Shinshu University and Asahimatsu Foods joint study finds Koya-dofu helps prevent obesity

Researchers have discovered that koya-dofu, made by freezing, aging, and drying tofu, has functions that help prevent obesity and fatty liver. A research team led by Professor Naoki Tanaka from the International Relations Office of Shinshu University School of Medicine and Graduate School of Medicine, Science and Technology, along with Director Takahiro Ishiguro of the Asahimatsu Foods Food Research Laboratory, revealed that protein derived from koya-dofu and resistant protein abundantly contained in koya-dofu reduce weight gain and fatty liver in mice fed a high-fat diet. Incorporating koya-dofu effectively into one's diet may help prevent obesity and fatty liver, which have been increasing in recent years. These findings were published in the International Journal of Biological Macromolecules.

The Shinshu region has long been known for its thriving production of koya-dofu, with nearly 100% of koya-dofu (also called kori-tofu or shimi-dofu) being produced in Nagano Prefecture. While small-scale studies have reported that koya-dofu, which is rich in resistant protein, lowers post-meal blood glucose and blood lipids, the effects of koya-dofu on metabolism and its mechanisms were completely unknown. In this study, the research team examined whether protein and resistant protein obtained from koya-dofu could prevent obesity in mice fed a high-fat diet.

When mice were fed a normal diet and a high-fat diet for 16 weeks respectively, mice fed the high-fat diet gained significantly more weight and developed more fatty liver compared with those on the normal diet. However, when protein derived from koya-dofu or resistant protein was mixed into the high-fat diet and fed to mice in the same manner, weight gain and the severity of fatty liver were reduced. When protein derived from koya-dofu was consumed, intestinal bacteria responded and azelaic acid in the intestines increased. This increased GLP-1 production in the ileum, with the GLP-1 then reaching adipose tissue and the liver and promoting fat burning. This is thought to be the mechanism by which koya-dofu-derived protein reduces weight gain and fatty liver. No adverse effects on the stomach, kidneys, heart, or other organs were observed from koya-dofu protein or resistant protein.

Modern diets tend to be biased toward foods high in fat and carbohydrates, and the increase in obesity and fatty liver has become a global problem. Consuming koya-dofu protein together with meals may reduce weight gain and fatty liver. Based on the findings obtained from this research, Shinshu University aims to collaborate with Asahimatsu Foods and explore the potential of koya-dofu for extending healthy life expectancy, and to contribute to the prevention of obesity and lifestyle-related diseases.

Journal Information
Publication: International Journal of Biological Macromolecules
Title: Kori-tofu ameliorates obesity and steatotic liver disease through enhancing GLP-1 production in the ileum
DOI: 10.1016/j.ijbiomac.2025.149537
PMID: 41360246