Digestive Health Part II – Food Transit

The main functions of the digestive and intestinal systems are to breakdown, digest, absorb, transform food nutrients into energy (assimilate) and process them out of our body. The overall digestive tract is a muscular tube of about 30 feet long coupled with a whole host of primary and secondary organs (i.e. liver/pancreas) as well.

Digestion process actually begins before the food is placed in your mouth. It begins with the first thought of food or smell of food! Your body sends signals to stimulate the stomach to start producing Hydrochloric Acid (stomach juice – HCl) to be ready for the food that is incoming.

As the food enters in the mouth, it mixes with saliva which contains Ptyalin (a form of carbohydrate enzyme containing amylase) dissolves food immediately and saliva provides lubrication. We produce about a quart and a half of saliva everyday!

Ever heard your mom telling you to chew well. It is now proven that chewing well does improve your digestion. In fact, there is a simple experiment you can do to convince yourself of the enzyme action in your mouth. Take a piece of cracker (even salty ones will work) and chew it until it becomes liquidy in your mouth before you swallow it. The taste of the cracker will change from plain or salty to sweet in the liquid form. This is because the amylase action taking place breaking the carbohydrate into sugar right in your mouth.

Esophagus is the conduit by which your partially broken down food is channeled by peristalsis into the stomach where most of the breaking down take place. In the stomach, food is mixed with hydrochloric acid (HCl) and pepsin (enzyme). The curd-like fluid at this point of digestion is called ‘chyme’. Chyme enters small intestines by way of the pyloric sphincter and the first part of the small intestine is known as the Duodenum.

See the illustration here to identify key components.

It is at the Duodenum where chyme is broken down further with the help of the Pancreas and Liver/Gallbladder. These organs are attached to Duodenum by the common bile duct. They dump in more enzymes (catalysts) and bile salts (fats) to help digest proteins, carbohydrates, and fats.

Pancreas double duties both for digestion (amylase) and hormones (insulin/glucagon). Pancreas produces Amylase (for carbohydrates), bicarbonates, Insulin and Glucagon. Liver is the largest organ in the body. Liver stores fats, carbohydrates, proteins, and vitamins. Contrary to a common mis-understanding, gallbladder does not produce bile but liver does. Bile is stored in the gallbladder and at the proper time, the bile is released from the gallbladder to digest fats. The liver also neutralizes poisons by acting as a blood filter. It has over 500 duties everyday. Clearly one of the key organs in our body (considered THE most important organ in Traditional Chinese Medicine), liver can also function with a great deal of it removed!

In the Small Intestines – The 2nd part of the small intestines after the Duodenum is called the Jejunum. The 3rd part is the Ileum. These 3 parts together absorb carbohydrates, proteins, and fats. The chyme is now broken further down into smaller “micro-nutrients”(carbohydrate turns into glucose and other forms of readily assimilable sugars; proteins into amino acids; and fats in triglycerides, triesters of glyceryl and any of several fatty acids) where they are absorbed into the blood stream via the villi.

Intestinal villi are tiny, vertical standing, finger-like epithelial lining of the intestinal wall. Each villus is approximately 0.5-1.6 (millimetres) in length and has many microvilli. Villi increase the internal surface area of the intestinal walls. Increased surface area allows for increased intestinal wall area that is available for maximum absorption. Increased absorptive area is useful because digested nutrients pass into the villi which is semi permeable between the intestinal walls and the blood vessels. The increased surface area in the villi maximizes the distance nutrient molecules has to travel to get into the blood stream for optimal absorbancy. The circulating blood then carries these nutrients away eventually into the left ventricle chamber of the heart for them to be pumped to and used by the rest of the body.

The small intestine ends at an important junction called the illeocecal valve. This valve controls mucous and exit of unused and potentially toxic micro-chyme into the large intestine (colon). The ileo-cecal valve is the gate keeper between these two important organs. It serves to preventing a back-flow of unused and potentially toxic material. Keeping toxins out of the small intestines is critical as you can imagine toxins being absorbed into our blood stream causing eventual havoc to our health. The illeocecal valve is located at the same area as your appendix.

The colon is a 5 to 6 foot long muscle designed to pull water from the waste material and recycle the water back into the bloodstream while compacting and moving the waste toxic material out of our body. There are 3 parts to the colon sections – Ascending, Transverse, and Descending. The descending colon empties into a “S” shaped area called the Sigmoid Colon. Fecal matter is formed for elimination throughout the entire colon and it is expelled out of the system via the rectum.

The colon houses over 700 species of bacteria, some of which are “friendly” bacteria. They produce vitamin B12, Biotin, Vitamin K, and keep healthy flora balance against harmful bacteria, virus, and fungus. It is absolutely important therefore to keep the fecal matters moved out of our colon system so that it does not cause any potential damage such as fissures, hemorrhoids, and polyps. Stagnant toxins in the water material will also be partially re-absorbed back into our body thus compromising your immune system. Keeping a healthy colon bacterial environment is therefore critical to our health. More on that later.

Proper transit time for food to traverse from your mouth to rectum is anywhere between 24 to 36 hours. The peristalsis is the process which your muscles contracts and relaxes to help to push the chyme along the digestive and intestinal tubes. You can look at this entire system as a serial processing factory where one meal arrives and is processed at a time. Everything gets “piled” up in the colon sequentially. One can check his/her food transit time with the “beet juice” experiment. If you see the red beet color coming out within the 12 hours time then it is too fast (means little absorption); while if it takes 48 hours or longer then it is too slow. Toxification is the potential concern here along with  constipation. Finally, because matters are processed somewhat sequentially, one is ideally expected to have one bowel movement after every solid meal. If that is not the case, you may need ask yourself if you are “backed up” or not.

Well, that pretty much summarizes the overall system from a top-down food transit point of view. Now that you have a good idea on your food’s processing capabilities, in our next few blogs, we will dive into some of the key issues Americans are facing today in the digestive and intestinal area and highlight some important nutrients we can use to prevent and even possibly eliminate these concerns.


Posted by Paul


  1. {}

    This website should be reference for me because I just got a lot information from this. THIS IS THE BEST SITE FOR HOMEWORK!!!!!!!)!!!!!!!!!¡$!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Leave your comment

Please enter comment.
Please enter your name.
Please enter your email address.
Please enter a valid email address.