Mouth burning after an extra-hot Buffalo wing or a punishing dollop of habanero salsa? Your first temptation is probably to reach for a cool drink to put out the fire.
But a new video released by the American Chemical Society explains exactly why drinking water after you eat spicy food is pretty much the worst thing you can do. Instead, you should be reaching for milk. Melted ice cream will probably do in a pinch.
It all comes down to a little substance called capsaicin (pronounced cap-say-sin), the stuff found in chili peppers that makes them spicy. Capsaicin binds to receptors in your mouth known as TRPV1 pain receptors, which tell your brain when things are spicy, hot in temperature, or very acidic. This signal can also trigger the runny nose and tears that so often accompany Szechuan food pig-outs.
The more capsaicin in a pepper, the more it binds to your receptors, and the higher the pepper will rank on the Scoville Scale, a measure of spiciness. A ghost pepper—among the hottest of all peppers—ranks at 1,000 Scoville units.
The purpose of the TRPV1 receptors is to let you know that that danger is imminent, and basically, that you should stop eating such spicy stuff. If you would like the pain to go away—so you can continue to stuff your face—then milk should be your liquid of choice.
Here's where the video gets technical and digs into why water is the worst choice for a spicy meal and dairy products the best. The capsaicin molecules that are found in peppers have long hydrocarbon tails, meaning capsaicin is a non-polar molecule. As such, it dissolves in other non-polar substances.
If you eat something spicy and drink water—a polar substance—it's as though you've mixed oil and water. Essentially, the water will spread the capsaicin throughout your mouth, making the pain even worse. Instead, if you reach for milk or another dairy product—which contain non-polar molecules—the capsaicin is pulled off your TRPV1 receptors and dissolved. And, dairy products also contain a protein called casein, which attracts capsaicin molecules, making the soothing work of milk even more effective.
This is likely why Southeast Asian cuisines often feature yogurt-based drinks that seem to work so very well with the spicier offerings in their cuisine.
If a glass of milk—or even a yogurt-based lassi—doesn't sound appealing to you as a meal accompaniment, the American Chemical Society has a bit of good news: The more capsaicin you eat, the more tolerance you build. Turns out that TRPV1 receptors can become desensitized if you eat spicy food often.
See? You can use chemistry in your daily life. And, no, we're not talking about mind-altering substances.