Walnut, from the Juglans regia tree, is a nutrient-rich and beneficial nut, containing fiber, omega-3, and minerals. Walnuts are widely spread, and despite being originally from the Middle Eastern region (Caucasus, Armenia, Iran, up to the Himalayan mountains), they are also considered a typical plant of the Italian peninsula. This tree grows in isolation because its leaves release a substance called juglone that can harm or even kill surrounding plants.