Food distributed to consumers through a distribution chain may be traced by tagging the food with DNA tags that identify the origin of the food, such as the grower, packer and other points of distribution, and their attributes. This makes it much quicker and easier to trace the food in case of food contamination or adulteration. Preferably these attributes indicate the field, location, crew and machine used to grow and process the food, and the dates of the various steps of food harvesting, processing and distribution. Natural or synthetic DNA pieces may be used to tag items, including food items. Multidigit binary or other types of bar codes may be represented by multiple types of DNA. Each digit of the bar code may be represented by one, two or more unique DNA pieces.