A preservative commonly used to increase the shelf life of food products may weaken the body’s immune defense against influenza, according to scientists from Michigan State University.
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The team found that when vaccinated mice were given food containing tert-butylhydroquinone (tBHQ), they took three days longer to fight off the flu, compared with mice that were not given the preservative.
The findings, which have not yet been published, were recently presented at the American Society for Pharmacology and Experimental Therapeutics annual meeting in Orlando, Florida.
The tBHQ additive is an aromatic organic compound that helps to stabilize animal fats and unsaturated vegetable oils. It has previously been linked to a rise in food allergies.
Food manufacturers often use it to increase the shelf-life of products ranging from frozen meats to cooking oils, crackers and fried foods. However, these companies are not required to list the ingredient on food packaging, so it is unclear how much of tBHQ people are exposed to and “hard to know everything it’s in,” says study author Robert Freeborn.
The researchers found that tBHQ exposure appeared to make the flu vaccine less effective by suppressing the function of T cells, helper and killer T cells, thereby increasing the likelihood of infection fully setting in and more severe symptoms developing.
Furthermore, when the team later re-infected the animals with a different, but related flu strain, those that were fed a tBHQ diet suffered a longer-lasting illness.
This suggests that tBHQ impaired the immune system’s "memory response" that usually fights off a second infection. Given that this memory response is key to how a vaccine works, its impairment could potentially make the influenza vaccine less effective.
Scientists say the findings may help explain why seasonal flu continues to pose a such a major health threat, killing an estimated 290,000-650,000 people globally each year.
However, Freeborn stresses how important it is that people still protect against the flu by ensuring they receive a yearly flu shot; although people can still contract the infection following the shot, vaccination significantly decreases the severity and length of infection.
Next, the team plans to build on the findings by using blood samples taken from humans to further investigate the effects that tBHQ exerts on T cell activity.