<P> In 1957, J.J. Burns showed that some mammals are susceptible to scurvy as their liver does not produce the enzyme L - gulonolactone oxidase, the last of the chain of four enzymes that synthesize vitamin C. American biochemist Irwin Stone was the first to exploit vitamin C for its food preservative properties . He later developed the theory that humans possess a mutated form of the L - gulonolactone oxidase coding gene . </P> <P> In 2008, researchers at the University of Montpellier discovered that in humans and other primates the red blood cells have evolved a mechanism to more efficiently utilize the vitamin C present in the body by recycling oxidized L - dehydroascorbic acid (DHA) back into ascorbic acid for reuse by the body . The mechanism was not found to be present in mammals that synthesize their own vitamin C . </P> <P> Vitamin C megadosage is a term describing the consumption or injection of vitamin C in doses comparable to or higher than the amounts produced by the livers of mammals which are able to synthesize vitamin C. The theory behind this, although not the actual term, was described in 1970 in an article by Linus Pauling, a famous scientist who had been awarded the Nobel Prize in Chemistry in 1954 . Briefly, his position was that for optimal health, humans should be consuming at least 2,300 mg / day to compensate for the inability to synthesize vitamin C. The recommendation also fell into the consumption range for gorillas - a non-synthesizing near - relative to humans . A second argument for high intake is that serum ascorbic acid concentrations increase as intake increases until it plateaus at about 190 to 200 micromoles per liter (μmol / L) once consumption exceeds 1,250 milligrams . As noted, government recommendations are a range of 40 to 110 mg / day and normal plasma is approximately 50 μmol / L, so' normal' is about 25% of what can be achieved when oral consumption is in the proposed megadose range . </P> <P> Linus Pauling, famous awardee of the Nobel Prize for Chemistry, popularized the concept of high dose vitamin C as prevention and treatment of the common cold in 1970 . A few years later he proposed that vitamin C would prevent cardiovascular disease, and that 10 grams / day, initially (10 days) administered intravenously and thereafter orally, would cure late - stage cancer . Mega-dosing with ascorbic acid has other champions, among them chemist Irwin Stone and the controversial Matthias Rath and Patrick Holford, who both have been accused of making unsubstantiated treatment claims for treating cancer and HIV infection . </P>

Where is vitamin c synthesized in the body
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