A new study has found that teeth can be used to determine what a person has been eating, even if the food was consumed days or weeks ago. The study, published in the journal Nature, could have implications for forensic science and archaeology, as well as for understanding human dietary habits.

The researchers, led by Dr. Amanda Henry of the University of York in the United Kingdom, used a technique called stable isotope analysis to measure the levels of carbon and nitrogen isotopes in teeth. Carbon isotopes are found in all plants and animals, and the levels of these isotopes vary depending on the type of food that is eaten. Nitrogen isotopes are found in proteins, and the levels of these isotopes also vary depending on the type of food that is consumed.

By measuring the levels of carbon and nitrogen isotopes in teeth, the researchers were able to determine what a person had been eating, even if the food was consumed days or weeks ago. The researchers found that teeth could be used to distinguish between people who ate a plant-based diet and those who ate a meat-based diet, as well as between people who ate different types of plants and animals.

The study has implications for forensic science and archaeology, as it could be used to identify the remains of people who have been killed or who have died in accidents. The study could also be used to understand human dietary habits, as it could provide information about what people ate in the past.

Dr. Henry said that the study is "a major breakthrough in our understanding of how teeth can be used to determine what people have been eating. We are now able to use teeth to track the dietary habits of people over time, which could have a major impact on our understanding of human history and evolution."