The U.S. Department of Agriculture produces a large comprehensive database that is used as a basis for most nutritional analysis software systems. The current version, the USDA Nutrient Database for Standard Reference, Version 13, contains 6200 foods and 82 nutrients. The database is updated approximately every two years. The nutrient values are usually averages of several chemically analyzed samples of foods. Some manufacturer's data is included. When possible, when data is missing for certain nutrients, imputing from other sources is done.
There are many computerized nutrient analysis systems available for computers. Some systems used for research cost up to $3000 while others can be obtained free of charge. The basis of the program is the ability to enter foods as eaten and produce an analysis of nutrient intakes by day or week. Many food items in nutrient databases are represented in the edible form, for example peeled potato (as opposed to whole potatoes) or braised beef (as opposed to raw). The nutrient values do not represent the bioavailability of the nutrient in that food. /PARAGRAPH PARAGRAPH Different computer programs are designed for use by the consumer, an interviewer, or researcher. When selecting nutrient analysis software, several factors should be considered. Such factors include the source of the data, size and comprehensiveness of the nutrient database, number of nutrients, method used to impute for missing data, timeliness of updates, and ease of use. /PARAGRAPH