Niacin Vitamers and Nomenclature

The term niacin is the generic descriptor for the two compounds that have the biological action of the vitamin nicotinic acid tuid nicotinamide (see 

Nicotinic acid was discovered and named tis a product of the chemictd oxidation of nicotine in 1867. When it was later discovered to be the pellagrapreventing viteimin, it was not assigned a number among the B vitcimins because its chemistry was already known. Niacin is generally placed between vitamins B2 and Be, altbougb it is incorrect to call it vitamin B3, wbicb was at one time assigned to pantotbenic acid (Section 12.1). 

There is confusion in tbe literature because of tbe North American usage of the name niacin to mean specifically nicotinic acid, whereas the amide is known as niacinamide. The name niacin was coined in the late 1940s when the role of deficiency in the etiology of pellagra was realized, and it was decided that dietcuy staples should be fortified with the vitamin. It was felt that nicotinic acid was not a suitable name for a substance that was to be added to foods, both because of its phonetic (and chemical) relationship to nicotine and because it is an acid. 

Nicotinic acid and nicotinamide have equal biological activity. As discussed in Section 8.3, approximately 60 mg of tryptophan is equivtdent to 1 mg of 

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