Final answer:
The refined grain products are not required by legislation to have potassium added to them, unlike folate, iron, thiamin, and riboflavin.
Step-by-step explanation:
Legislation requires that a variety of nutrients be added back to refined grain products to replace those lost during processing. Among the nutrients that must be added are folate, iron, thiamin, and riboflavin. The item that is not required to be added to refined grain products is potassium. This is in accordance with the U.S. federal regulations designed to prevent deficiencies in these key nutrients after the refinement process.