Chris Kresser: It’s meant to affect a normal day, but caffeine has a rather immediate effect and so it’s recommended to stop caffeine, not to do caffeine during the test procedure for that reason. Decaf should not affect DUTCH and neither should a small piece of dark chocolate. As many of you probably know, there’s a debate over whether chocolate actually contains caffeine or a caffeine-like compound, and it has a very different effect in different people. Some people it’s quite stimulating, and in others it doesn’t have that effect at all. You can eat it right before bed and not be affected.