There were three groups of participants in the research: a fasting control group (they ate nothing), a group (iso control group) that had carbohydrates with milk protein (same calories as the amino acid shake) and the group that had the amino acid mixture. (fitnessandpower.com)
Other studies have found that a breakfast of low - glycemic - index foods like oatmeal increased mental acuity over high - glycemic - index breakfasts with the same number of same calories. (health.com)