The results of this study provide a method for accurately estimating the nutritional value of cooked food in nutrition investigations and during menu preparation. Vegetable products in the “Standard Tables of Food Composition in Japan, Fifth Revised Edition” were categorized by food group, method of cooking, and other factors. The rate of change of each element in each food group due to cooking by various methods was examined. The rates of element change by cooking in vegetable products could be divided into 28 levels. Differences in the rates of element change by cooking were apparent between the groups, even within the same food group. These rates of element change by cooking enable the nutritional value of food after cooking to be accurately calculated, even for those elements with no nutritional value.
