Rachel's post was:
><<  According to Reinhold Vieth, a researcher, Univ. of
> Toronto, adults may need at minimum five times the RDA or 1,000 I.U. of
> vitamin D per day to protect against cancers, bone fractures, and to derive
> other broad range health benefits. ( May 1999, Am  J Clin Nutr) >>

>S.B. Feldman" responded:
>And what about sunshine: Is there enough for the chemical transformations to
>proceed with these raw materials?

Most people don't get enough daily sun exposure to stimulate sufficient
bodily production of vitamin D for optimal health.  On the other hand, as
jeanclaude pointed, out dietary sources are not sufficient to provide the
amount of vitamin D we need for optimal health, espcially if you go out with
suncreen on, or you sit in the shade, or you don't expose much skin, or
don't go out in the sun often (or daily).  We need both dietary and sunlight
sources.  Unfortunately, modern people are usually deficient in both
sources.

*On a sunny summer day, total body sun exposure produces approximately
10,000 IU of vitamin D per day.  As a result, concersn about toxic overdose
with dietary supplements that exceed 800 IU are porly founded,* says Dr.
Reinhold Vieth. (Nutrition Science News, March 2000, vol. 5, no. 3.  This is
a great article and I cannot quote the entire thing here.  But there's a lot
of meat to it!!)

Veith adds:  *Few vitamins can provide an array of health benefets as
vitamin D....lack of sunlight exposure could lead to more than thinning
bones and an increased risk for cancer--and the added benefit of controlling
cholesterol. (see below for more on this)  Vitamin D-3 is believed to
exhibit the most potent cancer-inhibiting properties and is the preferred
form of the vitamin.*

jean-claude asked:
if somebody could explain the physiology of vit D in relation with
>cholesterol intake and light exposure or could direct toward a clear
>explanation of it, it would be great.

*Vitamin D precursors require cholesterol for conversion into the
hormone-vitmamin. [vitamin D is technically a hormone]. Without adequate sun
exposure, vitamin D precursors turn to cholesterol instead of the vitamin.
The increased concentration of blood cholesterol during winter months and
the fact that outdoor activity (gardening) is associated with lower
circulating cholesterol levels in the summer, but not in winter, may explain
geographical differences in coronary heart disease incidence. (Grimes DS< et
al. Sunlight, cholesterol and coronary heart disease.  QJ Med 1996;89:
579-89)

There's more I'd love to post, but I'm not into typing the entire
article........ :-o

>I have questions is sunshine exposure thru glass windows an effective vit D
production
>enhancer, ?

No.

>is the light coming thru an igloo is able to help a naked innuit.?
NO.

>is a fire light able to emit UV or the other vibrations responsible for vit
>D metabolism.?
NO.

>what about artificilial lights?
NO.
>
Don & Rachel