Have you ever taken a bite from a dish only to discover that your mouth is on fire? When we eat dishes that contain ingredients like chili peppers or jalapenos, the first thing that come to a lot of people's mind is, "Dang, that food is SPICY!" And what exactly "makes" the food taste spicy? Do we taste spiciness the same way that we taste sweet or salty foods? The answer is No. No, we don't.
Lining our tongues are thousands of pink colored bumps called papillae. Within each papillae are thousands of taste buds that contain numerous sensory cells, which in essence, can function as fluid-filled funnels/channels. These cells, along with our olfactory sense and trigeminal nerve fibers, help us differentiate between the 5 basic tastes: Sweetness, sourness, bitterness, saltiness, and savoriness/umami, Contrary to what a lot of people believe, spiciness is actually not triggered by the sensory nerves in the taste buds. The burning sensation is actually induced when plant-derived compounds like capsaicin from chili peppers activate trigeminal nerves that express the TRPV1 receptors. The direct activation of these nerve fibers cause the somatosensory fibers that are located on the tongue to interpret this as "hot" or "spicy".
WHAT EXACTLY IS CAPSAICIN?
Capsaicin (CAP) is a term that was first coined by a chemist named Christian Friedrich Bulchoz. It's an active and pungent chemical compound from chili peppers and has been studied extensively since its discovery back in 1919. This molecular compound, also known as 8-methyl-N-vanillyl-6-nonenamide (C18H27NO3), belongs to a class of compounds called capsaicinoids and can trigger the pain receptors that are located on the tissues in your body.
OUR BRAIN ON CAPSAICIN
Spicy foods can excite pain receptors on the skin that normally respond to heat. These receptors, also known as polymodal nociceptors, respond to extremes in temperature, mechanical stimulation, and chemicals that are flowing through our central nervous system (CNS). When we eat spicy foods, capsaicin binds to vanilloid receptors called VR-1 and TRPV1 that are located on the nerve endings of C-fibers.
In the absence of capsaicin, these ligand-gated ion channels (VR-1 and TRPV1) are normally closed. However, when the capsaicin binds to these receptors, they start opening up and an influx of sodium and calcium ions enters these channels. An action potential is initiated and the neural signals that originate from the terminals of the receptors are propagated to second-order neurons in the CNS. It triggers other nerve cells and not only cause the brain to think that the body is being exposed to a dangerously high temperature, it also stimulates the nerves that respond to mild increases in temperatures as well. These are the reasons why capsaicin makes our tongue feel like it is on fire!
*Quick Note: Since TRPV1 is present on nerve cells all throughout the body, it is essential that you wash your hands after touching chili peppers. Don't touch your eyes or other parts of your body that you WOULD NOT want to burn!
Now, we know that the capsaicin in spicy peppers can cause a burning sensation on our tongue, mouth, and anywhere that it touches. If it's so painful, why do we keep eating it?? The main reason why is because capsaicin tricks the body into thinking that it's being burnt. However, because our body is trying to protect itself, the brain responds by releasing endorphins - which are peptide hormones that are produced by the CNS and the pituitary gland, as well as dopamine - a neurotransmitter that plays a major role in the reward/pleasure behavior. Basically what happens is that it depletes the neurotransmitter of painful impulses known as substance P from the sensory nerve terminals. Therefore, whenever you eat lots of spicy food, we start to experience a sense of euphoria and elation that is similar to a "runner's high".
HOW TO DEFEAT THE HEAT!
If you love spicy foods but cannot handle the heat, then dairy products can definitely help lessen the burn! Normally, when people eat something that's too spicy, the first thing they should do is to take a big gulp of water right? WRONG. NOPE. Don't do it. I repeat, DON'T DO IT. Water will only make it worse. If you take a look at the chemical structure of this pungent compound, you will notice that capsaicin has a long hydrophobic/hydrocarbon tail. Hydrocarbons tend to be nonpolar and have negatively charged electrons and positively charged protons evenly distributed throughout. Therefore, when you drink milk, eat ice cream, or any other dairy products that contain nonpolar molecules, they will attract and surround the capsaicin molecules, effectively soothing the burn that plagues our tongue!
On the other hand, water is a polar molecule. This basically means that it leaves the oxygen side of water with a partial negative charge and the hydrogen side with a partial positive charge. One side of the polar molecule will develop a partially negative charge while the other will develop a partially positive charge when it binds to atoms with higher electronegativity. Thus, when you drink water, it will only spread the capsaicin oil around our mouth, making the pain worse.
REAL WORLD APPLICATIONS
Due to the effects that it has on the human body, scientists have been studying capsaicin's biological responses and its mechanisms in dealing with conditions such as rheumatoid arthritis, neuralgia, diabetic neuropathy, as well as other syndromes that deal with the central and peripheral nervous systems. In many randomized and double-blind studies, researchers have found that while the topical application of lower concentrations of capsaicin (approx 1.5% to 7.5%) can be an effective treatment for osteoarthritis pain, the transient application of higher concentrations of capsaicin (around 8%) helps reduce neuropathic pain. When capsaicin is being applied topically or injected into the skin, it will also lead to the desensitization of the A-fiber and C-fiber nociceptors (afferents that are responsible for the pain from capsaicin) to heat stimuli as well.
I'm Linh - a science geek who loves experimenting and tinkering with recipes! I hope that this blog brings more ideas into your kitchens! Happy eating folks! XOXO