White flour became adopted in many cultures because it was thought to be healthier than dark flours during the late Middle Ages. As white flour was more expensive it became a fashionable indicator of perceived social status and tended to be consumed mostly by the richer classes. Another factor was that
mold and
fungus in the grains, which led to several diseases, were significantly reduced in the processing that resulted in white flour. In the 1920s,
Benjamin R. Jacobs began to document the loss of essential nutrients, however, through this processing of
cereals and
grains and to demonstrate a method by which the end products could be enriched with some of the lost nutrients. These nutrients promote good health and help to prevent some diseases. Enrichment was not possible until 1936, when the synthesis of
thiamine was elucidated. The decision to choose flour for enrichment was based on its commonality in the diets of those wartime populations, ranging from the rich to the poor. These wartime campaigns resulted in 40% of flour being enriched by 1942. In February 1942, the U.S. Army announced that it would purchase only enriched flour. This resulted in a large expansion of enrichment, but smaller local mills were still selling cheap, unenriched flour that could end up consumed by the poor, who needed enrichment the most. In 1943, the War Foods Administration issued a temporary ban on non-enriched bread, finally raising enrichment compliance to 100%. == Enrichment requirements ==