Been around that block a few times. I think the bottom line is that, in the US, it is difficult-to-impossible to get enough vitamin D producing sunlight north of south Florida.
Depends on your ancestry. If a population is in a given area for more than about 500 years, the general skin tone of that population adjusts to maximize vit D production while minimizing skin damage, for the available sunlight in that area. There’s actually a mathematical formula somewhere for skin tone and average yearly sunlight. The exception is Inuit populations, who have historically gotten most of their vit D from fatty fish.
So, those of us whose ancestors came from northern latitudes are better adapted for living in the northern states. Provided we actually get out in the sun once in a while :p
This may have been a contributing factor for why black slavery wasn’t as predominant in the northernmost areas of North America or Europe. While I was doing research on this, I came across reports of African slaves imported to England, getting sick and dying rather quickly. The reports are centuries old so its hard to be sure, but I’m hypothesizing here that they suffered severe vitamin D deficiencies, which made them quite vulnerable to a number of things. Combine that with diseases they’d never encountered, they probably didn’t stand much of a chance.
All theory, of course. My time machine’s in the shop :p
“...it is difficult-to-impossible to get enough vitamin D producing sunlight north of south Florida.”
My understanding is that you don’t need the direct sunlight, just the rays from the Sun, which is abundant, even on cloudy days?