While it's widely known that chewing more improves digestion, research suggests it can also boost our brains and even help fend off Alzheimer's.
For once chewing a shallot 722 times before swallowing it, Horace Fletcher was dubbed "The Great Masticator". The American self-taught nutritionist believed food should be chewed "until it is completely liquefied" and "practically swallows itself." Fletcher's doctrine may have been a little extreme, "but in some aspects, he was actually right," says Mats Trulsson, professor in the department of dental health at the Karolinska Institutet in Sweden.
Chewing more can provide a wide range of health benefits, from improving digestion and helping people consume fewer calories to alleviating stress and anxiety and improving cognition by solidifying memory skills and boosting attention span.
The prehistory of chewing
Like most animals, humans have had teeth and jaws for millions of years. The earliest hominins, who lived roughly six to seven million years ago, had teeth especially helpful for eating large, fleshy fruit. But as forests gave way to woodlands and savannah-like environments, hominins had to contend with more mechanically challenging foods — seeds, nuts, and tubers. So they evolved bigger molars, larger jaws, and stronger muscles.
With the development of tools, food processing, and cooking with fire, we stopped needing such lengthy bouts of chewing. Today, humans spend roughly 35 minutes chewing every day, compared to 4.5 hours for chimpanzees. Despite these evolutionary changes, the purpose of chewing remains the same: to get as much energy as possible out of our food.
An important first step
At the most basic level, chewing breaks food down into small particles and moistens them with saliva so they can be easily swallowed. "It's the first phase of digestion," says Andries van der Bilt, a pioneer in oral physiology who spent over three decades at the University Medical Center Utrecht.
Chewing increases saliva production and digestive enzymes like amylase that help break down food, and also triggers the gut and pancreas to prepare for what's coming. "If you don't chew, the gut is not prepared to handle food," says Trulsson. Bigger food particles linger in the gut longer, giving microorganisms more time to ferment them — causing bloatedness, fullness, and constipation.
Improving absorption and feelings of fullness
Chewing also helps release nutrients so our bodies can absorb them more effectively. In one study, 13 healthy adults chewed a small handful of almonds either 10, 25, or 40 times. Researchers found that the more people chewed, the less fat they excreted — suggesting energy absorption from the nuts was up to a third higher with more chewing. Chewing 40 times also left participants feeling fuller for longer.
Chewing more means you're also likely to consume less food overall, according to two separate meta-analyses reviewing nearly 50 studies. It takes around 20 minutes for the body to send signals to the brain that you're full — and chewing buys you more time. One good way of slowing down your eating rate is to choose more textured foods: solids over liquids, and high-viscosity foods like oatmeal over white rice or pasta.
A boost for brain health
Researchers are increasingly finding that chewing plays an important role in brain health as we get older. Tooth loss has been linked with a higher risk of Alzheimer's disease and dementia. In a survey of more than 28,500 people older than 50 across 14 European countries, those with good chewing ability performed significantly better on cognitive tests — including word recall, verbal fluency, and numeracy — than those with chewing problems.
Why does chomping ability affect memory? Some researchers point to the multiple neural circuits connecting our chewing apparatus to the hippocampus — the region of the brain responsible for making new memories, and one of the first areas damaged by Alzheimer's. Others suggest that chewing may increase blood flow to the brain. "The theory is that chewing works like a pump, pumping blood to the brain," explains Trulsson.
To find out whether poor chewing ability can cause cognitive decline — and whether rehabilitation is possible — Trulsson's team is currently running an experiment replacing patients' missing teeth with implants and studying their brain function before and after the procedure. "Wouldn't it be really cool if you can rehabilitate the brain by rehabilitating the dentition?" says Trulsson.
Heightening alertness and lowering stress
Chewing has also been found to improve concentration. One meta-analysis of 21 studies found a statistically significant improvement in attention levels among gum-chewing participants during cognitively demanding tasks, though the effect lasts only around 15 to 20 minutes.
Outside the lab, chewing is a good stress-reliever too. When researchers studied 100 nursing students preparing for mid-term exams, those who chewed gum for at least 30 minutes daily experienced lower levels of stress, anxiety, and depression. Chewing seems to be a natural reflex in stressful times. "When some people are stressed, they start to chew unconsciously," says Jianshe Chen, an oral processing researcher at Singapore's Agency for Science, Technology and Research.