Tumorigenicity study of l-theanine administrated orally to mice

l-Theanine was orally administered at a concentration of 0–5% (maximum tolerated dose) of the diet to B6C3F1 mice for 13 weeks in a subacute test and 78 consecutive weeks, in a chronic toxicity test. There were no significant differences in intake of diet, weight gains or survival rates between treated and control groups. Unignorable differences in tumor incidence were observed at the end of 78 weeks; however, total number of tumors decreased significantly in the l-theanine administered groups. Thus, the long-term oral administration of l-theanine to mice did not show any chronic toxicological evidence or tumorigenic aberration.