The Polar Bear, Seal etc, livers are very rich in vitaminA.That being a fat soluble vitamin, it's very difficult for our bodies to excrete.Vitamins like B and C are easily egested as they are water soluble.At high doses, the fat soluble vitamins are higly toxic and can result in death if taken in excess.But, the native people and animals have inbuilt immunities against these.Call it natural adaptation.What would kill a normal dog, the Tundra dogs happily thrive on them.Same with the Masais of Africa.Despite their high protien food, their resistance to cholestrol is high.

My ex-roomie is a PhD in Micro-Biology.

Best-

Vikram