Taste receptors don’t only exist in your mouth. You can find them all over your body, including your stomach, your lungs, and your colon. Why? It turns out the taste receptors are much more versatile tools than we suppose.
Some of you might have developed a taste for bitter foods. Those few are probably skinnier than the rest of us. Bitter-flavored compounds have an effect on us as they are digested. The effect takes about a half hour, and it kicks in only after a decent meal, but eventually the bitter flavor causes the stomach to stop emptying, making us feel fuller longer. Researchers think that the stomach is holding on to the food because bitterness can be a sign that food is dangerous to eat, and this is a way to keep the body from getting a full dose of toxic compounds at once.
The reaction of the stomach doesn’t immediately make sense. Bitterness can be the result of all kinds of different chemical combinations, only some of which are dangerous. The stomach holds on to food only in response to bitter flavors, and not actual dangerous poisons. How does the stomach know what’s bitter and what’s not?
The stomach has taste receptors of its own. After all, taste buds on the tongue are just chemical identifiers that are hooked up to our conscious mind in order to get us to keep wolfing down certain chemicals. The taste receptors in the stomach aren’t hooked up to our conscious brain, but they are hooked up to some kind of sensory response system, and when that sensory system notes a lot of bitter-tasting food, it puts the brakes on digestion.
And a good thing, too. Taste receptors really are everywhere, including the colon. And if it gets exposed to too much bitterness, it triggers a release of ions, which in turn causes water to pour into the gut via osmosis, and the body experiences diarrhea. So if you want to be lean and healthy, eat enough bitter food to keep you full, but not enough to empty you out.
[Source: Neuroscience: Hardwired for Taste]