"people of the north have a highly evolved physiology that makes them well suited to life in the arctic: a compact build that conserves warmth, a faster metabolism, optimally distributed body fat, and special modifications to the circulatory system." -- internet :) also, they eat mostly raw or kind of raw forms of meat, cooking meat destroys many of the vitamins that are in it. and as Thomas mentions above, organs of caribou and skin of beluga has Vitamin C in it too.
Although the Inuit diet is very high in protean and fat from the animals that they eat, they do also eat plants. The Inuit do not traditionaly cultivate plants but they do collect and eat a variety of grasses, roots, tubers, berries and seaweed when these are available. Red and brown seaweeds are a good source of vitamin C.
This was solved by Amundsen's crew eating fresh seal meat, rather than the scurvy ridden Scott's party who relied on tinned supplies and pemmican.See Roland Huntford's book.
When I first started working with birds of prey, a hawk was brought to me in very bad shape. Part of the problem was the diet the person who found her had been trying to keep her on. It was muscule meat, mainly beef. To correct the problem I started feeding her whole animals. At first she ate mainly the heads and entrails. Her diet problems were corrected in days. I believe the Inuit eat almost the entire animal as well.