Garlic, like leeks and onions, belongs to the plant genus Allium, and is known for its pungency and spiciness.
In recent years, science has tentatively linked consumption of garlic to having a beneficial impact on the heart, including reducing blood pressure and cholesterol. But the molecular mechanisms underlying these effects remain unknown.
For this latest study, Swedish and US researchers demonstrated that the allicin molecule in garlic stimulated sensory pain neurons in rats by activating the TRPA1 channel.
The Allium family of plants produce organosulfur compounds, such as allicin and diallyl disulfide (DADS), which account for their pungency and spicy aroma.
"Intriguingly, allicin and DADS share structural similarities with allyl isothiocyanate, the pungent ingredient in wasabi and other mustard plants that induces pain and inflammation by activating TRPA1, an excitatory ion channel on primary sensory neurons of the pain pathway," reports study co-author David Julius, a professor of cellular and molecular pharmacology at the University of California, San Francisco.
Suggesting a tentative link to the reported health benefits of eating garlic, the scientists found that allicin and DADS induced vasodilation (the healthy enlargement of blood vessels), by activating "capsaicin-sensitive perivascular sensory nerve endings."
But still early days, research is now required in animals and humans to advance the test-tube findings.
Full details about the study are published in the August 15, 2005 issue of the Proceedings of the National Academy of Sciences.
Allicin is converted to a variety of more stable sulfide compounds over time or with heating, in correspondence with the significantly milder taste of roasted garlic. And this active compound is enjoying a certain growth, mostly in garlic supplements, on the back of the reported health benefits.
Garlic supplements are worth more than $100 million in the US. A garlic extract (supplied by UK firm Allimax) was recently added into the formulation of new product from US functional drinks company V-Net Beverage, thought to be the first time a garlic extract has been added to a functional food.