@alisha-- Coffee really does regulate bowel movements. I have a latte every morning with breakfast and I have to go twenty minutes later. It's like clockwork.
I'm not sure if it's the stimulants in the coffee though. I'm sure the stimulants have some effect, but I also feel like it might be the milk or creamer. Milk helps some people go, so that's highly possible and I know that some dry coffee creamers have ingredients in them that can have a laxative effect.
I think another reason that coffee promotes regularity is because it makes us drink more water. Coffee makes me very thirsty and I usually follow up with two to three glasses of water after a cup. Everyone knows that drinking enough water is the number one rule for regular bowel movements.