It appears your best bet is to eat protein or fat, avoiding sugars and other simple carbohydrates:
Similarly to insulin, you don’t want cortisol levels to be more elevated than they should naturally be. Natural levels being those experienced by our hominid ancestors on a regular basis. You need cortisol, but you don’t need too much of it. Many tissues in the body become resistant to hormones that are more elevated than they should be, like insulin and leptin, and this is also true for cortisol. It is a bit like people constantly shouting in your ears; after a while you cover your ears, or they get damaged, so people have to shout louder. If you frequently have acute elevations of cortisol levels, they may become chronically elevated due to cortisol resistance.
Chronically elevated cortisol levels are associated with the metabolic syndrome, the hallmark of the degenerative diseases of civilization.
Stress causes elevated cortisol levels. And those levels are significantly elevated if you consume foods that lead to a high blood glucose response after a meal. That is what an interesting experimental study by Gonzalez-Bono and colleagues (2002) suggests. The full reference and link to the study are at the end of this post. They used glucose, but we can reasonably conclude based on glucose metabolism research that foods rich in refined carbohydrates and sugars would have a very similar effect. If we think about the typical American breakfast, possibly even a stronger effect.
In order to do their study they needed to put the participants under stress. *To cause stress the researchers did what many college professors have their students do at the end of the semester, which is also something that trial lawyers and preachers are good at, and something that most people hate doing. You guessed it. *The researchers had their subjects do, essentially, some public speaking. The experimental task they used was a variation of the “Trier Social Stress Test” (TSST). The researchers asked the participants to conduct a 5-minute speech task and a 5-minute mental arithmetic task in front of an audience.
The participants were 37 healthy men who fasted for at least 8 h prior to the study. They were randomly assigned to one of four groups. The glucose group consumed 75 g of glucose dissolved in water. The fat group consumed 200 g of avocado. The protein group drank 83 g of proteins dissolved in water. The fourth group, the water group, drank plain water.
The results? The glucose group had nearly double the cortisol response of the fat, protein, and water groups, which didn't differ significantly. The lesson? If you have a stressful event on your calendar, forego the conventional "healthy breakfast" of fruit and cereal for some sausage, eggs, avocado, or other protein- and fat-rich foods.
(via Health Correlator)