| 90 degrees | 60 degrees | 20 degrees |
| no shadow | shadow almost as long as person | very long shadow |
| Max vitamin D | 50% of vitamin D | zero vitamin D |
About 10X less vitamin D from the sun if stand instead of lie down in bathing suit
- Person standing has about 3X less skin exposed to the air
due to to wearing short sleeves instead of bathing suit - Person standing has about 3X less light falling on the exposed skin (for US latitudes in summer)
Based on
- person in short sleeves has 1/3 as much skin exposed as a person in a bathing suit
- No – 10 minutes per day of sun-UVB is NOT enough
Holick: difference between standing and lying down 3.5X at 30 latitude, 2X at high latitude - the following two charts from: UV creates Vitamin D
Horizontal (lie down): 80 degrees 90%, 60 degrees 50%, 40 degrees 20%, 20 degrees 0%
Vertical (standing): 80 degrees 110%, 60 degrees 75%, 40 degrees 30%, 20 degrees 0%
But, The Shadow Rule – you make more Vitamin D when you are taller than your shadow – 1992
shows lots of vitamin D can be generated in the morning at 23 degrees latitude
See also web
- Health effects of sun exposure WikiPedia
At high noon, ultraviolet radiation reaching ground level is 95% UVA and 5% UVB
. . before 10am and after 2pm this percentage changes over time to 99% UVA and 1% UVB.