In the southern United States in the 1800s, geophagia was a common practice among the slave population.  Geophagia is a form of pica in which the person consumes earthly substances such as clay , and is particularly prevalent to augment a mineral-deficient diet.  Noteworthy is the fact that Kaolin was consumed by west Africans enslaved in the South-eastern United States, particularly the Georgia belt, due to the anti-diarrheal qualities in the treatment of dysentery and other abdominal ailments.  The practice of consuming Kaolin rocks was thereafter studied scientifically, the results of which led to the subsequent pharmaceutical commercialization of Kaolinite, the clay mineral contained in Kaolin. Kaolinite became the active ingredient in drugs like Kaopectate and Pepto-Bismol, although the formulations have since found additional active ingredients to replace Kaolinite. 
The brain stem can control food intake, because it contains neural circuits that detect hunger and satiety signals from other parts of the body.  The brain stem’s involvement of food intake has been researched using rats. Rats that have had the motor neurons in the brain stem disconnected from the neural circuits of the cerebral hemispheres (decerebration), are unable to approach and eat food.  Instead they have to obtain their food in a liquid form. This research shows that the brain stem does in fact play a role in eating.