Intestinal transit time refers to how long it takes for food to move from the stomach to the anus after it has been broken down in the stomach. Rapid Intestinal Transit results in inadequate nutrient absorbtion. The time taken for food to pass through the gastrointestinal tract depends on various factors. It normally takes around 2.5 to 3 hours for 50% of stomach contents to empty into the intestines, and 4 to 5 hours for the stomach to empty completely. A 50% emptying of the small intestine then takes another 2.5 to 3 hours, and the final stage – transit through the colon – normally takes 16-40 hours. High-fiber diets generally result in lower transit times.
Rapid intestinal transit is often suspected when stool color is green(ish), meaning that the final stages of digestion have not had time to take place.
A green or greenish stool is usually due to rapid transit of food through the intestines. Bile is green and gradually changes to brown through the digestive process, which takes time. If the food is moving too fast, there is not enough time for this chemical change to take place.
Rapid passage (or transit) of stool is one of the most common causes of diarrhea. Stool that leaves the large intestine too quickly is watery: there is not enough time for fluid and nutrients to be absorbed from the contents of the gastrointestinal tract.
If food passes through the intestine too rapidly (for example due to reduced length), there is not enough time for proper digestion and absorption to be completed.