time in sun (in Spain) to get 4,000 IU of vitamin D: half hour in July , 2 hours in October – Sept 2016 A small amount more skin area 25% summer, 10% Oct
- Optimize vitamin D from the sun - 14 ways
- Increase your vitamin D from the sun by wearing a tan-through instead of standard shirt
About 2,100 IU in summer with tan-thru shirt (1.5 X 1400 IU) - Vitamin D from phototherapy lamps, tanning beds, and the sun – Jan 2012
- Getting Vitamin D into your body the sun is just one of many ways
- Founder of Vitamin D Life uses a UVB bulb in the winter - next to exercycle
No – 10 minutes per day of sun-UVB is NOT enough contains the following summary
- 5-10 minutes provides only 1,000 IU ONLY IF you are near the equator
- AND young
- AND not obese
- AND have light skin
- AND it is summer
- AND it is the middle of the day
- AND you have lots of skin exposed to the sun
- AND you are lying down
- AND you are not wearing sunscreen
- AND you have a healthy Liver
- AND no clouds and nor air pollution
- AND you have good response to sunshine (4X variation between individuals)
Download the PDF from Vitamin D Life
Schrempf M1, Thuns N2, Lange K3, Seckmeyer G4.
1 Institute of Meteorology and Climatology, Leibniz Universität Hannover, 30419 Hannover, Germany. schrempf at muk.uni-hannover.de.
2 Institute of Meteorology and Climatology, Leibniz Universität Hannover, 30419 Hannover, Germany. thuns at muk.uni-hannover.de.
3 Institute of Meteorology and Climatology, Leibniz Universität Hannover, 30419 Hannover, Germany. lange at muk.uni-hannover.de.
4 Institute of Meteorology and Climatology, Leibniz Universität Hannover, 30419 Hannover, Germany. seckmeyer at muk.uni-hannover.de.
The vitamin D₃-weighted UV exposure of a human with vertical posture was calculated for urban locations to investigate the impact of orientation and obstructions on the exposure. Human exposure was calculated by using the 3D geometry of a human and integrating the radiance, i.e., the radiant energy from the direct solar beam and the diffuse sky radiation from different incident and azimuth angles. Obstructions of the sky are derived from hemispherical images, which are recorded by a digital camera with a fisheye lens. Due to the low reflectivity of most surfaces in the UV range, the radiance from obstructed sky regions was neglected. For spring equinox (21 March), the exposure of a human model with winter clothing in an environment where obstructions cover 40% of the sky varies by up to 25%, depending on the orientation of the human model to the sun. The calculation of the accumulated vitamin D₃-weighted exposure of a human with winter clothing walking during lunch break shows that human exposure is reduced by the obstruction of buildings and vegetation by 40%.
PMID: 28813022 PMCID: PMC5577621 DOI: 10.3390/ijerph14080920