Zuleikaa,
Sunscreen doesn't make any real difference to vitamin D levels according to the expert who cited the study.

Hutchinson,
The world authority on vitamin D is Dr. Vieth , he uses nmol/L. There are always people who get mixed up between units and you were hardly helping by using an idiosyncratic abbreviation; it was far from clear - to me at least - what was meant. Luckily the posts I linked to in my first comment have 'clickable links' in the text references which can be easily consulted. I have posted links to the text and there are links to the references in the essays, look there to find things like this -
http://www.ajcn.org/cgi/content/full/69/5/842

Is anyone seriously suggesting that if the Italian centenarians had attained and maintained 'normal' (high) serum vitamin D levels, which would require supplementing, they would not be close to death at 100 years old. I agree with that actually: I think they would be long since dead. If I am lucky enough to reach 85 I'd like to have the vitamin d level of a 50 year old; that would mean I was in excellent health. But I wouldn't force my levels up by year round ingestion of an amount of vitamin D that has no precedent in the circumstances we all evolved in.

No Inuit ever got 5000 IU a day for more than a month; it would only be possible when there was a salmon run. And you are backing this up with a sunbathing technique that may short circuit the 'D' synthesis limiting mechanism resulting in several times more 'D' than nature intended per session. Why do you think that limit hasn't been removed by natural selection? I think that it's because the people who had the vitamin D limiting trait tended to survive more than those who lacked it.

The point about African Americans is that their bone health is BETTER than other people's despite the fact their levels of the form of vitamin D that is commonly measured is lower.

There is someone on this thread talking about more than doubling their already terrifyingly high dose of vitamin D. My conscience is clear.