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Photo of Linda Bartoshuk Linda Bartoshuk as seen on
Life's Little Questions: Why Are Peppers Hot?

Click on Linda's photo to read a brief bio.



q If you eat too many peppers can you lose your sense of taste? (Seems like this is what happened to Alan Alda while he was tasting foods at the chili food festival.) Will your sense of taste return? How long will it take to return? Lauren

A Fortunately for all of us who love chili peppers, exposing the tongue to capsaicin does not affect the sense of taste in the long run. However, while you are experiencing the burn of the pepper, you may notice that tastes seem blunted (e.g., see Lawless, Rozin, and Shenker, 1985). The exact mechanism for this effect is not known. Dr. Tracy Karrer (one of my students) studied desensitization of the tongue to capsaicin. She asked subjects to swab capsaicin solutions onto their tongues for 15 minutes. Then she let the burn of the capsaicin slowly fade (it takes about 20 minutes). After that when she reapplied capsaicin, it produced no burn (this is an example of the desensitization of the tongue that can be used to treat the pain of oral lesions); however, the only taste change was a slight reduction in the ability to taste bitter and that lasted on the order of days. References:
Karrer, T. and Bartoshuk, L.M. (1995) Effects of capsaicin desensitization on taste in humans. Physiology and Behavior, 57:421-429.

Lawless, H., Rozin, P. and Shenker, J. (1985) Effects of oral capsaicin on gustatory, olfactory, and irritant sensations and flavor identification in humans who regularly or rarely consume chili pepper. Chemical Senses, 10:579-589.




q When eating peppers of different strengths, one starts getting very hot physically in different levels. This energy is coming from the body itself and was triggered by molecules in the pepper? Steffan

A When we eat peppers, there is a normal reaction called, "gustatory sweating." Typically, the sweating is restricted to the head. The classic account of this phenomenon is given in a paper by T.S. Lee (1954). Lee asked 25 subjects to chew a chili for 5 minutes and 24 of them experienced sweating on various regions of the face and scalp. He went on to note, "In every subject, including the subject who did not sweat, there was an immediate flushing of the face and reddening of the conjunctivae on chewing chillies. The flushing usually extended to the chest and shoulders..." Lee concluded that the burn of the chilies and not their taste was responsible for the gustatory sweating. However, taste can play a role in a pathological version of the phenomenon. For example, when the nerves that go to the salivary glands are damaged, they sometimes regrow into the sweat glands. When this happens, substances that normally would cause salivation cause sweating (Frey's syndrome). Reference:
Lee, T.S. (1954) Physiological gustatory sweating in a warm climate. Journal of Physiology, 124:528-542.




q Why do dairy products stop the burning feeling after eating a hot pepper? Mitchell

A No one is sure. However, there are scientific studies that support the observation. For example, Nasrawi and Pangborn (1990) showed that both sugar and whole milk were effective at reducing the oral burn of capsaicin. Another very effective way to reduce the burn is to eat or drink something cold. This may be why ice cream is a favorite after eating hot foods! Reference:
Nasrawi, C.W. and Pangborn, R.M. (1990) Temporal effectiveness of mouth-rinsing on capsaicin mouth-burn. Physiology and Behavior, 47:617-623.




q Why are some people supertasters and some not? I'm wondering what might be some evolutionary advantages to being a supertaster. (Asked by many viewers)

A Some people have speculated that there might be advantages or disadvantages to being a supertaster based on the environment. It is important to understand that taste scientists believe that the bitter taste evolved as a poison detection system. During evolution, supertasters would have had an advantage in environments with lots of poisonous plants with bitter tastes. The supertasters would have perceived the greatest bitterness and thus would have been the most likely to avoid the plants.

On the other hand, in an environment with bitter plants that are not poisonous, the nontasters have the advantage because they have a bigger food world. Dr. Adam Drewnowski has speculated that this could be happening right now. Some bitter tasting foods contain phytochemicals which are actually healthy to eat (e.g., protect against cancer). Supertasters might like these foods less, eat fewer of them, and suffer from diseases that those foods might have prevented. Supertasters perceive the most intense sensations from salt, acids, and sweeteners as well as from fats in foods. Thus one's ability to taste PROP may turn out to be important to a variety of health problem where diet plays a role.




q My students asked about the cause of the cool sensation that occurs in a person's mouth when they eat a mint. Although this is opposite of what occurs when you eat a pepper, I hope you'll be able to help us understand this phenomenon. Timothy, High School Science Teacher, Calvary Baptist Academy

A I am not an expert on cool mouth sensations but I gave this question to my colleague, Dr. Barry Green (for more information you can contact him at Green@JBPierce.org). Peppermint contains menthol and menthol stimulates neurons that respond to cold temperatures. Thus menthol mimics the sensory input that would be produced by touching your tongue with something that is cold. This is similar to the oral burn produced by capsaicin. Capsaicin stimulates neurons that respond to irritants. Thus it produces burning sensations.



q How can I get one of those little wafers you gave to Alan. I want to find out if I'm a "taster" or a "non-taster"? (asked by many viewers)

