Chinese people have exploited traditional foods through their long history, and developed an abundant food culture. Especially, preserving health by dieting has been an important part of the traditional food culture in China, which is based on the theory of Chinese medicine. Some of the traditional foods are on the verge of being lost, but improvements in traditional foods will benefit agricultural industries, especially those in poor regions. The theories of traditional Chinese healthy food need more systematic study based on modern science and technology. Some of the fermented soybean foods such as sufu and douchi were reported to contain functional materials. We found that isoflavones composition in the fermented food changed during fermentation, which was closely related to β-glucosidase activity. Through these researches, we can use the wisdom of healthy eating habits accumulated over the centuries as beneficial knowledge for the health of people.