Asian Scientist (Sep. 12, 2013) – The science behind the tingling sensation caused by eating Sichuan pepper, a popular Asian spice, has been uncovered by researchers.
The study, published in the Proceedings of the Royal Society B, helps shed light on the complex interactions between the senses of taste and touch, and could lead to a greater understanding of the causes of the tingling sensations experienced by many chronic pain patients.
Widely used in Asian cooking, Sichuan pepper was found to mimic the sense of touch in the brain. The researchers discovered that it chemically activates light-touch fibers on the lips and tongue, and sends the equivalent of a light tap on the skin to the brain at the rate of 50 times per second.
“This is the first time that we’ve been able to show how chemicals activate touch fibers, inducing a measureable frequency,” said Dr Nobuhiro Hagura, lead author of the study.
“We know that natural products like chili, mustard oil and menthol can activate the thermal and pain fibers in the skin, but we wanted to find out why Sichuan pepper specifically works on the light-touch fibers, producing a conscious sensation of touch and that distinctive tingling feeling.”
After Sichuan pepper was applied to the lips of volunteers, participants were asked to match the frequency of the resulting tingling sensation by adjusting a vibrating stimulus, either higher or lower, on their fingertips.
The team was able to show that an active ingredient in the peppers stimulates specific RA1 fibers, responsible for transmitting touch sensation, in the lips and tongue.
“What we found was that a unique active ingredient in the pepper, called sanshool, activates these fibers, sending a highly specific signal to the brain. Sichuan peppers and physical touch sensations share this same pathway to the brain,” said Dr Hagura.
“We hope that laboratory studies of the tingling sensations caused by sanshool could help to clarify the brain processes underlying these sensations, and how they are related to pain in some cases.”
The team also hopes to investigate the reasons why people enjoy eating Sichuan pepper and how touch sensation can boost the taste of food.
The article can be found at: Hagura et al. (2013) Food Vibrations: Asian Spice Sets Lips Trembling.
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Source: UCL; Photo: laogooli/Flickr/CC.
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