Do You Chew, Or Do You Smoothie? by Joan Kent, PhD

Do You Chew, Or Do You Smoothie?
By Joan Kent, PhD

Are your mouth and jaw getting the food workout they need? Here’s why we should eat – rather than drink – our food and chew it thoroughly.

Chewing Starts the Digestive Process

Digestion begins in the mouth. Saliva contains amylase and lipase, enzymes needed for starch and fat digestion.

Adequate chewing increases saliva to lubricate food, which eases its passage through the esophagus when we swallow.

Chewing signals the GI tract to prepare for food. The stomach makes gastric juice, comprised of enzymes, hydrochloric acid, and other substances. The pancreas prepares to secrete enzymes and bicarbonate into the small intestine. Extra saliva relaxes the pylorus so food can exit the stomach and move into the small intestine.

Enzymes and stomach acid work on the surface of food only. Chewing increases the surface area available for them to work. That’s especially important for the digestion of protein, which has many functions in the body.

But all foods need to be chewed small enough for stomach acid to further reduce them in size. That enhances bioavailability, the faster release and fuller absorption of nutrients and fluids into the GI tract.

In fact, most of the foods we don’t chew enough tend to be carbohydrates, such as bread and rice. They absolutely need amylase for digestion, but can be easy to swallow without adequate chewing.

Dogs eat carbs the right way. A dog will simply swallow meat; its digestive system can process meat in that whole state. Give a dog a piece of bread, though, and the chewing begins.

But back to humans…

Chewing Increases Satiety, the Had-Enough Feeling

Sensors throughout the GI tract monitor nutrient levels and the amount of chewing, tasting and swallowing involved in a meal. Giving your mouth and jaw a good food workout can bring on fullness signals sooner.

Foods with harder, crunchier textures – apples, raw broccoli, carrots, celery – require more chewing. They also provide more nutrients than semi-soft fats, or junk foods. So choosing foods that require lots of jaw action could lead to greater satiation, which ends the meal, and satiety, which determines how soon we want our next meal.

Chewing longer helps to raise glucose levels. Those in turn raise insulin levels. Insulin is involved in satiety and feedback loops that end a meal, again marking chewing as a key satiety factor.

What About Hormones?

Chewing thoroughly helps to release higher levels of CCK (cholecystokinin). CCK is a powerful satiety hormone, so releasing more of it can decrease appetite for a longer time.

CCK is released primarily when we eat protein and fats, but its satiety function tends to be specific to carbs.

The chewing-and-CCK connection could help vegans, for example. They often have strong cravings for carbs generally and sugar in particular, due to their low protein intake and low levels of CCK. Chewing foods for a longer time could help vegans eliminate sugar cravings by increasing their CCK levels. (So could more protein, but that’s another article.)

Then there’s ghrelin, truly a monster hormone. It increases appetite and decreases energy expenditure. Yikes. More chewing increases satiety by decreasing levels of ghrelin.

In a country that produces 3950 calories per day for every man, woman and child, no one needs more ghrelin. So if simply chewing longer can reduce ghrelin levels, by all means chew longer.

Longer chewing time appears to be more important than gastric volume when it comes to satiety.

Chewing May Help With Weight Loss

In a research study, participants consumed 150 calories prior to serving themselves from a buffet meal. The ones who had been given a pre-meal snack of solid food ate about 150 calories fewer from the buffet, compared with controls.

Those given the 150-calorie snack in liquid form, though, did not decrease their meal size.

Eating fast, taking large bites, and swallowing quickly after less chewing are behaviors that tend to be associated with overeating and higher body weight.

Hard foods (raw broccoli and the like) may decrease bite size, while soft foods (ice cream, cake, pudding) tend to increase bite size. Hard foods also require more chewing, slowing down the meal.

Another study compared pizza chewed 40 times with 15 times per bite. Chewing longer left participants feeling less hungry, less preoccupied with food, and with a decreased desire for food.

Chewing 40 times per bite also increased plasma glucose and insulin, which increases satiety, as described above. So longer chewing time may decrease food intake at a given meal.

But the longer chewing time did not decrease intake at the next meal, given 3 hours later.

Not surprisingly, longer chewing needs to be repeated at each meal to reduce calorie intake successfully.

Chewing May Increase Dining Pleasure

Chewing is a large part of mindful eating, which includes savoring the aroma, anticipating each bite, and experiencing each bite fully. Longer chewing releases more flavors from foods, and longer contact with the taste buds may lead to greater satisfaction with the meal – as well as a greater sense of fullness and satiety.

All of this can decrease the total amount of food eaten at a meal. The pleasure from a given food decreases during the meal. It’s commonly referred to as the “satiety cascade,” but I learned it in science journals as “aliesthesia,” a decrease in a food’s palatability as hunger subsides.

Staying more aware of the change in taste sensation by chewing longer could focus the meal on quality instead of on quantity. That may be particularly true if and when the meal slows down.

Again, choosing harder foods with crunch and texture will take longer to eat and may contribute to increased satisfaction with the meal.

Increase Oral Processing Time (Say What?)

In general, keep food in your mouth longer. Here are guidelines.

• Eat when you’re physically hungry so your body is really ready for food.

• Include plenty of harder, crunchier foods, like vegetables.

• Take small bites.

• Don’t chew right away. Hold the food in your mouth for a moment or two before starting to chew.

• Slow down. The method that seems to work best is to start the meal at a normal rate until the initial hunger has passed. Then slow to about half speed.

• Chew longer! This may be an individual thing that takes some explanation:

Apparently, we don’t like chewing food more than we have to, and that can vary with a given food. In the pizza study above, researchers postulated that 40 times per bite changed the characteristics of the food enough to make the food less appealing and decrease appetite.

Maybe it’s necessary to get used to this new eating practice by counting at first. Once the habit is there, instead of counting chews per bite, just chew till the texture of the food – not the taste – no longer reveals what the food is. For example, if you can distinguish between a broccoli stalk and a floret in your mouth, you need to keep chewing.

Whatever your reason for chewing more – better digestion, better health, greater dining pleasure, increased satiety, weight loss – all can start with this one change.

“Nature will castigate those who don’t masticate.” – Horace Fletcher (1849-1919)

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