Unlike most other vertebrates, humans cannot manufacture Vitamin C. So a healthy diet needs to contain sufficient Vitamin C to avoid the disorders of Vitamin C deficiency.
Linus Pauling, two time Nobel Laureate, first advocated taking large doses of vitamin C (up to 10-12 grams a day) in order to offset the deficiencies of our modern diet. He argued that the modern shift away from a diet of fruit and vegetables explained the modern epidemic of heart disease because vitamin C is required to produce the collagen necessary to inflamed and damaged arteries. A vitamin C-starved body compensates for this deficiency by increasing the production of a very small and sticky type of cholesterol known as lipoprotein A, which leads to the formation of atheromatous plaque (clogged arteries). Linus Pauling advocated taking large amounts of vitamin C in combination with the amino acid lysine to reverse the damage done to the arteries and to prevent recurrence.
James Lind (1716-1794), pioneer of naval hygiene in the British Royal Navy, conducted the first ever clinical trial proving that citrus fruits cured scurvy. Lind's discovery saved tens of thousands of seamen from the ravages of scurvy, spurring England's naval supremacy, putatively changing the course of world history.
Approximately 63 million years ago, human primate predecessors lost the gene gulnolactone oxidase pseudogene – GULOP this is responsible for the manufacture of Vitamin C from glucose. The ability to synthesize Vitamin C has been lost several times in vertebrates, e.g. in guinea pigs, some bats, some fishes, passeriform birds and in primates of the suborder Haplorrhini, which includes monkeys, apes and humans.