E621, also known as monosodium glutamate (MSG), is a flavor enhancer commonly used in food products. It is derived from glutamic acid, an amino acid found naturally in many foods, including tomatoes and cheese. E621 is often added to savory dishes, snacks, and processed foods to enhance their umami flavor, which is one of the five basic tastes. While E621 is generally recognized as safe by food safety authorities, some individuals may experience sensitivity or allergic reactions to it. This has led to ongoing debates about its health effects, prompting some consumers to seek out products labeled as "MSG-free."