A We make the PROP papers. In order to give them to people to taste, I must have the permission of the Institutional Review Board at Yale and I must explain how they are made to any person about to taste one so that she/he can give "informed consent." For this reason, we cannot make them generally available. However, you can find out whether or not you are a supertaster by looking at your tongue. Supertasters have the most fungiform papillae (mushroom-shaped structures that hold taste buds). Check the Are You A Supertaster activity from the Frontiers teaching guide to find out how to count your fungiform papillae.



q Some friends and I tested ourselves to see if we were supertasters, tasters or non-tasters. Although our sample group of seven was statistically insignificant, we did notice that the tasters (four people) were "less slim" than the one very thin supertaster or the three average-sized non-tasters. Have you explored any correlation between weight and taste-grouping? Margoleath

A There is a small relation between PROP tasting and body weight if you test a very large number of people. Since weight varies with height, we calculate body mass index (BMI) which is a measure of weight corrected for height. The formula for BMI is: weight (in kilograms) divided by height (in meters) squared. You can get your BMI and one point of view about weight and health from this web site (www.shapeup.org/bmi/index.html). However, experts do not agree about what weight is most healthy. For more information, visit the Council on Size and Weight Discrimination (www.cswd.org).

We asked over 2500 people (various races, both males and females) to rate the bitterness of PROP paper (the paper you saw Alan Alda taste) and provide their weight and height. We divided people into two groups: those with a BMI less than or equal to 25 (some experts consider this "normal" weight) and those with a BMI greater than 25 ("overweight"). For people who had a BMI of 25 or less, BMI decreased slightly as PROP bitterness increased (for those interested in statistics, r=.13, p<.0001); that is, nontasters had an average BMI of 22.0 while supertasters had an average BMI of 21.2. For people who had a BMI over 25, BMI increased slightly as PROP bitterness increased (r=.09, p<.01); that is, nontasters had an average BMI of 28.8 while supertasters had an average BMI of 30.8.

This raises an interesting issue. Supertasters perceive more intense sensations from tastes and fats in food. Among thin people, supertasters tend to be the thinnest. Among heavy people, supertasters tend to be the heaviest. Do you have any ideas about why this might be true? We don't know the answer yet.




q My class was wondering if there was any significance in the fact that all the tasters in the McCormick lab were women? Is there a higher rate of supertasters among women? Lisa

A There is an association between sex and supertasting. Women are more likely to be supertasters than men. There is also an effect of race but we know less about that. We know that Asians are more likely to be supertasters than Caucasians but we do not have enough data to draw conclusions about African Americans and Hispanics (this would make a wonderful research project!). Among American Caucasians, about 35% of women are supertasters and about 15% of men are supertasters.



q I would like more information about the capsaicin (hot pepper) cream treatment shown to help neuropathy. Where can I get more information (on the web or by conventional means? How can I find out where this treatment is offered? Can you provide titles of any journal articles that describe this treatment? (asked by many, many viewers)

A These questions deal with Dr. Wendye Robbins' use of very high concentrations of capsaicin to treat the patient's feet at Mt. Zion Hospital in San Francisco. The treatment is described in a paper published in the journal Anesthesia and Analgesia. Here is the reference and the abstract.

Treatment of intractable pain with topical large-dose capsaicin: preliminary report. Robbins WR, Staats PS, Levine J, Fields HL, Allen RW, Campbell JN, Pappagallo M Anesthesia and Analgesia 1998 Mar;86(3):579-83

Complex regional pain syndromes (CRPS) and neuropathic pain are often poorly controlled by conventional pharmacologic interventions. We administered 8-methyl-N-vanillyl noneamide (capsaicin) at doses of 5%-10% to individuals with such disorders in this trial. Previous limitations to trials with larger-dose, topical concentrations of capsaicin included intense burning sensations experienced after application. To enable patients to tolerate the concentrations, we first performed regional anesthesia. All patients reported at least some relief. Of 10 patients, 9 obtained substantial analgesia that lasted 1-18 wk. At Week 1 after therapy, the mean verbal analog scale (VAS) scores decreased from 8.0 to 3.0. At Week 4 after therapy, mean VAS score was 4.5. Analgesia lasted from less than 1 wk (1 patient) to more than 50 wk (1 patient). Patients received one to eight treatments. With one exception, patients receiving more than one treatment obtained additional relief with subsequent treatment. Pain responsive to opioids was the only side effect of treatment. Large-dose capsaicin administered with regional anesthesia may effectively minimize refractory CRPS and neuropathic pain. A double-blind, placebo-controlled study in patients with bilateral peripheral neuropathy using epidural anesthesia with and without large-dose topical capsaicin is in progress.
IMPLICATIONS: Sensory neuropathies are associated with many diseases. Pain from these disorders can produce greater disability than the primary disease processes themselves. Currently available therapies are limited. However, the intermittent application of large-dose topical capsaicin may provide significant pain relief, decrease chronic analgesic dependence, and decrease aggregate health care expenditures.
If you are interested in finding out more about the research presented by Dr. Wendye Robbins,of UCSF Mt. Zion Medical Center who was featured on 904 doing capsaicin desensitization, please contact her directly. Wendye is an anesthesiologist specializing in chronic pain. You can reach her at:
Her address is:
Dr. Wendye Robbins
UCSF Mount Zion Medical Center
2255 Post Street, San Francisco, CA 94143-1654
E-mail: wendye_robbins@quickmail.ucsf.edu
Phone: 415-885-PAIN




q Are there any studies being done to determine if this capsaicin-based treatment can help other conditions, for example, Raynaud's Disease, arthritis, spinal stenosis, chronic low back pain, severe joint pain? (asked by many, many viewers)

