Tofuyo (fermented soybean food) extract prolongs the survival of mice infected with influenza virus.

Fermented soybean, known as tofuyo, is a traditional food in Okinawa (Japan). Tofuyo extract is obtained from the supernatant of fermented soybean after homogenization, filtration and centrifugation. In this study, we analyzed the in vitro effect of tofuyo extract on influenza virus using immunochromatography of the influenza virus nucleoprotein (NP). The results showed that tofuyo extract does not have a strong inhibitory effect on NP. This finding was confirmed by an assay for virus activity using embryonated eggs. To investigate the potential anti-influenza virus activity of tofuyo in vivo, 5 nude mice (BALB/cSlc-nu/nu) were administered drinking water supplemented with tofuyo extract the day prior to intranasal inoculation with influenza virus, while the control group (5 mice) was administered tofuyo extract-free water. Control group mice (40%) were dead within 14 days, while the mice that were administered water containing tofuyo extract survived. Nutrient component analysis showed that tofuyo extract contains proteins, carbohydrates, vitamins and minerals that provide nutritional value, which may help to maintain good health.