Abstract
The composition of nine essential amino acids in vegetable foods is different from that in meat. We drew graphs comparing the composition in a food with the FAO/WHO/UNU reference pattern (1985), an ideal composition for protein nutrition. In constructing the graphs, we used the ratio of each amino acid's content to the geometric mean of the nine amino acids'contents in a food. A glance at the graphs shows the extent to which the relative quantity of each amino acid in a given vegetable food is lower or higher than the reference. We found that chestnuts, squash and potatoes have a composition close to the reference, thus showing a high protein quality. This fact suggests that the chestnuts which were eaten by the Jomon people in Sannai Maruyama, north-east Japan, from 3500 to 2000 BCE, the squash eaten by the Aztecs in Central America to the 16th century A.D., and the potatoes eaten by the Incas in South America to the 16th century A.D. constituted not only an energy source but also an important protein source.
