Effects of Miso (Soybean Paste) on Postprandial Blood Sugar Levels

Abstract

The purpose of our study is to examine the possible postprandial blood sugar control effects of various kinds of miso (fermented soybean paste), a traditional Japanese seasoning, from the viewpoint of preventing diabetes mellitus. We examined the relationship between intake of each type of miso and postprandial blood sugar levels in a human intervention trial. Glycemic index (GI) following cooked polished rice intake, in vitro effects of miso on digestive enzyme (α-amylase and α-glucosidase) activities, and the relationship of brown color degree to the postprandial blood sugar control were examined. Based on a previous report indicating that the intake of trypsin inhibitor (TI), a component of soybean as raw material, promotes insulin secretion from pancreas, we examined TI content in miso. Some kinds of miso were suggested to reduce GI. In vitro, all kinds of miso inhibited the activities of various digestive enzymes (α-amylase, α-glucosidase and trypsin) to varied extent, and a small amount of TI was detected in the miso. Also the greater the color intensity due to the brown pigment of miso, the more strongly that trypsin was inhibited. Therefore, GI was considered to be controlled several factors. Our findings suggest that postprandial blood sugar rise can possibly be controlled to a certain extent by the intake of miso, and miso may be a food that can be used to prevent diabetes in the future