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At the start of this century Inuits were largely carnivorous eating mainly seal meat. They showed no tendency to increased vascular or renal disease, and thus became a continuing source of interest to dieticians. In 1921 Stefanssen wrote The Friendly Arctic describing his 11-1/2 years in the Arctic circle, for 9 of which he subsisted on the Eskimo diet. During this time he was in splendid physical condition. Stefanssen says in his book. ) One of the puzzles about Stefanssen's experiences is how he avoided getting scurvy.

Vitamin C The discovery of plant and citrus extracts which cured scurvy has already been described. An inability to synthesize ascorbic acid is found only in primates and guinea pigs. That guinea pigs required an anti-scorbutic factor in their diet was shown by Hoist and Frolich (1907). By 1924 a highly purified anti-scorbutic factor had been obtained from lemons. In unrelated studies not concerned with nutrition but with oxido-reducing systems a strongly reducing "hexuronic acid" was isolated by Albert Szent-Gyorgi, then in Gowland Hopkins' laboratory, from adrenal glands and citrus fruits.

The disorders, which have not been identified in man, were corrected by wheat-germ oil, from which tocopherol, the active ingredient, was isolated in 1936. In spite of intensive investigations and a recognition that the vitamin is an antioxidant and destroyer of free radicals, the function of vitamin E remains obscure. The last of the fat-soluble vitamins to be identified was vitamin K, found by Dam to be an anti-hemorrhagic factor for young chicks, distinct from vitamin C. Its structure was determined by Dam in collaboration with Karrer.