![]() ![]() Inuit have adapted to this insufficiency through physiological changes: receptors that bind more tightly to the vitamin D molecule a lower set-point for calcium-regulated release of parathyroid hormone and conversion of vitamin D at a higher rate from its common form to its most active form. According to a study from Nunavut and the Northwest Territories, even Inuit on a traditional diet get less than the recommended minimum of 10 µg/day ( Kolahdooz et al. ![]() Some vitamin D is obtained from the diet, i.e., fatty fish and certain marine mammals, but such sources are insufficient. Above the Arctic Circle, solar UV is usually too weak to permit vitamin D synthesis in the skin. There has apparently been selection to reduce vitamin D requirements among the Inuit people of Alaska, northern Canada and Greenland ( Frost 2012 Frost 2018). Consequently, natural selection will favor those individuals who use this vitamin more efficiently or have alternate metabolic pathways. ![]() If solar UV is too weak or the skin too dark, there will be insufficient synthesis of vitamin D in the skin. Vitamin D requirements vary from one human population to another.
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