Enriched flour is white flour with added nutrients intended to compensate for the loss of natural nutrients that occurs during processing. Each pound (0.45 kg) of flour must contain the following nutrients in order to be considered enriched according to the United States Food and Drug Administration (FDA) guidelines: 2.9 milligrams of thiamine, 24 milligrams of niacin, 0.7 milligrams of folic acid, 1.8 milligrams of riboflavin, and 20 milligrams of iron. Except for iron, all of these nutrients are B vitamins.
Some enriched flours also contain 960 milligrams or more of calcium per pound. Though some people refer to enriched flour as fortified flour, that term is not correct, because fortified implies the addition of nutrients that never existed in the food.
White flour first became popular during the medieval period in Europe, when it was perceived as cleaner and healthier than untreated flour. This may have been because the processing necessary to make white flour kills fungus, though people at the time would not have been aware of this feature. White flour remains more popular than other types of flour in the Western world, especially for baking. However, compared to darker flours, white flour lacks many essential nutrients. Enriched flour combines the flavor and texture of white flour with the nutrients found naturally in untreated flour.
Chemist Benjamin R. Jacobs was the first to discover the nutritional deficiencies of white flour and to suggest ways to correct the problem in the 1920s. During World War II, Jacobs' methods were widely promoted in Great Britain and the United States. Enriched flour offered a way to ensure that citizens of all social classes were eating nutritious diets despite rationing. In 1942, the United States Army announced that it would only use enriched flour, making the product immensely popular among United States civilians who wished to show their support of the troops. Today, enriched flour remains the most popular type of flour in the United States.