Nonnutritive natural food components of important toxicological relevance. Favism, a disease caused by the ingestion of fava beans, is characterized by acute hemolysis, in serious cases accompanied by jaundice and hemoglobinuria. It is mainly found in Mediterranean populations with a congenital deficiency of NADPH-dependent glucose-6-phosphate dehydrogenase (G6PD). Fava beans contain two pyrimidine glycosides that have been shown to induce hemolysis: vicine and convicine. The aglycons are divicine and isouramil. Divicine and isouramil are powerful reducing agents. In red cells, they are readily oxidized by oxyhemoglobin to form methemoglobin, H2O2, and Heinz bodies (thought to consist of denaturated hemoglobin). The oxidation products undergo reduction by glutathione, and H2O2 is reduced by glutathione per¬ oxidase. The oxidized glutathione produced by these reactions is reduced by NADPH, generated from glucose-6-phosphate and G6PD. The defect leading to hemolysis lies in the red cells that have insufficient G6PD, that is, diminished levels of reduced glutathione, to protect them against oxidative attack.