The biochemical function of nicotinic acid was discovered before the nutritional role of this compound was appreciated. Warburg et al., (1935) isolated nicotinic acid from their ”old yellow enzyme,” subsequently identified as NADP (nicotinamide-adenine dinucleotide phosphate), and showed that it was part of a cellular hydrogen transport system. Funk (1911) had previously isolated the compound in his search for the antipolyneuritis factor for the chick.
Niacin is essential in the diets of nonruminant species for the prevention of a variety of severe metabolic disorders of the skin, gastrointestinal tract, and other organs. The first signs of niacin deficiency in most species are loss of appetite, reduced growth, generalized muscular weakness, digestive disorders, and diarrhea. A scaly dermatitis and, often, a microcytic anemia follow these signs. These conditions are referred to as black tongue disease in dogs, pellagra in humans, and pig pellagra in swine. The niacin-deficient chick also shows an abnormality of leg development called perosis
