When used to assess the nutrient content of diets, recipes, or commercial food products, a nutrient database should provide a complete nutrient profile for each food in the database. Chemical analyses for a wide range of nutrients in the many foods included in a database are not always practical. Therefore, some nutrient values must be estimated. Common methods for estimating nutrient values include (1) using values from a different but similar food, (2) calculating values from different forms of the same food, (3) calculating values from other components in the same food, (4) calculating values from household recipes or commercial product formulations for multicomponent foods, ( 5) converting values from information on the nutrient label of a commercial food product, ( 6) calculating values from a product standard, and (7) assuming a zero value. Quality control procedures and nutrient validation programs should be implemented to verify that appropriate data selection, calculation methods, and data entry were used. Estimated nutrient values should be identified in the database. Some referencing systems also indicate the method used to derive each estimated value.