Black tongue is the disease described by American veterinarians as having syndrome and condition comparable to human pellagra. Although Elvehjem et al. were the first to identify the curative factors for black tongue in dogs, they were not the first to isolate these factors. Nicotinamide is a component of coenzyme II. It was first isolated in 1934 by Otto Warburg and Walter Christian in Germany (Roe, 1973), during the course of their studying the physiological significance of vitamins. Nicotinic acid, on the other hand, was first isolated from rice polishings in 1911 by Casimir Funk in London (Williams, 1973). Niacin is the official vitamin name for nicotinic acid, which is easily converted to its amide form, nicotinamide. When subsequent treatments of pellagrins with nicotinamide or nicotinic acid were seen successful, these compounds were firmly confirmed as the pellagra-preventive factor.

Biochemical understanding about niacin being the pellagra-preventive factor has a great impact on disease prevention. For example, milk has the ability to prevent pellagra although it is low in niacin. As pointed out by Williams (1973), milk prevents and cures pellagra because it is high in the essential amino acid tryptophan. As mentioned earlier (Slide 6), tryptophan is a precursor of niacin, a fact discovered in 1945 by Willard Krehl’s group at the University of Wisconsin (Krehl et al., 1945a, 1945b).