Enrichment of wheat flour refers to the addition of select vitamins and minerals to refined flours, to supplement the loss of micronutrients that occurs during the refining process. Generally the requisite additions are thiamin, riboflavin, niacin, folic acid, iron, and possibly added calcium. Where this is practiced, it is typically strictly regulated and mandated by law.
The iron in enriched flours has been found to become less available for absorption following baking.
Whole wheat, whole grain flours are typically exempt from this regulation as they retain the micronutrients present in the wheat germ and bran.