An additive in many common foods may worsen people’s flu, scientists have found.

The little-known antioxidant, which is found in products such as frozen and dehydrated meat and processed food, suppresses the body’s immune response to infection, the experts say.

The additive, tertiary butylhydroquinone (TBHQ), also known as E319, not only increases the severity of flu symptoms, but may also reduce the effectiveness of the flu vaccine, according to the US researchers.

They believe the link may help explain why flu worldwide has not been eradicated, Eureka Alert reported.

E319, which is banned in some countries including Japan, is most common in high-fat foods, for which it is used as a preservative.

Creative vegan dishes from YouTubers - In pictures Show all 15 1 /15 Creative vegan dishes from YouTubers - In pictures Creative vegan dishes from YouTubers - In pictures Vegan naked chicken chalupa Creative vegan dishes from YouTubers - In pictures Easy vegan brownie bites Creative vegan dishes from YouTubers - In pictures Maple peach pecan overnight oats Creative vegan dishes from YouTubers - In pictures Macaroni skillet Creative vegan dishes from YouTubers - In pictures Cauliflower buffalo wings Creative vegan dishes from YouTubers - In pictures Vegan animal style fries Creative vegan dishes from YouTubers - In pictures Cheese Brussels sprouts tots Creative vegan dishes from YouTubers - In pictures Vegan beer and cheddar bread bowl dip Creative vegan dishes from YouTubers - In pictures Vegan s'more tacos Creative vegan dishes from YouTubers - In pictures Vegan chicken ceasar wraps Creative vegan dishes from YouTubers - In pictures Caramelised onion dip Creative vegan dishes from YouTubers - In pictures Tortilla soup and cheesy taquitos Creative vegan dishes from YouTubers - In pictures Easy vegan chilli Creative vegan dishes from YouTubers - In pictures Vegan chocolate hazenlut tarts Creative vegan dishes from YouTubers - In pictures Cassava bacon

Snack manufacturers in the UK said the only snacks they were aware of on the UK market containing TBHQ were a few products from the US and South Africa, and the “minimal” additive was a listed ingredient.

In Europe, it is allowed in milk powder for vending machines; fats and oils for processed heat-treated foods; frying oil and lard, fish oil, beef, poultry and sheep fat; frying fat; processed nuts, nut butters and spreads; dehydrated potatoes; cake mixes; heat-processed dehydrated meat; dehydrated soups and cereal-based snacks.

But it’s believed in many cases the amounts involved are barely perceptible.

“If you get a vaccine, but part of the immune system doesn’t learn to recognise and fight off virus-infected cells, then this can cause the vaccine to be less effective,” said Robert Freeborn, a PhD student at Michigan State University.

“Our studies showed that mice on a TBHQ diet had a weakened immune response to influenza infection. In our mouse model, TBHQ suppressed the function of two types of T cells, helper and killer T cells. Ultimately, this led to more severe symptoms during a subsequent influenza infection.”

T cells are involved in the immune response to a variety of diseases, so TBHQ could also play a role in other infectious diseases, Mr Freeborn added.

The World Health Organization says a flu pandemic is only a matter of time.

TBHQ, which is derived from petrol and is also used as a varnish, seems to impair the vaccine’s memory of how to fight off a virus, he said.

It is more commonly found in food in the US, where it can be in frozen fish, ice cream, microwave popcorn and chicken nuggets.

Support free-thinking journalism and attend Independent events

Mr Freeborn said the best way to avoid it was by having a low-fat diet and cutting down on processed snacks.