Nutrition & Diet Vitamin D from sun exposure

Indian Summer

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A couple of years ago Stephen Walsh wrote an article in The Vegan about vitamin D and how much sun exposure was required per day for your skin to synthesize a healthy level (which in this case is said to be 25 micrograms or the equivalent of 1000 IU) of the vitamin. I was inspired by this, and especially the fact that he was using a publicly available software authored by the Norwegian Institute for Air Research.

So I decided to try it out for myself, and the result can be seen below. Some assumptions have to be made in order to calculate this. Here are mine:

Location: London
Time: Midday
Skin type: Pale caucasian
Medium ozone layer
Altitude: 50m above sea level
Surface type: Lawn
It assumes you expose your face, hands and arms. (Which is admittedly an unreasonable assumption many places in the winter.)

This is the software I used -- in fact it's a simple web application, so anyone with a browser can use it:
Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status and no sunburn - easy version

It would be interesting to generate similar plots for other times of day, other locations, other skin types, etc.

vit_D.png
 
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Indian Summer

Indian Summer

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I should add that in order to create graphs, you have to run the program many times over, collect the data for each run in files, and then use another software to do the actual graph. (I used gnuplot.) So I lied and it's a bit more work than what I said first :)
 

Pickle Juice

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It doesn't like my longitude or altitude, but it gave me a limit of eighteen minutes in the midday sun on a cloudless day.
 
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Indian Summer

Indian Summer

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It doesn't like my longitude or altitude, but it gave me a limit of eighteen minutes in the midday sun on a cloudless day.
Is that the time it takes to get sun burn? There are actually a couple of values calculated, both minimum required time to synthesise a healthy dose, and the time it takes to get sun burnt.
 

Rosie1

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This is pretty cool! I tried it but I was using Google Earth to get the long/lat but it has north and west whereas the program was asking for north and east.
So, I can't figure out how to do the long/lat.
shy.gif
 
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Indian Summer

Indian Summer

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This is pretty cool! I tried it but I was using Google Earth to get the long/lat but it has north and west whereas the program was asking for north and east.
So, I can't figure out how to do the long/lat.
shy.gif
According to Google:

To look up the geographic coordinates (latitude and longitude) of a spot on the map, follow the steps below:

Right-click on the desired spot on the map to bring up a menu with options.
In the menu, select What’s here?.
Click the green arrow to get the latitude and longitude coordinates.