Black Tea Flavonoids May Help Tame the Flu

Black tea in a cup and dried leaves

It is possible that flavonoids in black tea, red wine and blueberries work with gut microbes – those found in the digestive tract — to protect against flu and other viral infections.

Researchers at Washington University School of Medicine in St. Louis found that a particular gut microbe can prevent severe flu infections in mice, probably by breaking down flavonoids, according to a statement by the university.

“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,” said the study’s senior author, Dr. Thaddeus Stappenbeck, Conan Professor of Pathology & Immunology.

“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,” Stappenbeck said in the university’s statement.

Worldwide, influenza epidemics are estimated to result in about 3 to 5 million cases of severe illness and about 250, 000 to 500 000 deaths per year, according to the World Health Organization.

As part of the study, the researchers screened human gut microbes looking for any that metabolized flavonoids. They identified one they suspected might protect against flu damage. The microbe, called Clostridium orbiscindens, degrades flavonoids to produce a metabolite that enhances interferon signaling.

The metabolite is called desaminotyrosine, also known as DAT, Ashley L. Steed, an instructor in pediatrics who treats intensive care patients at St. Louis Children’s Hospital said in the statement. “When we gave DAT to mice and then infected them with influenza, the mice experienced far less lung damage than mice not treated with DAT.”

The lungs of DAT-treated mice didn’t have as much flu damage, but their levels of viral infection were identical to those in mice that did not get the treatment, according to the researchers. The microbes and DAT did not prevent the flu infection itself — the mice still had the virus — but the DAT kept the immune system from harming the lung tissue.

With DAT, “it may be possible to keep people from getting quite as sick if they do become infected,” Steed said. “This strategy doesn’t target the virus. Instead, it targets the immune response to the virus. That could be valuable because there are challenges with therapies and vaccines that target the virus due to changes in the influenza virus that occur over time.”

The study was published Aug. 4 in the journal Science.

Sources: Washington University School of Medicine in St. Louis, World Health Organization, Science