[Objective] The aim of this study is to provide a more suitable method for assessing nutrient contents to aid nutritional assessment 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 component change (weight, energy, general components, fatty acids, cholesterol, dietary fiber, nitrate ion) in each group according to various cooking by methods was examined.

[Results] The rates of component change through cooking in vegetable products could be divided into 32 groups. The rates of component change through cooking in animal products could be divided into 17 groups. Differences in the rates of component change through cooking were apparent between the groups, even within the same food group.

[Conclusions] The rates of component (weight, energy, general components, fatty acids, cholesterol, dietary fiber, nitrate ion) change in 29 groups were found to be useful for therapeutic diets. The evaluated rates of component change through cooking can be used for estimating the amount of nutritional components that remain after cooking. Therefore it is 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.