From Iodized Salt to Folic Acid Flour: The Fortification Story
The earliest program in this story is iodized salt, which Michigan grocers began stocking in 1924. Enriched bread, vitamin D milk and folic acid flour followed, and each answered a different public health problem.
The earliest program in this story is iodized salt, which Michigan grocers began stocking on May 1, 1924. Enriched bread, vitamin D milk and folic acid flour followed, and each answered a different public health problem. ## Iodized salt went on grocers' shelves in 1924 In 1922, David Murray Cowie, a pediatrician at the University of Michigan, read a Swiss report that proposed adding iodide to table salt. Iodine deficiency was common around the Great Lakes, a region known as the goiter belt, and Cowie reasoned that everyone ate salt every day ([DOI](https://doi.org/10.1111/1468-0009.12064)). The stakes were visible. In 1918, an examining physician for a Houghton County, Michigan, draft board rejected nearly 30% of potential Army recruits because of goiters and hypothyroidism. Cowie then spent about two more years persuading salt makers and doctors. A Michigan State Medical Society referendum endorsed iodized salt, and on May 1, 1924, the first boxes reached grocers' shelves in the state. The surprise is who made them: the salt manufacturers voluntarily produced every box, and no laws or regulations were required ([DOI](https://doi.org/10.1111/1468-0009.12064)). Within months, more than 90% of the table salt sold in Michigan was iodized. Later that year, the Morton Salt Company of Chicago distributed iodized salt nationally, and other US salt makers followed. By 1935, goiter in Michigan had dropped by 74% to 90%, with the biggest drops among children who had used iodized salt continuously for at least six months ([DOI](https://doi.org/10.1111/1468-0009.12064)). Iodized salt is still the most widely used strategy against iodine deficiency, according to the [NIH Office of Dietary Supplements](https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/). In the United States, though, most salt intake comes from processed foods, and food makers almost always use noniodized salt in them. The household shaker is only part of the picture. ## Enrichment put back what milling took out Modern flour refining had stripped bread of its natural vitamins and minerals. In 1941, the National Nutrition Conference for Defense supported "enrichment" programs to restore foods to their natural levels of nutrients, as an immediate solution, according to the Science History Institute. Flour enrichment had started in the late 1930s, when thiamine and niacin became available in bulk through industrial synthesis, and the milling industry adopted it largely by voluntary cooperation. The War Food Administration made it mandatory in 1943. The institute also notes that the federal government distinguished enrichment, which restored nutrients lost in processing, from fortification, which added vitamins to almost any product. Milk came next. Vitamin D-fortified milk appeared in the early 1930s, mostly by irradiating milk with ultraviolet light rather than adding bulk vitamins. Kellogg's Pep, a breakfast cereal with added vitamins D and B1, followed in 1938 ([Science History Institute](https://www.sciencehistory.org/stories/magazine/vitamins-come-to-dinner/)). ## Folic acid joined the flour story in 1998 Folic acid, the form of folate used in fortified foods and most supplements, had evidence behind it before the rule. In the Medical Research Council Vitamin Study, folic acid taken before pregnancy protected women at high risk of an affected pregnancy. Of 1,195 women with completed pregnancies, the folic acid groups had 6 neural tube defects against 21 in the other groups, a 72% protective effect (relative risk 0.28; 95% CI 0.12 to 0.71), according to PubMed ([PubMed](https://pubmed.ncbi.nlm.nih.gov/1677062/)). The federal response followed the Public Health Service's advice that women of childbearing age consume 400 micrograms of folic acid daily. A March 1996 Federal Register notice described the rulemakings FDA was carrying out to implement that advice, including one "to require the addition of folic acid to certain standardized cereal-grains" ([Federal Register, 61 FR 8797](https://www.govinfo.gov/content/pkg/FR-1996-03-05/html/96-5012.htm)). The requirement took effect in January 1998. The NIH Office of Dietary