Well, make sure it isn't Jiffy Peanut Butter, LOL

Buy Adam's or freshly ground kind that has no sugar added. I don't remember seeing it on the list of allowed foods, but I have had a teaspoon of it once in a while outside my RM and nothing has happened. However, that is my body and I couldn't tell you if yours will react the same way. I guess it is all really trial and error.