Final answer:
The micronutrient acid added to flour in the U.S. since the 1900s is folic acid, which is crucial for preventing birth defects and promoting overall health. Food fortification, which includes adding essential nutrients to common foods, has a historical basis in ensuring food safety and enhancing nutrition.
Step-by-step explanation:
The micronutrient acid that has been added to flour in the U.S. since the 1900s is folic acid. This fortification is to prevent certain birth defects and to contribute to overall public health. The importance of food fortification can be traced back to concerns about food safety, as highlighted by Friedrich Accum in the early 19th century.
While Accum's focus was on preventing the harmful practice of food adulteration, modern fortification efforts are geared toward nutritional enrichment. For example, ingredients like wheat flour can be enriched with various micronutrients such as niacin, reduced iron, thiamine mononitrate, riboflavin, and folic acid, which are essential for maintaining health. Notably, the addition of iodine to salt, which began in the early 1900s, has had a significant impact on preventing iodine deficiency, similar to the fortification of flour with folic acid and other nutrients.