>It doesn't replace getting real sunlight though. Or if you're an Inuit, eating polar bear livers.
Not that I expect HN readers to likely end up in a situation where they have to decide whether to eat a polar bear liver, but that is definitely a part of the polar bear that no one should eat:
>...A polar bear’s liver contains an extremely high concentration of vitamin A. This is due to their vitamin A rich diet of fish and seals. The Eskimos have long been wary of eating the polar bear for this reason, but it’s something the early Artic explorers found out the hard way.
Ingesting the liver can cause vitamin A poisoning known as acute hypervitaminosis A. This results in vomiting, hair loss, bone damage and even death. So although actually capturing a polar bear may seem life threatening, it turns out that eating its liver is just as deadly.
Oh, I was thinking of animal fat in general. They have some minor genetic adaptations to get more vitamin D from it (since there's not much sunlight) and after moving away from the traditional high-fat diets now lack it as much as anyone else.