Hair Analysis Finds Japan Edo-Era Diet Richer in Minerals than Modern Diet

A Ryukoku University-led team of researchers has discovered that the Edo period (1603-1867) diet contained higher mineral levels than contemporary diets. The team analyzed hair found within the covers of traditional Japanese books, which were made from recycled paper. The hair analysis revealed that Edo-era individuals consumed diets high in minerals, primarily due to a diet centered on brown rice and fish.

The research team examined about 70,000 traditional Japanese books housed in their library, focusing on approximately 400 volumes published between the mid-17th century and late 19th century. These books contained hair embedded in the recycled paper covers. The hair samples were then analyzed for elemental composition, which showed that concentrations of calcium and iron, found abundantly in marine fish, were significantly higher than those found in modern populations of Tokyo, Osaka, and Kyoto.

Additionally, the study found that concentrations of potassium and silicon, which are abundant in brown rice, initially increased but gradually decreased over the 250-year period. This suggests that the consumption of polished white rice became more prevalent over time. The analysis also detected high levels of lead in the samples, which is believed to have been absorbed from cosmetic face powder.

Professor Atsushi Maruyama of Ryukoku University, a member of the research team, stated that their findings allowed for a scientific identification of aspects of daily life that were difficult to discern from written records. Professor Michifumi Isoda of the International Research Center for Japanese Studies emphasized that the study provided valuable insights into the transition from brown rice to white rice consumption and corroborates historical records describing the frequent consumption of seafood in Edo.