The functional effects of Japanese style fermented soy sauce (shoyu) have been studied. Soy
sauce promotes digestion, because the consumption of a cup of clear soup containing soy sauce enhances
gastric juice secretion in humans. Soy sauce possesses antimicrobial activity against bacteria
such as Staphylococcus aureus, Shigella flexneri, Vibrio cholera, Salmonella enteritidis, nonpathogenic
Escherichia coli and pathogenic E. coli O157:H7. Soy sauce also contains an antihypertensive
component. An angiotensin I-converting enzyme inhibitor having antihypertensive
effects was found in soy sauce. The active compound was identified as nicotianamine, which
comes from soybeans. Soy sauce exhibits anticarcinogenic effects. Giving diets containing soy
sauce to mice inhibit benzo[a]pyrene (BP)-induced forestomach neoplasia