Peanut butter, invented in 1890 as a meat protein substitute, is made from ground-up peanuts. Peanuts are not nuts at all, but legumes. Peanut butter offers a nutrient-rich addition to your snacks, meals and desserts.Peanut butter offers one convenient way to help boost your peanut intake and also has a nutritional profile that includes significant amounts of several beneficial nutrients. Some types of peanut butter contain additives, such as sugar, that lower the nutritional value of the food, however.