Research overview: niacin requirement and tryptophan metabolism in cats

Cats require dietary niacin because, although many animals can synthesize niacin from the amino acid tryptophan, cats divert tryptophan down a competing metabolic pathway so efficiently that little is available for niacin synthesis, leaving them dependent on preformed dietary niacin. This metabolic quirk again reflects the cat's adaptation to a meat-rich diet naturally high in B vitamins. This overview synthesizes the nutritional-biochemistry literature rather than one citation, describing why cats cannot meet their niacin needs from tryptophan, how this requirement is met in formulated diets, and what deficiency would entail. It matters because the niacin requirement adds to the catalog of feline nutritional peculiarities arising from carnivorous metabolism, each of which must be accounted for to produce diets that keep cats healthy.