[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 element (Minerals) in each food group due to cooking by various methods was examined. [Results] 27 kinds of the rates of element change were found to be useful for therapeutic diets. The rates of element change by cooking in vegetable products could be divided into 32 levels. The rates of element change by cooking in animal products could be divided into 17 levels. We were found to be useful for nutritional calculations diet. Differences in the rates of element 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 nutritional components that remain after cooking. It is therefore possible to compute the amount of nutritional components for cooked food with no nutritional component value. This improves the accuracy for calculating the nutritional value in nutritional assessment and menu preparation.