Yo big eaters, chew slower

Were you trained to eat everything on your plate, down to the last tough silverbeet stalk? Are you a slow or a fast eater? Were you panicked by competing siblings into wolfing down your food? How many times do you chew each mouthful? Does it matter?

Marco Morgenstern​ and Esther Kim​ at Plant & Food Research​ are researching our little-studied chewing habits for the Riddet Institute​ – how they affect taste, digestion generally, and even the populations of bacteria in our bowels.

Comparing NZ-Europeans with Chinese (Hangzhou,​ near Shanghai)​ and NZ-Koreans – 100 people in each group – they found that the New Zealanders of European descent take bigger bites, eat faster (smaller number of chews) and have less saliva mixed with each mouthful.

Chewing longer adds more saliva, breaks down the food into smaller bits, and allows more time to enjoy the flavours. It also results in faster absorption of sugars into the bloodstream.

A standout difference between the Chinese and the NZ-Europeans was the peak level of sugar in the blood a short time after eating the same amount of brown rice. In the Chinese cohort, it was a whopping 40 per cent higher, and stayed higher for some time. Even though other factors like genetics come into play, chewing habits have an influence on blood glucose levels.

Texture is an important aspect of eating enjoyment and is key to whether people like a food. Kim and Morgenstern found variations between people of different ages among their research cohorts.

For example, older people in each group prefer the harder kettle fries over thin chippies, whereas younger Chinese and NZ-Koreans, who have become used to a lot of soft, highly processed foods – yoghurts, cakes, fluffy white bread – prefer the thinner, softer chippies.

So what, you say? They have the choice. In fact, quite a lot is at stake for our food designers and exporters when it comes to differentiating and targeting overseas market niches.

As we know, there are individual differences in taste and eating habits. Each person has a unique mix of genetics, culture, diet habituation and age. Taste and textural enjoyment from food are in the mind, just like colour and sound.

There is no objective measure, and getting people to describe what they taste is hard, so psychologists are deployed to help with this aspect of the research.

We hear a lot about the importance of the microorganisms which live in our bowels and feed on undigested leftovers. They have their own preferences. Lab experiments showed that 16 hours after eating, short vs long chewing resulted in differences in the relative abundance of certain types of bacteria. Experiments in actual humans will test these results.

Kim and Morgenstern hope their research will ultimately help our nutritionists and food innovators cater to different tastes and physiological needs. Older people tend to produce less saliva, and are less able to chew, but still want taste and texture. How can we make eating more pleasurable for them?

Athletes may want an immediate energy boost, while others, like the growing number of diabetics, need a slow and steady rate of energy input. How can we contribute to mitigating the obesity issue by slowing down our big eaters so that they feel satisfied sooner with less? There’s more to chewing than you think.

Originally published in Stuff/Dominion Post on Monday 22nd November 2021. Co-authored by Marco Morgenstern and Esther Kim at Plant & Food Research, and science writer Glenda Lewis, and funded by the Riddet Institute.

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