Comment by shagie

> (how do the inuit do it? perhaps their diet has enough vitamin d even without sun?)

Two parts:

First, they're not exposing their skin to the sun. There's no reason to have paler skin to get more UV if it's covered up most of the year.

Secondly, for the Inuit diet there are parts that are very Vitamin D rich... and there are still problems.

Vitamin D-rich marine Inuit diet and markers of inflammation – a population-based survey in Greenland https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709837/

> The traditional Inuit diet in Greenland consists mainly of fish and marine mammals, rich in vitamin D. Vitamin D has anti-inflammatory capacity but markers of inflammation have been found to be high in Inuit living on a marine diet

Vitamin D deficiency among northern Native Peoples: a real or apparent problem? - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3417586/

> Vitamin D deficiency seems to be common among northern Native peoples, notably Inuit and Amerindians. It has usually been attributed to: (1) higher latitudes that prevent vitamin D synthesis most of the year; (2) darker skin that blocks solar UVB; and (3) fewer dietary sources of vitamin D. Although vitamin D levels are clearly lower among northern Natives, it is less clear that these lower levels indicate a deficiency. The above factors predate European contact, yet pre-Columbian skeletons show few signs of rickets—the most visible sign of vitamin D deficiency. Furthermore, because northern Natives have long inhabited high latitudes, natural selection should have progressively reduced their vitamin D requirements. There is in fact evidence that the Inuit have compensated for decreased production of vitamin D through increased conversion to its most active form and through receptors that bind more effectively. Thus, when diagnosing vitamin D deficiency in these populations, we should not use norms that were originally developed for European-descended populations who produce this vitamin more easily and have adapted accordingly.

Vitamin D intake by Indigenous Peoples in the Canadian Arctic - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10260879/

> Vitamin D is an especially fascinating nutrient to study in people living in northern latitudes, where sun exposure is limited from nearly all day in summer to virtually no direct sun exposure in winter. This essential nutrient is naturally available from synthesis in the skin through the action of UVB solar rays or from a few natural sources such as fish fats. Vitamin D is responsible for enhancing many physiological processes related to maintaining Ca and P homeostasis, as well as for diverse hormone functions that are not completely understood.