On Wed, 28 Oct 2009 17:11:34 +0100, "Tim C." 
wrote:

>On Wed, 28 Oct 2009 16:01:21 +0000, Stephen Wolstenholme wrote in post :
><news:ceoge59nj6hr6kfcherl90n2maki0oplj2@4ax.com> :
>
>>>>>If you eat oily fish regularly you get enough vitamin D.
>>>>
>>>>There are, at least, five different forms of vitamin D. D3 is only
>>>>made in the skin and you can't get it from natural foods. Ideally we
>>>>should get vitamin D from both food and from sunlight. D3 is added to
>>>>some foods but not, so far as I know, to oily fish.
>>>
>>>Tell me how the Inuits survive?
>> 
>> The amount of sunlight required on the hands and/or face to get a
>> survival level of D3 is quite low.
>
>I don't know much about this. So we don't need very much sunlight to
>produce sufficient D3 in the skin?  Is it visible sunlight or UV that makes
>it? And is diffused light enough or do I really need direct sunlight? 
>(I get out enough anyway so I'm just asking out of curiosity.)

Ideally you need 15 minutes of direct sunlight on your face or hands.
If it's diffused sunlight you will need a lot more. It is the UVB part
of the light that does the work and that gets filtered out by glass. 

Steve

-- 
Neural Planner Software Ltd                  www.NPSL1.com

On Wed, 28 Oct 2009 16:48:42 +0000, Stephen Wolstenholme wrote in post :
<news:3msge5ho77a9j93hqjsqt6eljsmtd8etq9@4ax.com> :

> On Wed, 28 Oct 2009 17:11:34 +0100, "Tim C." 
> wrote:
> 
>>On Wed, 28 Oct 2009 16:01:21 +0000, Stephen Wolstenholme wrote in post :
>><news:ceoge59nj6hr6kfcherl90n2maki0oplj2@4ax.com> :
>>
>>>>>>If you eat oily fish regularly you get enough vitamin D.
>>>>>
>>>>>There are, at least, five different forms of vitamin D. D3 is only
>>>>>made in the skin and you can't get it from natural foods. Ideally we
>>>>>should get vitamin D from both food and from sunlight. D3 is added to
>>>>>some foods but not, so far as I know, to oily fish.
>>>>
>>>>Tell me how the Inuits survive?
>>> 
>>> The amount of sunlight required on the hands and/or face to get a
>>> survival level of D3 is quite low.
>>
>>I don't know much about this. So we don't need very much sunlight to
>>produce sufficient D3 in the skin?  Is it visible sunlight or UV that makes
>>it? And is diffused light enough or do I really need direct sunlight? 
>>(I get out enough anyway so I'm just asking out of curiosity.)
> 
> Ideally you need 15 minutes of direct sunlight on your face or hands.
> If it's diffused sunlight you will need a lot more. It is the UVB part
> of the light that does the work and that gets filtered out by glass. 
> 
> Steve

Right, thanks. 
-- 
Tim C.