Excerpted from The Chile Pepper Encyclopedia (William Morrow & Co., 1999).
The sensation of heat created by capsaicin in chiles is caused by the irritation of the trigeminal cells, which are pain receptors located in the mouth, nose, and stomach. These sensory neurons release substance P, a neuropeptide chemical messenger that tells the brain about pain or skin inflammation. Repeated consumption of chile peppers depletes nerves of substance P, which is the reason people eventually build up a tolerance to capsaicin and can eat hotter and hotter foods.
When applied topically to treat skin pain, capsaicin “triggers a burst of the neuropeptide substance P from the C fibers,” according to the Journal of the American Medical Association, and this is what causes the initial burning sensation. Repeated use of capsaicin also prevents the nerve endings from making more substance P, and thus further pain signals from the skin are greatly diminished or completely eliminated as long as the capsaicin is applied. When the capsaicin treatment is concluded, the substance P stores revert to normal.
There is a great deal of confusion about the effects of capsaicin on the tongue and taste buds, starting with the notion that men who can eat the hottest peppers are somehow more masculine or “macho.” The truth is that capsaicin is not detected by the taste buds, but by capsaicin receptors. That story is told in the article here.
Generally speaking, people who love chiles claim that they enhance the tastes of other foods, while people who avoid fiery foods contend that chiles reduce or mask food flavors. In fact, it has long been rumored that the capsaicin in chile peppers damages or destroys the tastebuds; noted chef Julia Child once made such a claim. There have been numerous studies on the subject of capsaicin desensitization, which generally have people judge the intensity of the taste of salt or citric acid after the mouth is treated with varying strengths of a capsaicin solution.
Desensitization does occur, causing a decrease in both the taste and tactile sensations on the tongue, but this effect seems to be temporary and does not destroy the tastebuds.
In fact, one study done by Tracey Karrer and Linda Bartoshuk of the Yale University School of Medicine, reported that in the sour and bitter taste tests: “As subjects recovered from capsaicin desensitization, their responses were enhanced in some cases to values higher than the precondition.” This would seem to indicate that although capsaicin desensitizes the taste buds, tastes seem to be enhanced after recovery. They also noted: “Anecdotally, several subjects gave ratings that seemed to indicate that, after desensitization, they developed sensitivity to tactile components or taste components that they had previously not sensed.” However, an earlier study of theirs indicated that people who eat chiles every day are in a constant state of desensitization, and consequently have less of an ability to perceive tastes. Also, desensitization means more of a tolerance for capsaicin, so the same level of heat would not seem so hot to them.
Interestingly enough, there may be a methodology factor at work as well. In an experiment by Beverly Cowart of the Monell Chemical Senses Center, where the capsaicin was actually mixed with what was being tasted, “no reduction in perceived taste intensity, relative to the control condition, was observed.” Cowart noted that periodic rinses always cause desensitization where mixtures do not, leading her to conclude: “Much of the apparent masking of taste intensity in the presence of oral irritation is not directly related to the irritation level but is sensitive to procedural variation.” So typically, we are left with conflicting scientific studies.
Dr. Barry Green of the Monell Chemical Senses Center theorizes that the conflict may have something to do with cognitive psychology. In his experiments, some people where able to taste many flavors after eating chiles, but others were not. As there are holistic people and analytical people in the practice of medicine, he sees the same dichotomy in the world of food. Some people see fiery foods and think, “This is ridiculously hot–I can’t taste a thing,” while others use their analytical abilities and think, “This is great–I can taste all these incredibly strong flavors.” After all, no matter how scientific the experiment, taste is still subjective. Dr. Green noted: “The easiest explanation for why people like pain from their food is simply that it adds a whole new dimension to flavor.”
Cooling the Burn
Many substances have been proposed as an antidote in the mouth to the heat of chiles, including water, milk, sugar, bread, citrus fruits, beer, and other carbonated beverages. The theory is that such substances can either wash away or dilute the capsaicin, or, like the bread, can absorb it. The problem is that the capsaicin is bound to the nerve receptor sites in the mouth and is not easily dislodged or diluted. Remember that capsaicin is very miscible with alcohol, fats, and oils, but not very miscible with water.
In a 1990 study at the University of California, Davis, Christina Wu Nasrawi and Rose Marie Pangborn reported that a ten percent sucrose solution at 20 degrees C. was just as effective as milk at 5 degrees C. A 5 percent ethanol solution was no more effective than water at cutting the burn. However, the effectiveness of sugar in warm water revives folk tales of it being an Asian cure for a chile overdose in the mouth. Richard Sterling, once the travel editor of Fiery Foods & Barbecue Magazine, wrote to us that a waiter in Pattaya Beach, Thailand, once dropped a cube of sugar into Richard’s too hot Dom Yom, or spicy prawn soup. The heat level dropped noticeably and then Richard observed that the condiment trays in Thai restaurants often include a small jar of sugar.
During a search to verify the ultimate cure for heat in 1989, the late John Riley, editor-publisher of the quarterly journal Solanaceae, tested various remedies reputed to remove the heat of the capsaicin in chile peppers. In each test, a slice of serrano chile was chewed for one minute, and then one of the following remedies was applied. The amount of time until the burning sensation eased was measured and the results were recorded.
Remedy Total Minutes
Rinse the mouth with water only 11
Rinse the mouth with one Tablespoon olive oil 10
Drink one-half cup heavy fruit syrup 10
Rinse mouth with one tablespoon Glycerine 8
Drink one-half cup milk, rinsing well 7
Milk was the winner, and indeed, dairy products have long been reputed to be the best cool-downs for the burning effects of capsaicin in chiles. But why?
Scientists now believe that casein in the milk is responsible for its cooling effects. According to Robert Henkin of The Taste and Smell Clinic in Washington, D.C., casein is a phosphoprotein that acts as a detergent and strips the capsaicin from the nerve receptor binding sites in the mouth which are contained in the taste papilli. The casein in milk is in the form of calcium caseinate, which constitutes about three percent of milk. Other possible cool-downs containing casein include milk chocolate and some beans and nuts.