Gut bacteria that helps to fight the flu works better if given antioxidant compounds found in red wine, black tea and blueberries, finds a study in mice.
The trillions of bacteria that live in your gut – known as the microbiome – don't just help with digestion. They also play a big role in mental health and in controlling body weight. Not least, they are also the masterminds of the immune system.
Now scientists at the University of Washington's School of Medicine have discovered that some of these bacteria do a much better job at fending off flu if they have an adequate supply of a type of antioxidant called flavonoids.
If the bacterium Clostridium orbiscindens was present in mice, and if the mice were given a diet high in flavonoids, they recovered from the flu much more quickly than control mice. The results are published in the journal Science.
"For years, flavonoids have been thought to have protective properties that help regulate the immune system to fight infections," said study author Ashley Steed 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."
But before reaching for the wine at the first sign of a cold, there are two things to consider. First, the study was done in mice, not humans. So further research would be needed before confirming this holds true for people too.
And secondly, the flavonoids alone are not enough. The mice had to have Clostridium orbiscindens present in their guts. If they didn't, the flavonoids couldn't work this way.
"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 Thaddeus Stappenbeck of the Conan Professor of Pathology & Immunology, also a study author.
The bacteria used the flavonoids to boost a molecule called interferon, which aids the immune response. They did this by breaking down the flavonoids into a compound called desaminotyrosine (DAT). This cut down the flu-related lung damage in the mice, which in humans can cause complications such as pneumonia.
"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," Stappenbeck said.
Next, the researchers hope to find more kinds of gut bacteria that could break down flavonoids in this way to boost the immune system. Until then, the researchers say that eating lots of blueberries and drinking black tea before the next flu season certainly isn't likely to hurt.