Abstract
The ketone bodies, acetoacetate and β-hydroxybutyrate, when admistered to niacindeficient rats along with tryptophan, inhibited the synthesis of niacin from tryptophan. Prolonged administration of the ketone bodies to rats on normal diet, induced a metabolic defect, which inhibited the synthesis of niacin from administered trypotophan. Administration of acetoacetate and β-hydroxybroxybutyrate for seventy-five days considerably decreased the niacin contents of blood, liver and muscle.