By Hiromasa Takeda / Yomiuri Shimbun Staff WriterTooth decay was common among children in the Kyushu region during the Edo period (1603-1867). The food — which used a good amount of sugar — was to blame, according to Tomohito Nagaoka, an associate professor at St. Marianna University School of Medicine.
Nagaoka, an anthropology expert, inspected the remains of 115 children who lived in Edo (present-day Tokyo) from the latter 17th century. They were excavated at the site of Hitotsubashi High School in Chiyoda Ward.
The associate professor compared his findings with those of another research group that examined the remains of 32 children from samurai families from the 17th to 18th centuries. They were excavated at the site where the Sogenji temple once stood in today’s Kokurakita Ward, Kitakyushu.
The research group also looked at the remains of 36 children living in towns and farming communities from the 16th to 19th centuries. They were excavated at a nearby archaeological site.
Nagaoka divided all the children into three age groups: 6 months to 2; 3 to 5; and 6 to 10.
He found that, on average, 11.7 percent of children living in Edo had tooth decay, and that the corresponding figures were much higher in the Kyushu region — 17.1 percent of children from samurai families had it, and 26.9 percent of commoner children did.
Tooth decay was more prevalent among children in Kyushu compared to their Edo counterparts across all age groups. In the group for 6- to 10-year-olds, the percentage of those with tooth decay in Kyushu was about four times higher than in Edo, regardless of social status.
Evidence of brushing teeth was found in adult remains excavated at the Sogenji site. When comparing the remains of children in Kyushu across all age groups, tooth decay was less prevalent among those from samurai families compared to commoners — except for 6- to 10-year-olds.
“I believe the habit of proper brushing was more widespread among samurai families than commoners,” Nagaoka said. “Aside from brushing teeth, there must be other factors behind why tooth decay was more prevalent in [children from] samurai families in Kyushu [compared to those] in Edo.”
One likely factor is baby food and substitutes for breast milk containing sugar. According to Nagaoka, baby teeth begin to appear about six months after birth and are replaced by permanent teeth at age 6 or 7. Therefore, tooth decay among young children is often determined by foods for babies.
Imports via Nagasaki
During the Edo period, when Japan closed its doors to most of the world, white sugar was imported via Nagasaki from various locations in Asia and then transported along Nagasaki Kaido — a road that ran through Saga to Kokura, part of today’s Kitakyushu.
“Imported sugar was brought from northern Kyushu through Osaka to Edo,” said Keisuke Yao, a professor of modern Japanese history at the University of Kitakyushu and an expert on the history of sugar distribution. “Sugar retailers were established in northern Kyushu 50 to 60 years earlier than in Edo.”
Nagasaki Kaido was known as a “sugar road.” So-called Nanban-gashi — sweets from European countries such as kasutera sponge cake and maruboro round cake — were produced along it for centuries.
According to Yao, about 3,000 tons of sugar were imported annually in the middle of the Edo period. Of that, 5 percent to 10 percent went to Nagasaki, Saga and Fukuoka prefectures. Assuming Nagasaki’s population was 50,000 and Edo’s was 1 million, annual sugar consumption was three kilograms per Nagasaki resident and just 900 grams for Edo residents.
“Sugar was easy to come by in northern Kyushu because of Nagasaki, a center for international trade,” Yao said.
A childcare survey conducted in the early years of the Showa era (1926-1989) found that residents of Fukuoka Prefecture used syrup and sugar-added rice as substitutes for breast milk. More examples from Kyushu included sugar water in Kumamoto Prefecture and roasted sticky rice with added sugar in Miyazaki Prefecture.
“Childcare techniques tend to maintain old customs that are passed down from older generations,” Nagaoka said. “Therefore, it is highly likely that sugar and syrup were also used for baby and infant [foods] in the Edo period.”
Nagaoka pointed out that even today, Kyushu residents prefer sweeter flavors — soy sauce is a typical example — compared to Kanto residents.
“It is likely that the local food culture, which was rich in sugar, caused the teeth of children [in Kyushu] to decay [during the Edo period],” Nagaoka said.
Nagaoka’s study also found that the upper teeth were more prone to decay than the lower ones. In Edo children across all the age groups, decay in the the upper teeth was more prevalent. The average figures were 17.5 percent for the upper teeth and 5.6 percent for the lower ones. It is believed the higher percentage is because children found it more difficult to properly brush their upper teeth.