It is quite possible that the flavonoids found in black tea, red wine and blueberries work in conjunction with gut microbes found in the digestive tract to protect against flu and other viral infections.
Washington University School of Medicine in St. Louis found in a study that a particular gut microbe can prevent severe flu infections in mice, probably by breaking down flavonoids, according to a statement by the university.
According to the study’s senior author, Dr. Thaddeus Stappenbeck, Conan Professor of Pathology & Immunology, “It’s not only having a diet rich in flavonoids, our results show you also need the right microbes in the intestine to use those flavonoids to control the immune response.”
In the university's statement Stappenbeck said, “We were able to identify at least one type of bacteria that uses these dietary compounds to boost interferon, a signaling molecule that aids the immune response. This prevented influenza-related lung damage in the mice. It is this kind of damage that often causes significant complications such as pneumonia in people.”