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Niacin, also known as nicotinic acid or vitamin B3, is a water-soluble vitamin whose derivatives such as NADH play essential roles in energy metabolism in the living cell. The designation vitamin B3 also includes the amide form, nicotinamide or niacinamide. Severe lack of niacin causes the deficiency disease pellagra, whereas a mild deficiency slows down the metabolism, which in turn decreases cold tolerance and is a potential contributing factor towards obesity. Nicotinic acid was first discovered from the oxidation of nicotine. When the properties of nicotinic acid were discovered, it was thought prudent to choose a name to dissociate it from nicotine and to avoid the idea that either smoking provided vitamins or that wholesome food contained a poison. The resulting name 'niacin' was derived from nicotinic acid + in. Nicotinic acid reacts with hemoglobin and myoglobin in meat to form a brightly coloured complex, and thus has been used as a food additive, typically to improve the colour of minced (ground) meat. However, sometimes excess niacin is added to the meat during processing. Though still licensed as a food colouring agent in some countries, it is not licensed as such in Europe. The liver can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely slow and requires vitamin B6; 60 mg of tryptophan are required to make one milligram of niacin. Bacteria in the gut may also perform the conversion but are inefficient. For this reason, eating lots of tryptophan is not an adequate substitute for consuming niacin. Because niacin in large quantities is a vasodilator, large doses of niacin (either from vitamin B3 tablets or from treated meats) may cause harmless and short-lived but unpleasant symptoms such as extreme skin flushing resembling a sunburn, itching, gastric disturbances, and lowering of blood pressure. The amide form (strictly speaking a provitamin) does not cause these side effects, but is also not as easily assimilated by the body. Large doses of niacin are sometimes prescribed to combat high blood pressure, and also to lower blood cholesterol levels. Pharmacologic doses of niacin (1.5 to 6 grams/day) reduce LDL cholesterol levels by 10 to 25 percent and triglyceride levels by 20 to 50 percent. HDL cholesterol levels are also increased by 15 to 35 percent.1 Brand-name medications include Niaspan®, Niacor® and Nicolor®. Treatment doses cause flushing in individuals not previously exposed to large doses of niacin, so titration to increasing doses is necessary upon starting the medication. Vitamin B3 has also been used to treat schizophrenia and other mental illnesses by orthomolecular practitioners. Usually the nicotinamide form is used, as it is considered to be more effective. Unfortunately there is little scientific evidence that this treatment is effective. Because niacin promotes metabolism, some believe that taking large doses will speed up the elimination of THC from the body and produce a negative result for marijuana on a drug test. There is no evidence that this is effective, and niacin is toxic to the skin and liver in overdose. There is also anecdotal evidence that doses of 500-1000mg can terminate a bad trip on LSD or enhance the MDMA experience. BiosynthesisThe 5-membered aromatic heterocycle of the essential amino acid, tryptophan, is cleaved and rearranged with the alpha amino group of tryptophan into the 6-membered aromatic heterocycle of niacin. Food SourcesAnimal products: Plant Products:
References
Data originally published on Wikipedia |