Supplements says FDA began requiring manufacturers to add 140 mcg of folic acid per 100 grams to enriched breads, cereals, flours, cornmeals, pastas, rice and other grain products. The program raised mean folic acid intake by about 190 mcg a day ([NIH ODS](https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/)). Our [folate history](/blog/history/history-of-folate-from-lucy-wills-to-fortified-bread) covers the research that came before the rule. ## What fortification means for supplement planning Fortified food and supplements add to the same totals, which is the planning problem. The adult upper limit for folic acid is 1,000 mcg a day. About 5% of men and women aged 51 to 70, and men aged 71 and older, exceed it, primarily because of supplements ([NIH ODS](https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/)). Iodine works the same way. The adult upper limit is 1,100 mcg a day. In NHANES data from 1999 to 2004, 28% to 29% of adults used iodine-containing supplements, which adds to total iodine intake ([NIH ODS](https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/)). If you are weighing a magnesium supplement, our [magnesium monograph](/ingredients/magnesium) covers the forms. Our [vitamin D complete guide](/health/vitamin-d-complete-guide) covers the vitamin that went into milk in the 1930s. ## Bottom line Fortification works on whole populations, and a supplement works on the person who takes it. Read the label on fortified food and any supplement together, and add up the folic acid and iodine from both before you buy a new product. ## Frequently asked questions ### Why did governments start adding nutrients to food? Goiter was common in the goiter belt, and refining had stripped bread of natural vitamins and minerals. Iodized salt answered the first problem in 1924, and enrichment answered the second in the 1940s, according to the Science History Institute and the Milbank Quarterly. ### When did iodized salt first appear in the United States? The first boxes reached grocers' shelves in Michigan on May 1, 1924. Morton Salt of Chicago then distributed iodized salt nationally, later that year ([DOI](https://doi.org/10.1111/1468-0009.12064)). ### Why was enriched bread a wartime measure? The 1941 National Nutrition Conference for Defense backed enrichment as an immediate fix for the inadequacies of the American diet. The War Food Administration mandated it in 1943, after the milling industry had largely adopted it voluntarily, according to the Science History Institute. ### How did vitamin D get into milk? Mostly by irradiation. Vitamin D-fortified milk appeared in the early 1930s, when milk was exposed to ultraviolet light rather than given bulk vitamins, according to the Science History Institute. ### When did folic acid enter the flour story, and why? FDA began requiring folic acid in enriched grain products in January 1998, to reduce the risk of neural tube defects. The Medical Research Council Vitamin Study supplied key evidence in 1991 ([PubMed](https://pubmed.ncbi.nlm.nih.gov/1677062/)), and the Public Health Service had recommended 400 micrograms a day for women of childbearing age. ### How much do fortified foods contribute to intake today? The grain program raised mean folic acid intake by about 190 mcg a day, according to the NIH Office of Dietary Supplements. For iodine, most US salt intake comes from processed foods, which almost always use noniodized salt, so iodized salt supplies only part of the total. ### What does fortification mean for supplement planning? Count the folic acid and iodine from fortified food, supplements and iodized salt together. The NIH Office of Dietary Supplements sets adult upper limits at 1,000 mcg a day for folic acid and 1,100 mcg a day for iodine. ## Next reads - [Folate and Folic Acid: From 1930s Bombay to Fortified Bread](/blog/history/history-of-folate-from-lucy-wills-to-fortified-bread): the folate story behind the 1998 grain rule. - [Vitamin D complete guide](/health/vitamin-d-complete-guide): the vitamin D that went into milk in the 1930s. ### Related reading - [folic acid in the 1998 grain rule](/blog/history/history-of-folate-from-lucy-wills-to-fortified-bread) - [iodized salt in Michigan in 1924](/blog/history/history-of-iodine-from-seaweed-to-iodized-salt) - [the vitamin pills and enriched bread of the 1940s](/blog/history/history-of-the-multivitamin-from-wartime-pills-to-daily-habit)