The Path Food Takes Through the Digestive Tract

This article follows the path that food takes through the digestive tract from the first smell, mention of food, or sight of food through to the elimination of food from the body. The time it takes for food to traverse the digestive tract or gastrointestinal tract is referred to as transit time. Transit time can vary greatly from one person to another but typically ranges from 24 to 72 hours. Transit time can be affected by several things such as diet composition, illnesses, medications, physical activity, and even emotions. (Grosvenor & Smolin 2006)

The gastrointestinal tract begins in the mouth at the first smell, mention, or sight of food, stimulating salivary glands to excrete saliva. The tongue positions, saliva moistens, and teeth chew food, forming what is called a bolus and then moving the bolus into the pharynx. The bolus then enters the esophagus, part of the gastrointestinal tract responsible for transporting food from mouth to stomach in a process known as peristalsis or involuntary muscle contractions. (Grosvenor & Smolin 2006)

In the stomach, the bolus mixes with acid, partially digesting and turning it into a partial liquid otherwise known as chyme; the stomach wall has three layers of muscle which facilitate this process. Chyme typically empties from the stomach in two to six hours depending on the composition of foods eaten. Liquids empty from the stomach the fastest, followed by carbohydrates, proteins, and finally fats. Very little is absorbed in the stomach. (Grosvenor & Smolin 2006)

The small intestine, which is divided into three sections: the duodenum, the jejunum, and the ileum, is where the majority of nutrients are absorbed. Chyme passes from stomach to small intestine aided by the gallbladder, liver, and pancreas. The liver makes and secretes bile into the gallbladder where it is stored until it is needed; bile is necessary to digest and use fat. The pancreas then releases enzymes and bicarbonate into the small intestine neutralizing the stomach acid. (Grosvenor & Smolin 2006)

What is not absorbed in the small intestine passes through a sphincter into the large intestine, which includes the colon and rectum. The peristalsis is slower in the large intestine permitting the growth of bacteria which assists in breaking down fiber and absorbing some Vitamins. The colon absorbs water, vitamins and minerals not absorbed by the small intestine. What has not been absorbed by the digestive process is eliminated from the body via the rectum and anus. (Grosvenor & Smolin 2006)

One can test the transit time or the amount of time food stays in the digestive tract by eating beets or taking 4 charcoal capsules. Both beets and charcoal are harmless to the body and can be easily seen in the stool once its journey through the digestive tract has been completed. Whichever method is chosen, the time and date of the meal must be recorded. Do not consume any charcoal, beets, iron supplements, or other substance that may color stool for at least five days. Observe and record every stool for black or gray stools with charcoal and red stools with beets for five days. After five days have passed with no charcoal or beet color in the stool, the test may be repeated. Typically three tests are required to report the results to the doctor.

References

Grosvenor, M. B., & Smolin, L. A. (2006). Nutrition: Everyday choices. New Jersey: John Wiley & Sons, Inc.