Happiness Exercise No. 1: The Joy of Bitter, or, How Sniffing Horseradish May Improve Mood

Reader Contribution by Ellen Sandbeck
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Researchers have recently discovered taste receptors in an unlikely location: deep in our bronchial tubes, in the smooth muscle that controls air flow into the lungs. There are no other types of functional taste receptors in the lungs, just bitter detectors. After this discovery, the obvious question was, “What the hell are taste receptors doing in the lungs?” And the obvious (but wrong) answer was that since a bitter taste is often an indicator of the presence of a toxin, that those bitter receptors in the lungs must trigger a “batten down the hatches” sort of response.

The bitter-taste receptors were discovered by accident, when researchers at the University of Maryland School of Medicine were studying the lung-muscle receptors that regulate airway contraction and relaxation; these are the same muscles that contract or tighten when an asthma sufferer is having an asthma attack. After the taste-receptors were discovered lurking in the lungs, the researchers exposed bitter-tasting compounds to human and mouse airways, to individual bronchial smooth muscle cells, and to asthmatic mice.

Professor Stephen Liggett, pulmonologist and the study’s senior author said: “I initially thought the bitter-taste receptors in the lungs would prompt a ‘fight or flight’ response to a noxious inhalant, causing chest tightness and coughing so you would leave the toxic environment, but that’s not what we found.” The research team tested a few standard bitter substances such as quinine and chloroquinine, and according to Dr. Liggett, “It turns out that the bitter compounds worked the opposite way from what we thought. They all opened the airway more profoundly than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease (COPD).”

The researchers found that administering bitter substance in an aerosolized form relaxed the airways of asthmatic mice, while eating bitter foods or compounds did nothing to relax mouse airways.

Previous research has shown that some molecules produced by bacteria trigger bitter receptors. Now researchers speculate that relaxed airways may prevent lung infections from festering: “When you get a lot of gunk in there it leads to a closed airway. That would have been fatal in the days before antibiotics,” said professor Liggett.

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