Heme is an iron-containing molecule that occurs naturally in every single plant and animal. It’s an essential molecular building block of life. Heme gives your blood its ability to carry oxygen. It’s found in all living organisms, and it's been consumed every day—heck, every second—for hundreds of thousands of years.
Heme is super abundant in animal muscle, and that's what makes a burger so flavorful. It's also why meat is a particularly good source of iron. The heme found in animal muscle is carried by a protein called myoglobin.
Plants, particularly nitrogen-fixing plants and legumes, also have heme. The heme found in these plants is carried by leghemoglobin, which is closely related to myoglobin. Leghemoglobin in the soy plant is called soy leghemoglobin. The heme molecule in plant-based heme is atom-for-atom identical to the heme molecule found in meat. It’s what makes the Impossible Burger so rich and decadent.