From Longman Dictionary of Contemporary Englishniacinni‧a‧cin /ˈnaɪəsɪn/ noun [uncountable] a type of vitamin that is good for your skin and your nervous system
Examples from the Corpus
niacin• Untreated maize is reluctant to give up its B vitamins, particularly its niacin.Origin niacin (1900-2000) nicotine + acid + -in chemical compound 