How long does it take?

I am keeping a food diary to see which foods could be causing lower abdominal soreness or pain, doc thinks it might be from wheat. However I am not sure if the food you eat that same day is the food that is the problem or the food the day before. So my question is how don't does it take for food to get to that area? Any help would be very much appreciated!

http://www.mayoclinic.com/health/digestive-system/an00896

Thank you, thank you, I appreciate it! That helps so much!