Some proteins, particularly those extracted from milk or egg whites, directly address the brain without following the full “metabolic” route: after being digested in the stomach, these proteins enter the first part of the intestine as small peptides. They then alert the brain. These peptides trigger intestinal gluconeogenesis (i.e. the intestine cells make glucose without carbohydrates). They then go through the portal vein, the vein that “nourishes” the liver – all nutrients absorbed by the digestive track go through the liver by the portal vein –, and saturate the mu-opioid receptors, identical to those in the brain, implicated in morphine addiction. They therefore have an appetite-suppressing effect that lasts a few hours: this is the “satiety” effect that prevents us from getting hungry between meals. As all this takes about 20 minutes, no meal should ever last less than this. The proteins influence our appetite at the next meal. The triggering of this process may take 20 minutes, but it then lasts several hours.