Background
The World Health Organization recommends a daily intake of 45 mg/day of vitamin C for healthy adults. Vitamin C is necessary for production of collagen and other biomolecules, and for the prevention of scurvy. Vitamin C is an antioxidant, which has led to its endorsement by some researchers as a complementary therapy for improving quality of life. Since the 1930s, when it first became available in pure form, some physicians have experimented with higher than recommended vitamin C consumption or injection.
Primates, including humans, and guinea pigs do not synthesize vitamin C internally. Nearly all other animals synthesize vitamin C internally, maintaining cellular vitamin C concentrations that are considerably higher than those achieved with the Recommended Daily Intake set for humans. Irwin Stone coined the term hypoascorbia to describe the low level of vitamin C maintained in humans through their diet compared to the level other animals maintain through their internal production. He proposed that hypoascorbia is caused by a genetic defect in humans and most primates. Animals that produce ascorbate internally produce considerably higher amounts when they are stressed.
Vitamin C has been promoted in alternative medicine as a treatment for the common cold, cancer, polio and various other illnesses. The evidence for these claims is mixed. Orthomolecular-based megadose recommendations for vitamin C are based mainly on theoretical speculation and observational studies, such as those published by Fred R. Klenner from the 1940s through the 1970s. There is a strong advocacy movement for such doses of vitamin C, and there is an absence of large scale, formal trials in the 10 to 200+ grams per day range. The single repeatable side effect of oral megadose vitamin C is a mild laxative effect if the practitioner attempts to consume too much too quickly. A tolerable upper limit (UL) of vitamin C was set at 2 grams for the first time in the year 2000, referencing this mild laxative effect as the reason for establishing the UL. This 2 g UL restricts the acceptance of formal vitamin C megadose trials by Institutional review boards.
Read more about this topic: Vitamin C Megadosage
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