Morning sunshine best time for vitamin D! Myth or Fact?

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Morning sunshine best time for vitamin D! Myth or Fact?

Post by Admin on Tue 15 Apr 2014 - 14:48

Morning sunlight is very good for Vitamin D!

Is it a myth?  YES………………it is.

Sunlight does produce vitamin D but not the morning sunlight. Vitamin D3 (cholecaliciferol) is synthesized in our skin when cholesterol (7-dehydrocholesterol ) in our skin is exposed to UVB rays (ultraviolet B radiation at wavelengths of 280-315nm) present in the sunlight.
D3 is then processed in the liver to 25-hydroxy vitamin D (calcidiol), and then further processed and stored in the kidney to 1,25 dihydroxy vitamin D (calcitrol). This end substance is the one which the body uses.

To debunk this myth we need to know a bit about the ultraviolet radiation present in the sunlight. As the name suggests “ultra” it means beyond, so UV (ultra violet), beyond the color violet which our eyes cannot see. Our eyes can only see the seven colors which are in the electromagnetic wavelength of 380 -780 nanometers. Ultraviolet is further sub-divided into UVC, UVB and UVA. The electromagnetic range of UVC is 100-280nm, UVB is 280-315nm and UVA is 315-400. The UV is a very small amount of the radiation which reaches the earth’s surface, much is filtered out by the atmosphere. Only the electromagnetic wavelengths of 280-315nm which is UVB activate the production of Vitamin D in our skins.

So by now you all have guessed we need to know when does UVB rays reach the earth’s surface or fall on our skins. Yes, definitely for sure not during the morning or evening hours. When the sun’s angle is more than about 50 degrees to the earth’s horizon some UVB rays can penetrate the atmosphere/ozone layer, at angles lesser than 50 degrees it is reflected back. In other words angles higher than about 50 degrees would be 2-4 hours surrounding noon time. Of course many other factors also come into play like climate, seasons, altitude, latitude and longitude. Details for any location can be checked up at the U.S. Navy website http://aa.usno.navy.mil/data/docs/AltAz.php to determine time and angle of sun over any city.

For Bangkok on April 15th we can get UVB rays only during 09:40am to 0300pm.
For Bangkok on December 15th it would be 11:10am to 01:20pm.

10–15 minutes exposure 3–4 times a week is enough to produce the essential vitamin D. People over 50 years of age need double the time. We need not worry for excess production from sunlight as ones the reserves are met the extra is degraded as unlike from supplements which can lead to toxicity and various side effects. And 10-15 minutes are not hazardous to damage our skin. So instead of being concerned for your skin color go out for your lunch break to get some fresh air and sunshine (UVB), and get this essential vitamin for free form nature. Health outweighs beauty.

Anil Grover



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Last edited by Admin on Sun 22 Jun 2014 - 10:33; edited 5 times in total
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Re: Morning sunshine best time for vitamin D! Myth or Fact?

Post by Renu Grover on Tue 15 Apr 2014 - 16:33

Thanks for this valuable information, all this time we were really under the wrong impression that the early morning sunshine was the best...

Does this mean that we should not put on sunscreen before going out at the peak hour?

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