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| Birth Name(s) : Vitamin C |
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Full Vitamin C Biography
Vitamin C or L-ascorbate is an essential nutrient for higher primates, and a small number of other species. The presence of ascorbate is required for a range of essential metabolic reactions in all animals and in plants and is made internally by almost all organisms, humans being one notable exception. It is widely known as the vitamin whose deficiency causes scurvy in humans. It is also widely used as a food additive.
The pharmacophore of vitamin C is the ascorbate ion. In living organisms, ascorbate is an antioxidant, as it protects the body against oxidative stress, and is a cofactor in several vital enzymatic reactions.
Most simians consume the vitamin in amounts 10 to 20 times higher than that recommended by governments for humans. This discrepancy constitutes the basis of the controversy on current recommended dietary allowances (see Vitamin C as a macronutrient - Evolutionary rationales).
An adult goat, a typical example of a vitamin C-producing animal, will manufacture more than 13,000 mg of vitamin C per day in normal health and the biosynthesis will increase "many fold under stress". Trauma or injury has also been demonstrated to also use up large quantities of vitamin C in humans. Some microorganisms such as the yeast Saccharomyces cerevisiae have been shown to be able to synthesize vitamin C from simple sugars.
Scurvy is an avitaminosis resulting from lack of vitamin C, as without this vitamin, the synthesised collagen is too unstable to meet its function. Scurvy leads to the formation of liver spots on the skin, spongy gums, and bleeding from all mucous membranes. The spots are most abundant on the thighs and legs, and a person with the ailment looks pale, feels depressed, and is partially immobilized. In advanced scurvy there are open, suppurating wounds and loss of teeth and, eventually, death. The human body can store only a certain amount of vitamin C., and so the body soon depletes itself if fresh supplies are not consumed through the digestive system.
In 1957 the American J.J. Burns showed that the reason some mammals were susceptible to scurvy was the inability of their liver to produce the active enzyme L-gulonolactone oxidase, which is the last of the chain of four enzymes which 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.
High doses (thousands of milligrams) may result in diarrhea. Proponents of alternative medicine (specifically orthomolecular medicine) claim the onset of diarrhea to be an indication of where the body’s true vitamin C requirement lies. Both Cathcart and Cameron have hypothesized that very sick patients with cancer or influenza do not display any evidence of diarrhea at all until ascorbate intake reaches levels as high as 200 grams (nearly half a pound).United States vitamin C recommendations
Humans carry a mutated and ineffective form of the gene required by all mammals for manufacturing the fourth of the four enzymes that manufacture vitamin C. The inability to produce vitamin C, hypoascorbemia, is, according to the Online Mendeleian Inheritance in Man database, a "public" inborn error of metabolism.
Simple tests use DCPIP to measure the levels of vitamin C in the urine and in serum or blood plasma. However these reflect recent dietary intake rather than the level of vitamin C in body stores. Reverse phase high performance liquid chromatography is used for determining the storage levels of vitamin C within lymphocytes and tissue.
While being harmless in most typical quantities, as with all substances to which the human body is exposed, vitamin C can still cause harm under certain conditions.
The overwhelming majority of species of animals and plants synthesise their own vitamin C, making some, but not all, animal products, sources of dietary vitamin C.
"Serum and plasma vitamin C measurements do not correlate well with tissue levels while lymphocyte vitamin C levels provide the most accurate assessment of the true status of vitamin C stores and are not affected acutely by circadian rhythm or dietary changes."^ Yamada H, Yamada K, Waki M, Umegaki K. (2004). "Lymphocyte and Plasma Vitamin C Levels in Type 2 Diabetic Patients With and Without Diabetes Complications" (PDF). Diabetes Care 27: 2491–2. |
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