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Garlic's Punch May Inspire New Pain Drugs

L. Peat O'Neil
for National Geographic News
September 14, 2005
 
Garlic has been cultivated for at least 5,000 years. And while some cooks add it by the garland, others shy away from it like culinary vampires.

One explanation may simmer among the findings of scientists at the Scripps Research Institute in La Jolla, California. Scientists there are investigating why garlic tastes the way it does and how it affects the human body.

In a study recently published in the journal Current Biology, Scripps's Ardem Patapoutian and Lindsey Macpherson found that allicin, a chemical found in all raw garlic, triggers pain-sensing neurons in our mouths.

"Our study focused on [the] 'sensory' aspect of garlic," Patapoutian said, noting that a number of us "enjoy raw garlic—despite its potent ability to activate pain neurons."

Why? One theory "is that [garlic] causes 'pleasant pain,' a predictable pain that we have discovered to be nondamaging," Patapoutian said.

"Another theory is that activation of these pain neurons causes hypersensitivity in the mouth, so that other sensory/taste stimuli are enjoyed at more intense levels." In other words, garlic makes other flavors taste stronger.

The Scripps researches say the way garlic triggers pain sensations in our bodies may present a new avenue for drug research.

Hot Lily

A member of the lily family, garlic (Allium sativum L.) is a perennial subject of scientific research, with more than 3,000 scientific articles published on its chemistry, pharmacology, toxicology, and medicinal uses.

Many claims have been made about garlic's health benefits, including its ability to relax blood vessels and lower blood pressure.

In a study published last month, a team of U.S. and Swedish scientists found that garlic, chili peppers, and mustard plants excite pain-sensory neurons, or nerve cells, in the same way.

The researchers—based at the University of California, San Francisco and Sweden's Lund University—describe their study in the August 15 issue of the Proceedings of the National Academy of Sciences.

They found that garlic extracts stimulate neurons in rats by activating a pain receptor called TRPA1. In the human body TRPA1, a cell-membrane gateway, senses harmful stimuli.

The pain neurons, in turn, release brain chemicals that cause blood vessels to dilate and inflame.

"TRPA1 is also present on nerve endings in blood vessels and its activation leads to vasodilatation, which is an important component in inflammation," said study co-author Edward Högestätt. "Thus our findings may help to develop drugs acting on TRPA1 for treatment of pain and inflammation."

Compounds in chili peppers and in mustard plants also trigger the TRPA1 pain receptor. Scientists speculate that all three plants may have developed similar chemical irritants during their evolution.

The findings may shed a little light on the neurochemistry behind good cooking.

"Together with taste and smell, oral sensation of pain play[s] an important role in determining food flavor," Högestätt said. "Thus, targeting TRPA1 with pungent spices like mustard, wasabi, and garlic may contribute to successful cooking."

"It's Chic to Reek"

But you don't need a Ph.D. to appreciate the punch garlic packs in the kitchen.

Gene Sakahara, past president of the garlic festival in Gilroy, California, appears as a celebrity chef at the event's Great Garlic Cook-Off.

In an e-mail interview, Sakahara compared the taste of garlic, chili, and wasabi, which is made with mustard plant. "Raw garlic has a hotter flavor. But as a cooked herb, it becomes sweeter and [a] flavorful adding to any gourmet dish," he said. "Chili, as it simmers, takes on a hotter taste and pleases those who like hot and spicy foods."

"Wasabi, by itself, has the initial nasal rush, then adds to the flavor of the sushi," he said. "Of course, my favorite is still garlic. It's chic to reek."

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