FDA and later led the laboratories of Good Housekeeping Magazine. During World War I the Progressives' moral advice about food conservation was emphasized in large-scale state and federal programs designed to educate housewives. Large-scale foreign aid during and after the war brought American standards to Europe. From 1912 to the end of the 1930s researchers discovered and popularized the role of various vitamins and minerals in human health. Starting with iodized salt in 1924, commercially distributed food began to be fortified with vitamins and minerals. In 1932, milk began to be fortified with viosterol, a purified vitamin D2 product. Synthetic thiamin (vitamin B1) first became available after 1936 and bakers began voluntarily enriching bread with high-vitamin yeast or synthetic vitamins in the late 1930s. The Food and Nutrition Board of the National Academy of Science established the first set of "Recommended Dietary Allowances" in 1941. In 1943, the US War Foods Administration issued the War Food Order No. 1, which made enriched bread the temporary law of the land. In 1945 George Stigler published an article on "The cost of subsistence" which described the so-called Stigler diet, his solution to the problem of providing a diet that met the RDA at a minimum cost. The logistical requirements of the US military during WW2 and the Korean War spurred the development and growth of the processed foods industry in the US. These wars encouraged production of shelf-stable ingredients processed on a vast industrial scale. Examples include powdered milk, powdered eggs, potato flakes, and frozen concentrated orange juice. After the war, low-cost, highly processed foods became one of the foundational elements of an era of mass prosperity. Many companies in the American food industry developed new products requiring minimal preparation, such as frozen entrees. One such example is the TV dinner in which a multi-course meal was assembled in aluminum packaging in a food factory and flash frozen, then reheated at home in a thermal oven to be served while watching TV. Convenience foods of the era were designed to simplify home preparation. One example is macaroni & cheese created using a powdered artificial cheese product that is reconstituted at home with fresh milk. Newspapers and magazines ran recipe columns, aided by research from corporate kitchens, which were major food manufacturers like General Mills, Campbell's, and Kraft Foods. For example, the General Mills Betty Crocker's Cookbook, first published in 1950, was a