Drinking tea could be the key to keeping flu at bay, according to a new study.
Researchers discovered a gut microbe which helped prevent severe flu infections in mice, likely by breaking down naturally occurring compounds called flavonoids - commonly found in black tea, red wine and blueberries.
Influenza - characterised by a fever, cough and body aches - is a common and sometimes deadly viral infection of the upper respiratory tract.
Around the world, the World Health Organisation estimates there are between 250,000 and 500,000 flu-related deaths annually.
Previous evidence has suggested that microbes living in the gut may be important in protecting against severe flu, so in this study, the researchers aimed to identify which microbes might provide that protection.
“For years, flavonoids have been thought to have protective properties that help regulate the immune system to fight infections,” said lead author of the study, Ashley Steed, an instructor in paediatrics at St Louis Children’s Hospital.
“Flavonoids are common in our diets, so an important implication of our study is that it’s possible flavonoids work with gut microbes to protect us from flu and other viral infections. Obviously, we need to learn more, but our results are intriguing.”
As part of the study, scientists at Washington University School of Medicine in St Louis screened human gut microbes looking for one that metabolised flavonoids.
They identified one such microbe that they suspected might protect against flu damage, called Clostridium orbiscindens, which breaks down flavonoids to produce a metabolite that boosts the immune system.
“The metabolite is called desaminotyrosine, otherwise known as DAT,” Steed said. “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.”
Interestingly, although the lungs of DAT-treated mice didn’t have as much flu damage, their levels of viral infection were identical to those in mice that didn’t get the treatment.
“The infections were basically the same,” said study author Thaddeus Stappenbeck, the Conan Professor of Pathology and Immunology at Washington University School of Medicine in St Louis. “The microbes and DAT didn’t prevent the flu infection itself, the mice still had the virus. But the DAT kept the immune system from harming the lung tissue.”
That’s important because annual flu vaccines aren’t always effective at preventing infections, they said.
“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.”
Researchers said more studies are needed, but added it might not be a bad idea to drink black tea and eat foods rich in flavonoids before the next flu season begins.