The concentration of these chemicals determines degree of the sensation and depends not only on the kind of chili, but on other factors including what part of the fruit you eat—the hottest part is the placenta (white part in the middle), followed by the flesh (exocarp, mesocarp, endocarp) and the seeds; fruit maturity and water content of the chili also affect pungency (unripe—ripe—dried).
In nature, the capsaicin is primarily used by the plant for defense to inhibit herbivorous mammals from eating it—the spice does not affect birds who eat the fruit and spread the seeds.
Mechanism of Action
Capsaicinoids are irritants and inflammatory molecules that interact with transient receptor potential vanilloid 1 (TRPV1) that reside on the ends of nociceptive A-delta and C- sensory fibers. These receptors are activated by capsaicinoids, noxious heat (greater than 109.4 degress Fahrenheit), caustics (low pH), and voltage—causing a Ca++ and Na+ action potential influx that confers the sensation of pain and burning to the brain. They are found in large numbers in the mouth, throat, and stomach, as well as throughout the body.3
Sensation, Not Taste
Capsaicin and the capsaicinoids are not detected by our taste buds and have no flavor—not salt, bitter, sweet, sour, or umami. They create a chemesthesis stimulus we interpret as “spiciness,” which is a multimodal somatic sensation (not just taste, olfaction, pain, temperature, or itch). The resultant “heat” we feel after exposure is not thermally hot (a thermometer in my scorched mouth would read normal), but a result of the cross-stimulation of these vanilloid molecules binding to a thermal receptor—the sensory experience transmitted centrally is interpreted as ‘burning.4
Despite not being a taste, a five part standardized lexicon for chili pepper hotness exists:1
- Development (how fast it comes on)
- Duration (how long the burn lasts)
- Location (where in mouth/throat)
- Feeling (“sharp” vs. “flat” heat)
- Intensity (analytically measured heat level)
Capsaicin has a unique attribute among natural irritants—the excitation it evokes is followed by a period of decline or cessation in sensory transmission (called defunctionalisation) for a variety of other stimuli. This attribute is exploited by frequent eaters of spicy foods (they don’t feel it as much as novices), and pharmaceutical products.5
Human Effects
The human response to capsaicin exposure ranges from enhancing food enjoyment to uncomfortable to unbearable depending on the dose of exposure and resultant receptor agonism. Oral exposure creates a spicy burning sensation (or pungency) in the mouth that can extend to the throat and stomach (and eventually the rectum—“fire tuchus”). This is frequently accompanied by diaphoresis, facial flushing, lacrimation, and rhinorrhea. Higher dose exposures to the irritant can result in nausea, vomiting, chest, and abdominal pain.
Pages: 1 2 3 4 | Single Page
No Responses to “Toxicology Answer: The Capsaicin Found in Hot Peppers and Chilis”