A There are many published studies of the use of commercially available capsaicin creams (e.g., Zostrix) to treat a variety of types of pain. The problem with these treatments is that the skin is a very good barrier to capsaicin. Thus most of the capsaicin that you put on the skin does not get to pain receptors. This is why Robbins et al had to use very high concentrations on their patients. The commercial creams are available in most drug stores.

Using capsaicin in the mouth does not have the same problems because the tissue in the mouth is not a good barrier to capsaicin. Thus low concentrations of capsaicin are effective at desensitizing pain receptors in the mouth.




q Is there an over-the-counter or prescription substance that is available for tongue sores or other mouth pain similar to the hot pepper candy that Alan was helping make on the show? (asked by many viewers)

A There is no currently available capsaicin candy but we expect there to be such a candy available commercially within the next year. In the meantime, patients can make their own. The recipe is published in the following two references.

Berger, A.M., Bartoshuk, L.M., Duffy, V.B., and Nadoolman, W. Capsaicin for the treatment of oral mucositis pain. In V.T. DeVita, S. Hellman, S.A. Rosenberg (Eds.) Principles & Practice of Oncology updates, Vol. 9, Philadelphia: J.B. Lippincott Co., 1995 Pp. 1-11.

Berger, A., Henderson, M., Nadoolman, W., Duffy, V., Cooper, D., Saberski, L., Bartoshuk, L. Oral capsaicin provides temporary relief for oral mucositis pain secondary to chemotherapy/radiation therapy. Journal of Pain and Symptom Management, 1995, 10, 1-6.


Here is the recipe:

Capsaicin candy
1 cup sugar
3/4 cup light corn syrup
2/3 cup water
1 Tbs. cornstarch
2 Tbs. butter or margarine
1 tsp. salt
2 tsp. butter flavor (for butterscotch candy)
1/2 tsp. cayenne pepper
We have data on McCormick cayenne pepper so if you use that brand your candy will contain about 7 ppm capsaicin.

Butter square pan, 8x8x2 inches. In 2-quart saucepan, combine sugar, corn syrup, water, cornstarch, butter and salt. Cook over medium heat, stirring constantly, to 256° on candy thermometer (or until small amount of mixture dropped into very cold water forms a hard ball). Remove from heat; stir in butter flavor and cayenne pepper and pour onto a cool surface (e.g., cookie sheet).

When just cool enough to handle, pull taffy until satiny, light in color and stiff. If taffy becomes sticky, butter hands lightly. Pull into long strips, 1/2 inch wide. With scissors, cut strips into 1-inch pieces. Wrap pieces individually in plastic wrap or waxed paper. (Candy must be wrapped to hold its shape). Makes about 1 pound.

How to use:
Hold the candy in your mouth and let it dissolve. The candy should contact the areas in your mouth that are painful. The burn of the candy will build slowly. After the candy has dissolved (this will take about 10 minutes), the burn of the candy will slowly fade (this may take up to 15 minutes). If your pain is substantially less than it was originally, then the capsaicin has successfully desensitized pain receptors responsible for the pain.

The candy may fail to reduce your pain. This may occur because your pain does not originate from receptors close to the surface of the skin (these are the receptors that capsaicin can reach). If the burn of the candy was considerably lower than your pain intensity, the candy strength may be too weak. You can successively desensitize with higher and higher concentrations of cayenne pepper in candy to see if this will help. If the burn of the candy is too high, you can begin with a lower strength candy.

Alternative candy:
Melt 1 pound caramels. Add 1/2 tsp. cayenne pepper. Mix well and drop by teaspoonfuls onto wax paper.




q I enjoyed the show but was disturbed during the segment on chile peppers when a pepper solution was applied to "living tissue" and the interviewee described the reaction as a "silent scream." It occurred to me that the solution may have been applied using animal testing, and I was upset by my suspicion. Was my conclusion correct? I am of the opinion that perhaps some medical testing may be required, but that the inflicting of pain solely to make a point is unconscionable. Sue Bonham

A (From the Webmaster) I forwarded your e-mail regarding testing chile pepper solution (capsaicin) on animals to Wendye Robbins, the scientist featured on the Scientific American Frontiers show "Life's Little Questions" who is doing research with capsaicin. She reports that no animal testing has been done by her or her group, and she isn't aware of any animal testing that occurred in the past. The "silent scream" Michael Caterina mentioned on the show was in reference to his in vitro ion channel response to capsaicin application. The work currently being done by Wendye and her colleagues is focusing on the way the chile works, and not on clinical trials





Linda Bartoshuk is also featured in Cool Careers in Science. Check it out!




 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.