Ancient dental calculus reveals diverse diets of Japanese commoners

What did ordinary people really eat in premodern Japan, beyond the dishes described in cookbooks and the bones discarded at urban waste pits? Reconstructing past diets at the level of individual food items is remarkably difficult. Traditional archaeological approaches and stable isotope analysis of human skeletons reveal broad dietary categories – such as reliance on marine fish and C3 plants. But they cannot show which specific taxa or tissues each person consumed, nor how access differed between social groups in a stratified society like premodern Japan.

A research team comprising researchers from the Graduate University for Advanced Studies (SOKENDAI), Aomori Public University, Kyushu University, and other institutions turned to an alternative source of evidence: ancient dental calculus, the hardened plaque that still adheres to the teeth of skeletal remains. Using palaeoproteomic methods on calculus from eight adult commoners buried in the Umeda cemetery, north of present‑day JR Osaka Station, they analyzed both bone collagen stable isotope ratios and food‑derived proteins entrapped in the calculus to reconstruct individual diets in premodern Osaka.

Stable carbon and nitrogen isotope ratios showed that these individuals had typical urban premodern diets based on terrestrial plants and marine resources. The real novelty came from the dental calculus proteomics. From the eight individuals, the researchers identified 38 dietary proteins from 17 taxa, including nine fish taxa, several terrestrial and marine mammals, and multiple plants. Red sea bream (Pagrus major) muscle proteins were detected in six of the eight individuals, indicating direct consumption of a fish that historical sources describe as a luxury item. Proteins from flatfishes such as tonguefish (Soleidae), still important in Kansai and Seto Inland Sea cuisine today, were also found.

In addition, proteins from salmonids – cold‑water fish that do not naturally inhabit Osaka Bay – were identified in some individuals. This result provides direct evidence that commoners consumed marine products transported over long distances, likely via the coastal shipping routes that linked Hokkaido and the Japan Sea coast to Osaka. Dental calculus from three individuals contained proteins from non‑human terrestrial mammals, supporting historical accounts that meat from wild quadrupeds was eaten under the guise of "medicinal meat" despite formal taboos. The team also detected proteins from cotton seeds, which are normally inedible but can be processed into cottonseed oil. This suggests that everyday oil products derived from cotton – widely cultivated around Osaka in the Edo period – were possible part of commoners' diets.

Taken together, these results show that even relatively poor urban commoners buried in the Umeda cemetery had access to an unexpectedly diverse range of foods, including luxury species and products from distant regions. The study highlights how Osaka's role as the "Kitchen of the Realm" – a major hub for the production, redistribution and trade of foodstuffs from across western Japan – translated into real dietary diversity at the level of ordinary city dwellers.

The authors emphasize that the eight individuals analyzed represent only a tiny fraction of the thousands of skeletons from Umeda cemetery and the hundreds of thousands of people who lived in Osaka during the premodern period. Future work applying dental calculus proteomics to samurai, rural communities with less developed food distribution, other cities such as Edo and Kyoto, and earlier phases of the premodern period will allow us to compare dietary diversity across status, region, and time. More broadly, the study illustrates that local food cultures – such as Kansai's long‑standing taste for sea bream and tonguefish – have roots extending back centuries, which can only be revealed by carefully analyzing irreplaceable cultural heritage materials like human bones and associated dental calculus.

Source:

The Graduate University for Advanced Studies, SOKENDAI

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