Editing Niacin (section)

==Production==
===Biosynthesis===
[[Image:Tryptophan metabolism.svg|thumb|300px|class=skin-invert-image|Niacin, [[serotonin]] (5-hydroxytryptamine), and [[melatonin]] [[biosynthesis]] from [[tryptophan]]]]
In addition to absorbing niacin from diet, niacin can be synthesized from the [[Essential amino acid|essential]] [[amino acid]] [[tryptophan]], a five-step process with the penultimate compound being [[quinolinic acid]] (see figure). Some bacteria and plants utilize [[aspartic acid]] in a pathway that also goes to quinolinic acid.<ref>{{cite journal |vauthors=Foster JW, Moat AG |title= Nicotinamide adenine dinucleotide biosynthesis and pyridine nucleotide cycle metabolism in microbial systems |journal= Microbiol. Rev. |volume= 44 |issue= 1 |pages= 83–105 |date= 1 March 1980 |doi= 10.1128/MMBR.44.1.83-105.1980 |pmid= 6997723 |pmc= 373235}}</ref> For humans, the efficiency of conversion is estimated as requiring 60{{nbsp}}[[gram#SI multiples|mg]] of tryptophan to make 1{{nbsp}}mg of niacin. [[Riboflavin]], [[Vitamin B6|vitamin B<sub>6</sub>]] and [[iron]] are required for the process.<ref name=PKIN2020Niacin /> Pellagra is a consequence of a corn-dominant diet because the niacin in corn is poorly bioavailable and corn proteins are low in tryptophan compared to wheat and rice proteins.<ref name=Carpenter1983>{{cite book |doi=10.1007/978-3-0348-6540-1_12 |chapter=The Relationship of Pellagra to Corn and the Low Availability of Niacin in Cereals |title=Nutritional Adequacy, Nutrient Availability and Needs |series=Experientia Supplementum |year=1983 | vauthors = Carpenter KJ |volume=44 |pages=197–222 |pmid=6357846 |isbn=978-3-0348-6542-5 }}</ref>

===Industrial synthesis===
Nicotinic acid was first synthesized in 1867 by oxidative degradation of [[nicotine]] with [[potassium chromate]] and [[sulfuric acid]]<ref name=Ullmann2015/> — this is the origin of the name.<ref name=JAMA1942a>{{cite journal|title=Niacin and Nicotinic Acid|date=7 March 1942|volume=118|issue=10|doi=10.1001/jama.1942.02830100053014|journal=Journal of the American Medical Association|page=823}}</ref> Niacin is prepared by hydrolysis of [[nicotinonitrile]], which, as described above, is generated by oxidation of 3-picoline. Oxidation can be effected by air, but [[ammoxidation]] is more efficient. In the latter process, nicotinonitrile is produced by ammoxidation of [[3-methylpyridine]]. [[Nitrile hydratase]] is then used to catalyze nicotinonitrile to nicotinamide, which can be converted to niacin.<ref>{{Ullmann|vauthors=Abe N, Ichimura H, Kataoka T, Morishita S, Shimizu S, Shoji T, Watanabe N |year=2007 |doi=10.1002/14356007.a22_399|title=Pyridine and Pyridine Derivatives|isbn=978-3527306732}}</ref> Alternatively, ammonia, acetic acid and paraldehyde are used to make [[5-Ethyl-2-methyl-pyridine|5-ethyl-2-methyl-pyridine]], which is then oxidized to niacin.<ref name=LONZA>{{cite journal | vauthors = Eschenmooser W |title=100 Years of Progress with LONZA |journal=CHIMIA |date=June 1997 |volume=51 |issue=6 |pages=259–69 |doi=10.2533/chimia.1997.259 |s2cid=100485418 |doi-access=free }}</ref> New "greener" catalysts are being tested using manganese-substituted aluminophosphates that use acetyl peroxyborate as non-corrosive oxidant, avoiding producing nitrogen oxides as do traditional ammoxidations.<ref>{{cite journal| author = Sarah Everts| title = Clean Catalysis: Environmentally friendly synthesis of niacin generates less inorganic waste| journal = Chemical & Engineering News| year = 2008| issn = 0009-2347}}</ref>

The demand for commercial production includes for animal feed and for food fortification meant for human consumption. According to ''[[Ullmann's Encyclopedia of Industrial Chemistry]]'', worldwide 31,000 tons of nicotinamide were sold in 2014.<ref name=Ullmann2015>{{cite encyclopedia|encyclopedia = Ullmann's Encyclopedia of Industrial Chemistry|year = 2015|publisher = [[Wiley-VCH]]|location = Weinheim|isbn = 978-3-527-30385-4|edition = 6th|title = Vitamins, 11. Niacin (Nicotinic Acid, Nicotinamide|pages = 1–9| vauthors = Blum R |doi = 10.1002/14356007.o27_o14.pub2|chapter = Vitamins, 11. Niacin (Nicotinic Acid, Nicotinamide)}}</ref>

===Climate impact===
The production of niacin creates [[nitrous oxide]] as a by-product, which is a potent greenhouse gas. In 2018, it was discovered that a niacin factory in [[Visp]], Switzerland, was responsible for around one percent of the country's greenhouse gas emissions.<ref>{{cite web | vauthors = Lenz C | title = The climate disgrace of Visp | newspaper = European Press Prize | year = 2021 | url = https://www.europeanpressprize.com/article/the-climate-disgrace-of-visp/ | access-date = 8 September 2023 | archive-date = 8 September 2023 | archive-url = https://web.archive.org/web/20230908132352/https://www.europeanpressprize.com/article/the-climate-disgrace-of-visp/ | url-status = live }}</ref> Eventually, catalytic scrubbing technology that eliminates most of the emissions was installed in 2021.<ref>{{cite journal | vauthors = Davidson EA, Winiwarter W |title=Urgent abatement of industrial sources of nitrous oxide |journal=Nature Climate Change |date=July 2023 |volume=13 |issue=7 |pages=599–601 |doi=10.1038/s41558-023-01723-3|bibcode=2023NatCC..13..599D }}</ref>