The problem of human nutrition in medieval natural philosophy was closely connected with metaphysical claims about the human soul. The human soul was considered to be ungenerable and incorruptible, since it is created by God and not naturally derived from the potency of matter. This raises a question about human nutrition: How can an immaterial soul be engaged in obviously material processes such as nutrition? This problem is particularly pressing for John Buridan (ca. 1300 -1358/60), who identifies nutritive powers with the soul; and since the human soul is immaterial, the human nutritive powers are immaterial as well. Though Buridan subscribes to the view that the process of nutrition involves the corruption of food and the partial substantial generation of the soul, he nevertheless believes that general features of nutrition can be explained for human beings. I argue that Buridan conceives of nutrition as a merely material change, a view which is in line with his broader conception of substantial generation and the relation between a substantial form and its coming to existence in suitably disposed matter. Ultimately, the way in which Buridan accounts for nutrition turns out to be another example of a rising dualism between body and soul, pointing to developments some centuries later which will render substantial forms superfluous.