Answer here:
http://www.vitamindcouncil.org/
Quote:
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Caucasian skin produces approximately 10,000 IU vitamin D in response to 20–30 minutes summer sun exposure—50 times more than the US government's recommendation of 200 IU per day!
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This is a generalization, and dependent on skin pigmentation.
The darker the skin, the longer required.
It is also thought that older people are less efficient in this than younger.
Also cofactors are needed:
Quote:
Vitamin D's Co-factors
Vitamin D has co-factors that the body needs in order to utilize vitamin D properly. They are:
* magnesium
* zinc
* vitamin K2
* boron
* a tiny amount of vitamin A
Magnesium is the most important of these co-factors. In fact, it is common for rising vitamin D levels to exacerbate an underlying magnesium deficiency. If one is having problems supplementing with vitamin D, a magnesium deficiency could be the reason why.
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All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
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Weezie looking at petunias 8.25.2017
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