We investigated the effects of allyl isothiocyanate (AITC) on the blood glucose levels of mice using an intraperitoneal glucose tolerance test. The intragastric administration of 25 mg/kg body weight AITC reduced the increase in blood glucose level after 2 g/kg body weight glucose was given intraperitoneally, compared with that of control mice. To elucidate the mechanism responsible for the reduction, respiratory gas analysis employing (13)C-labeled glucose was performed. The intragastrically administering AITC increased (13)CO2 emission, compared to vehicle, after intraperitoneal administration of (13)C-labeled glucose. This indicated that AITC increased the utilization of exogenously administered glucose, which was excessive glucose in the blood. To examine whether transient receptor potential (TRP) channels mediated this reduction in the blood glucose levels, we used TRPA1 and TRPV1 knockout (KO) mice. Intragastrically administering AITC reduced the increase in the blood glucose level in TRPA1 KO mice but not in TRPV1 KO mice. These findings suggest that dietary AITC might reduce the increases in blood glucose levels by increasing the utilization of excessive glucose in the blood by activating TRPV1.