A few years ago, I had a friend whose jaw was wired shut for a time. Although she was in great pain for several weeks, the only thing she really complained about was the unsatisfying experience of subsisting on a liquid diet, which she said just wasn’t the same as eating real food. Another old friend of mine completed two weeks of a cleansing lemon-juice fast, but her willpower was eventually sunk—not by the desire to eat, per se, but by the desire to chew. More than pizza, chocolate, or cheese, these women missed the sheer act of chewing most of all.
Considering that so many of us eat our meals on the run, in front of the television, or at our desks, we think of chewing as a means to an end—just a way station on food’s journey to the stomach. Actually, the act of chewing is much more important than we give it credit for, both physically and psychologically.
Slow Down, You Chew Too Fast
The primary purpose of chewing is to break food down into smaller pieces for easier passage through the digestive tract, but there are other reasons why smaller is better. Our saliva contains enzymes that begin the digestive process; when food particles are smaller, they have more surface area, and by coating them, saliva can begin to break them down immediately, making things easier for our stomachs and allowing our bodies to absorb more of the nutrients and minerals the food contains. Research shows that the body’s absorption of nutrients begins right in the mouth, and that food swallowed whole or in large chunks isn’t digested as fully as food that’s chewed thoroughly, which means many beneficial nutrients go to waste. Large bites or chunks of food also tend to be accompanied by a great deal of air, which can lead to gas, burping, bloating, and an unpleasant full sensation. It can also contribute to bacterial overgrowth in the gut, as well as exacerbate heartburn, indigestion, and IBS.
Chewing doesn’t affect just the food—it begins impacting other digestive organs even before you swallow that first bite. The process of chewing triggers the brain to send preparatory signals to the rest of the digestive system, instructing the stomach to produce hydrochloric acid for digestion and instructing the pyloric sphincter (which separates the stomach from the small intestine) to open. Chewing also causes the brain to stimulate other organs, like the gallbladder, pancreas, and spleen, to start pumping out their own digestive juices.
Our brain transmits these signals only when we take the time to chew our food properly. When we gulp down large chunks or ignore chewing altogether, many digestive functions never get triggered. Although they may begin to do their job eventually, they’re just playing catch-up for food that’s already passing through, instead of being prepared for the food in advance.
Since chewing is the process that sets the whole digestive system in motion, it’s easy to see why people on liquid diets never feel like they’re really eating. Psychologically, we’re primed to associate eating with chewing, since it’s only through chewing that we get the full experience of food, with its many and varied tastes, textures, and consistencies. That may explain why it’s common for dieters to forget about liquid calories—we often don’t count beverages as food. Another way chewing affects us is by allowing the feedback loop between the brain and the stomach to relay the signal that we’re full and it’s time to stop eating. Without chewing, eaters might not get that message until they’ve already eaten too much. One common weight-loss tactic is to chew each piece of food a certain number of times—it forces the person to eat slowly, and research shows that when we eat slower, we eat less.
Flying in the face of everything my mother taught me, several reports have cried, “Chewing gum is good for you!” Certain researchers have found that chewing gum can improve memory and reduce stress, although these experiments were actually conducted by the Wrigley Institute of Science, a think tank funded by the makers of Wrigley gum. Despite this unsurprising bias in favor of the magical effects of gum, other research supports the notion that the act of chewing is good for you—or at least good for your brain.
Building on the previous research that suggested that chewing has positive effects on the formation of memories, doctors at Gifu University in Japan have found that it might also protect the brain against dementia by activating the cerebral area called the hippocampus, which is responsible for memory. In addition, these scientists discovered that mice without teeth were more susceptible to the mental ravages of age than mice who had all their teeth intact. Although correlation does not always equal causation, their experiments raised many questions about how the act of chewing might work to keep the hypothalamus stimulated, relieving stress and preventing the deterioration that eventually leads to memory loss and dementia.
Even if we don’t do it long enough or thoroughly enough, humans like chewing and have evolved to chomp our food carefully, as opposed to animals that primarily rip and tear theirs. Dieticians recommend taking more time to chew food properly for dietary and weight-loss reasons, but it’s also important to do so to get the full flavor impact of food. Think about it—a piece of pizza that has been liquefied in a blender would contain the same nutritional properties as its solid form, but it would be significantly less appetizing. Chewing is an important part of how we eat, and as anyone who’s ever been on a liquid diet can attest, you don’t know what you’ve got till it’s gone.