Dictionary.net

Any food that has been supplemented with essential nutrients either in quantities that are greater than those present normally, or which are not present in the fortified food. The supplementation of cereals with iron and vitamins is an example of fortified food. Fortified food includes also enriched food to which various nutrients have been added to compensate for those essential nutrients removed by refinement or processing. (From Segen, Dictionary of Modern Medicine, 1992)