Male Sprague Dawley rats received various amounts of extract of Crassostrea gigas by gavage every day for 2 weeks or one month. At these times, groups of animals were sacrificed and samples of major organs analyzed for levels of glutathione (GSH) and glutathione S-transferase (GST) activities. Following the two week protocol, GSH levels were significantly increased in the mucosa of the large intestine; at one month the small intestine and spleen were elevated. GST activity increased in liver under both schedules and at one month, activity was also elevated in kidney and small intestine. Since the Crassostrea gigas extract contains high levels of a variety of important amino acids, it is concluded that biologically available peptides are taken up in target organs and stimulate GSH metabolism. Enhanced levels of GSH and associated enzymes may contribute to a more effective detoxification phenotype, thus providing enhanced chemoprotective capacity.