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Comment by sgt | Hacker News Reader

You don't need a lot of minutes outside to get a sufficient amount of sunlight to produce Vitamin D. Maybe 15-20 min a day.

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Where I live we had 14 hours of sunlight per entire January of last year. 14 hours. FOR ENTIRE MONTH. And sunrise is past 9 in the morning where entire population is already indoors working, sunset is about 3 in the afternoon.

So yeah, I maybe got 15 minutes of sun for entire January, but this is my generous guess.

Sounds like you live in Canada or Northern Norway or somewhere. I would get a UV lamp or something.

I play tennis in the Greek sun four hours a week (plus whatever other exposure) and I'm still deficient. I don't know who these levels were designed for, maybe my ancestors who were in the sun so often that they looked 50 in their thirties.

It's 0ºC here. The only exposed skin is the center of my face. I find it hard to believe 15 minutes of exposure are enough.

I regularly go outside with my shirt off at -10C, as long as there's no wind and the sun's beaming, I'm nice and warm. Got a bit of a suntan last week. Wife thinks I'm crazy :)

> The only exposed skin is the center of my face.

Me too. And I have a beard. Do I have to take that into account? Do bald men get more D-vitamin out of the sun? Studies never talk about hairiness.

Doesn't that vary with the skin color (aka melanin content in the skin)? I presume as a brown person I need more exposure for an equivalent dose compared to a Caucasian person.

It's a builtin feature of us white folks to think everyone else is also white. /s

Ha :)

Yes it does, darker skinned persons in northerly climes are at higher risk of lower vit D than we pale skins with the equal level of exposures to the sun.

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