Scientists have discovered a keen sense of taste boosts immunity – a breakthrough that could lead to nasal sprays to ward off illness.

People who find some vegetables, such as sprouts and broccoli, unbearably bitter are better at fighting off bugs due to chemicals in their nose, a study shows.

Experiments found they have more receptors that pick up the flavor of these foods – and also work as an early warning system about bacterial invaders.

They were traditionally thought to be located only on the tongue but are now known to be in the linings of the nasal and sinus cavities as well.

And these receptors are involved in activating the body’s natural defences against common infections.

However, almost a third of the population do not have the specific version of the bitter taste receptor gene called TAS2R38 that activates an immune response.

Dr. Noam Cohen, of the University of Pennsylvania in the United States, said: “If you are a supertaster, it is going to be very rare you are going to get sinusitis.”

But he added this bitter-tasting ability does not protect against all infections.

The findings, published in the Journal of Clinical Investigation, could lead to better treatments for chronic rinosinusitis, a condition of constantly inflamed and swollen sinuses which affects up to one in ten people.

Bitterness is the most sensitive of the tastes, and many find it unpleasant, sharp or disagreeable.

Common bitter foods also include marmalade, olives, citrus peel and wild chicory.

In the study the researchers grew cells in lab dishes, forming structures that resembled the multilayered lining of the nose and sinus, to test out how bitter receptors affect the initial stages of the infection process.

Chemicals produced by common bacteria called Pseudomonas aeruginosa activated the TAS2R38 bitter receptor, and caused the hair-like cilia that line the sinuses to start sweeping away microbial intruders.

The activation also resulted in the release into the sinuses of nitric oxide which kills bacteria.

The researchers looked at just one of 25 bitter receptors and it remains to be seen if the others affect the immune system.

In the past researchers have used phenylthiocarbamide (PTC) to identify people with functional bitter receptors.

Those who can taste the chemical are classified as supertasters,

The researchers said people who would say Brussel sprouts taste bitter are likely to be supertasters, having responsive bitter receptors.

The study also suggests supertasters may have a higher risk of chronic sinusitis, and that non-tasters have more upper respiratory infections.

Upon testing nasal tissue samples from patients who had undergone surgery related to sinus problems, the researchers found none of the eleven supertasters had Pseudomonas bacteria in their tissues, whereas seven out of twenty non-tasters had infections.

Dr. Thomas Finger, an expert in taste and smell at the University of Colorado, reviewed the research and said it could lead to an almost cost free test to distinguish supertasters from the more susceptible non-tasters.

He said certain bitter compounds could also be used to activate the immune system.

For example, a bitter nasal spray could be used to ward off an infection in the early stages.

But such potential therapies are a long way off.

Dr. Noam Cohen said his researchers will next look at whether genetics plays a role in people’s responses to sinusitis treatments.