Kicking It Up a Notch: How Some Spices Trick the Brain

When the chili pepper was first exported from Mexico about 500 years ago, it was an overnight success. Fiery-hot peppers were quickly adopted all over Asia, West Africa, and elsewhere around the world. Rather than avoiding a food that burns, people wanted more.

“It’s odd that something that tasted ‘bad’ would be so readily adopted,” says Paul Rozin, a professor of psychology at the University of Pennsylvania who has been studying spicy foods for decades. Through conditioning, people have grown to like other foods they once disliked. Coffee is bitter, but it has a pleasant aroma and stimulating effects. It’s also addictive. Jalapenos, habaneros, and other chilies, however, are not addictive — they merely burn.

Spicy foods fascinate because they have “impact,” according to Rozin. Even a touch of spice can add novelty and excitement to a meal. Ask anyone who has tasted the scorching heat of wasabi. Yet what causes the curious sensations triggered by certain spices? Is there any benefit to eating food that burns?

Deceiving The Brain

The five basic tastes — sweet, salty, bitter, savory, and sour — ensure our survival. Receptors on the taste buds send messages to the brain along nerve fibers to create the sensation of taste. Yet, the taste buds alone do not produce “taste.” The tongue also has receptors for temperature (and pain and pressure). Certain chemicals trigger receptors for other senses, mimicking temperature or touch, for instance, and contributing to what we experience as taste.

One food that deceives the mind is the Szechuan peppercorn. The tiny pods are often added to Mapo tofu and other dishes. The Szechuan peppercorn causes a peculiar tingling sensation that numbs the lips and mouth. It has an electrifying taste that often surprises and even unsettles people who try it for the first time.

The numbing spiciness of the Szechuan peppercorn is due to a compound called “sanshool” that is also found in the Japanese sansho. Sanshool confuses the senses by simultaneously acting on different types of nerve endings, activating receptors that are sensitive to cold and touch. Some people compare the buzzing sensation to touching a nine-volt battery. The unique appeal of sanshool could be its mimicry of touch.

Neuroscientists have tested whether people experience the buzzing effects in the same way when they eat Szechuan peppercorns. The study, titled “Food vibrations: Asian spice sets tips trembling,” was published in the journal Proceedings of the Royal Society. Researchers asked 28 participants to compare the tingling sensation caused by sanshool to vibrations produced by a mechanical device placed on their fingertips.

After sanshool extract was applied to their lips, they selected the frequency of mechanical vibrations that matched the buzzing sensation, which was about 50 megahertz — the same frequency belonging to a certain type of nerve that transmits the sensation of touch. They concluded that the chemical compounds in Szechuan peppercorns act on touch fibers, sharing the same pathway as physical touch.

“This is the first time that we’ve been able to show how chemicals activate touch fibers, inducing a measurable frequency,” said the lead author of the study, Dr. Nobuhiro Hagura. The study was too small to draw any conclusions. Yet, it adds to research on how the brain processes sensory information. Scientists hope such findings could help improve our understanding of neurological conditions like chronic pain.

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