Eating These Foods May Help You Fight the Flu This Season

Nearly 2,000 years ago, Hippocrates, the father of modern medicine, said “all disease begins in the gut.” He may have overstated this a bit, but there is science supporting the notion that the gut microbiome—the entire universe of microbes, both good and bad organisms, that live in the gut—may be linked with overall health, including susceptibility or resistance to various diseases.

Even without thinking about the microbes that live in our gut, it seems that certain foods may help boost our immune systems. A study out of the Medical School at Washington University in St. Louis, suggests that at least one of the microbes that lives in our guts relies on certain foods we eat to boost our immunity. Specifically, in the 2017 study published in Science, researchers found that one particular gut microbe (Clostridium orbiscindens) prevented severe flu infections in mice, most likely by breaking down compounds called flavonoids that are commonly found in certain foods, including black tea, red wine, and blueberries.

The researchers knew beforehand that these compounds have immune-boosting properties. They also knew that the gut microbiome is important in protecting against influenza—a common infection of the upper respiratory tract that can cause serious and even deadly complications, particularly in older adults, pregnant women, young children, and those with certain chronic health problems, such as asthma and heart disease. Almost every winter in the U.S., human influenza A and B viruses cause seasonal epidemics of the disease, according to the Centers for Disease Control and Prevention.

In the study, the researchers decided to isolate and screen human gut microbes to find one that metabolized flavonoids. They discovered that Clostridium orbiscindens produces a metabolite that enhances interferon signaling (interferon signaling aids the body’s immune response). “The metabolite is called desaminotyrosine, otherwise known as DAT,” said first author Ashley M. Steed, MD, PhD. “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 immune response did not prevent, but rather minimized the damage caused by the virus. This is important since the influenza virus is constantly changing, and not all infections are preventable through vaccination. Influenza prevention requires a yearly vaccine to offer some level of protection for the current season.

Dr. Steed and her colleagues said the next steps include identifying other gut microbes that may use flavonoids to influence the immune system. In addition, it will be useful to explore ways of boosting levels of the bacteria in people whose intestines aren’t adequately colonized by Clostridium orbiscindens. It’s important to note that results of animal studies can’t always be translated to humans.

In the meantime, the authors suggest “it might not be a bad idea to drink black tea and eat foods rich in flavonoids before the next flu season begins.” Here are some ways that doctors avoid catching colds and flu. Already sick? Here’s how you can tell the difference between a cold and the flu.