Carbon and nitrogen stable isotope ratios of diet of the Japanese and diet-hair offset values.

The stable isotope ratios of carbon and nitrogen (C and N) were measured in composite samples of Japanese food and hair. Three hundred eighty-nine foodstuffs were collected in Tokyo and Gunma Prefecture, Japan, in 2020. The foodstuffs were classified into 15 food categories, prepared as usually consumed, and mixed to make 15 composite samples representing each of the food categories.