Hacker News Reader

Comment by mikedilger | Hacker News Reader

I read Michael Holick's book (can't find it at the moment) he was the guy who discovered the circulating form of vitamin D.. IIRC you get vitamin D from the sun in rather large quantities. Just 15 minutes per day with only your face and hands exposed with the sun up at 45 degrees or more will be enough. I'm sure my data is not accurate, but it's in the ballpark. He has tables that depend on how dark your skin is and what latitude you live at.

View on HN

So, this is only partly true. You need direct sunlight AND the amount varies wildly depending on your skin color. If you're rather pale, it may be only 15 min. But it can go up to several hours if you're dark-skinned.

I've also read that 15 minutes is sufficient. The caveat being that it may need to be strong(ish) sunlight, otherwise you may not generate any at all.

What if it's cloudy? We are lucky to get 3 days a week where the midday sun isn't covered by cloud. Is it still sufficient filtering through the atmosphere?

UV rays penetrate clouds, but the clouds do filter some of it, so you'll likely need to increase the amount of time you spend outside depending on how cloudy it is.

Does one need exposure to direct sunlight, or sunlight coming via glass windows works?

Glass windows block the part of the UV spectrum that is needed to make Vit D.

https://www.nytimes.com/2019/02/08/well/live/does-sunlight-t...

Reply on news.ycombinator.com