Nutrition education is a very important tool for the promotion of human health. Epidemiological studies showed a strong association between postprandial glycemia and the cardiovascular risk. White rice is the staple food in Japan, but it is a high glycemic index diet. In our study, postprandial glucose levels were suppressed when viscous meals and barley were used as the side dishes and staple food with average-sized portions, respectively. Thus, information on the association between the traditional Japanese diet and health is still quite limited at this point. In conclusion, further human studies on food function are required in order to provide the public with accurate information.