Walnut is a single-seeded fruit grown from the walnut tree and is a beneficial source of fat, fiber and protein. Trees of this fruit are found in the Northeast of North America, and are now grown in China, Iran, and the United States, as well as in California and Arizona. Walnuts are available both raw and roasted and salted or salted. This rich food contains manganese, copper, magnesium, phosphorus, vitamin B6 and iron.