Huh, weird. I would have assumed deficiency would be inversely proportional to amount of sunshine. Do people in northern europe really experience so much more “sun on skin” time or is it wholly diet driven?

Melanin reduces the amount of vitamin D synthesized in the skin for the same reason it has protective effects against sunburns.

Historically this wasn't a problem since people with more melanin live in sunnier, more UV intense regions. In fact, pale skin may have been an adaptation as people moved north from the equator to combat the decrease in sun exposure/intensity. But people spend much less time outdoors today with AC and the internet, so vitamin D deficiency is especially prominent in dark skinned populations.

From that link:

> The generally adequate vitamin D status in the Nordic countries is due to the use of cod liver oil and supplements (46) and vitamin D fortification, leading to a great improvement in Finland during the last decade (47).

Doesn't surprise me; here in the South we don't get deficient enough to cause obvious issues, so we don't pay attention to it.

Are you African-American? (Assuming you mean Southern US)

Southern Europe :)

At least in Sweden all children are given supplements, up to at least the age of 5, and just anecdotal, many of friends and grownups in my extended family do so too.