[Objective] The aim of this study is to provide an accurate method for assessing nutrient contents to aid nutritional surveillance and menu preparation. [Methods] Vegetable products and animal products in the "Standard Tables of Food Composition Japan -2010-" were categorized by food group, method of cooking, and other factors. The rate of change of each vitamin in each food group due to cooking by various methods was examined. [Results] The rates of element change by cooking in vegetable products could be divided into 32 kinds. The rates of element change by cooking in animal products could be divided into 17 levels. Twenty-five kinds of the rates of vitamin change were found to be useful for therapeutic diets. Differences in the rates of vitamin change by cooking were apparent between the groups, even within the same food group. [Conclusions] The evaluated rates of component change by cooking can be used for estimating the amount of vitamin that remain after cooking. It is therefore possible to compute the amount of vitamin for cooked food with no vitamin component value. This improves the accuracy for calculating the vitamin in nutritional assessment and menu preparation.