Beefing up bites: Soft chow weakens modern jaws

The Yomiuri Shimbun

Hectic modern lives have led to a boom in soft, easily prepared food that can be wolfed down in an instant. These meals may be convenient, but they also may weaken our power to chew.

Taeko Kanemoto, a children's dentist in Funabashi, Chiba Prefecture, pays attention to the mothers who bring their children to her clinic. Mostly in their 20s and 30s, the women often let their mouths hang open while they listen to Kanemoto, and the corners of their mouths become loose when they talk about their children.

Kanemoto also said these women do not speak smoothly. When they try to say "ta, chi, tsu, te, to," it sounds like "taa, tei, tou, teh, toh." When they bring their children to the clinic, they often complain about their own problems, such as a poor bite or pain in the jaw.

Speaking with them, Kanemoto found the women eat a lot of soft food, things popular with children like hamburger steaks and gyoza, and rarely eat harder things such as dried sardines and beans.

"Since they don't chew as much with soft food, it seems like they've lost strength in their jaws," said Kanemoto, who teaches proper chewing at a primary school.

Shigeru Saito, head of the Nationwide Shokuiku Practice Society and the former head of Japanese Society for Mastication Science and Health Promotion, studied chewing frequencies and meal times throughout history by recreating meals from different periods.

He found that modern people chew an average of 620 times in 11 minutes for a meal of hamburger steak and spaghetti. However, a meal from the Yayoi period (about 300 B.C. to A.D. 300) that included steamed brown glutinous rice and walnuts required more than six times the number of chews and about five times as long to finish as modern meals. Even a meal from just before World War II required double the number of chews and twice the time.

"If the bite isn't intentionally developed from childhood, a person's jaw won't develop properly and they might end up with an abnormal bite or arthritis of the jaw," Saito said.

To deal with the problem, an increasing number of schools have started programs to develop children's bites as part of dietary education.

At Takagi No.2 Primary School in Takagimura, Nagano Prefecture, children have been wearing sensors on their jaws to count how many times they chew during lunch since the spring of 2008. At first, many children finished eating within 10 minutes and only chewed 600-700 times, but most now take about double the time and twice the number of chews.

"Children have become used to chewing their food well and taking more time to finish lunch. It also keeps them from eating too quickly and getting fat," said Kazuko Yasutomi, a nursing teacher at the school who helped develop the sensor. The device has been commercialized and is now used at schools in Nagano and Chiba prefectures.

Other surveys have indicated that teeth become weaker when the bite loses strength, and that people who do not eat hard food tend to have larger waistlines.

Changes in our bodies warn us about about distortions in our eating habits.