Japanese historical study finds Edo and Meiji era diets richer in minerals

Researchers from Ryukoku University, the National Institute of Japanese Literature, and other institutions have discovered that urban commoners during Japan’s Edo (1603–1867) and Meiji (1868–1912) periods consumed diets richer in certain minerals than modern populations.

The study, published in the journal Scientific Reports, utilized hair samples found in recycled paper from approximately 400 historical books. Because waste paper was frequently reused for book covers during the Edo period, researchers were able to extract hair presumed to belong to ordinary residents of cities such as Tokyo, Kyoto, and Osaka.

Using particle-induced X-ray emission and stable isotope analyses, the team found higher concentrations of essential minerals—including chlorine, potassium, calcium, manganese, iron, and copper—in historical samples compared to modern ones. Conversely, zinc levels, which are abundant in pork, were lower. Isotope analyses suggest these historical diets relied heavily on rice and sea fish. The decline in potassium and silicon levels over time coincided with the transition from brown rice to milled white rice.