How long after you eat a meal does it take to affect your bowels? I have a person that continually can swear that he can eat a meal, then like 35 minutes later it caused him to have really bad diarrhea. I try to tell him it can't happen that fast.

Hi, . Hi, i suspect that the person you know is telling you the truth. The gastrocolic reflex occurs when food is eaten. The food stimulates peristalsis (contractions) of the gut to move food down the GI track. If the gastrocolic reflex is off kilter than the food can move through the gut too quickly and result in diarrhea. Irritable bowel syndrome can be one cause for this type of symptom. My guess is, that it is hard for you to imagine this because you probably have a normal gastrocolic reflex pattern.