The fruiting body is the actual mushroom. This is the typical structure that protrudes above ground, which is the actual mushroom, and where the most beneficial compounds live. Many companies use mycelium roots grown on other substrates like rice or grain, and the actual mushroom doesn’t even have a chance to form. They are then ground up with the grain and powderized, and therefore your mushroom supplement ends up being more starch than mushroom. There’s nothing wrong with mycelium...mycelium is amazing for the soil, the plants and for our world. But the fruiting body is what contains the most beneficial compounds for humans!