><<  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) >>
>
>And what about sunshine: Is there enough for the chemical transformations
to
>proceed with these raw materials?

i suspect myself dietetary vitamin D not able to compensate for the sunchine
source ....
and that the exposure of the whole skin to sun is more impotant than the
usual recomendation of  the minimum 10 minutes of sun to to your hand and
face only.
most of the healthy hunter gatherers are often half naked even in cold
climates except the ones in extrem cold climate like the innuits and those
ones are subject to osteoporosis despite their high intake of dietetary vit
D. The lack of light is certainly a determining factor.

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.
I have questions
is sunshine exposure thru glass windows an effective vit D production
enhancer, ?
is the light coming thru an igloo is able to help a naked innuit.?
is a fire light able to emit UV or the other vibrations responsible for vit
D metabolism.?
what about artificilial lights?
jean-claude