Japanese researchers discovered that people in cities during the Edo and Meiji periods ate food with more minerals than modern diets. The team studied hair samples from old books published between the 17th and 19th centuries. During the Edo period, waste paper was collected and reused for book covers. Hair often got mixed into the recycled paper. Scientists from Ryukoku University examined hair from about 400 books.
The hair contained higher levels of essential minerals like potassium, calcium, iron and copper compared to modern people. However, zinc levels were lower because people ate less pork. The research showed that people relied heavily on rice and sea fish for their meals. Over time, potassium declined as people switched from brown rice to white rice. Professor Maruyama said Edo-period meals were simple but healthier in some ways. The findings offer clues about what people should eat to get enough minerals today.