The Digestion Process

In Psalm 139:14, King David, under inspiration of the Holy Spirit, declared: “I will praise Thee; for I am fearfully and wonderfully made.” More and more we are led to echo these words of David as we study the structure and function of the human organism and see therein reflected the marvels of divine engineering. It is God’s wish that we should understand the working mechanisms within the human body so that we can develop an intelligent life style that works in harmony with the laws of our being. This will, in turn, enable us to keep our body temples pure and undefiled as a “living sacrifice, holy, acceptable unto God.” Romans 12:1.

Those who strive, by the grace of God, to be faithful stewards of their physical being will also reap the rich reward of an increased spiritual dynamic in their lives that will help facilitate the development of a righteous character. For these reasons, we must concur with God’s prophet in declaring that “the health should be as faithfully guarded as the character.” Education, 195.

The digestive system is one of the major systems that God has established within the human body, and we need to become conversant with its structure and function. Too often this vital component of the body is abused, resulting in dysfunctional problems and ill health, which, in turn, affect the mind and dull the spiritual perceptions. A proper state of things is therefore vital as this relates to our quest for the eternal crown.

The digestive system begins at the lips where food first crosses the threshold into the system and terminates at the anus where waste residues are finally expelled from the body. What happens in between is truly a miracle of God’s ingenuity.

As food is being chewed, it becomes more liquefied by the saliva, making it more easy to swallow. Also, a certain enzyme called ptyalin, present in saliva, begins the chemical breakdown of cooked carbohydrates (CHO) and sugar into maltose, which is a simpler form of sugar. After food has been adequately chewed and then swallowed, it is passed downwards to the stomach via the esophagus, a muscular tube about 9–10 inches long. Food does not simply drop down into the stomach in the same way as one can drop a pebble down a well. The esophagus conveys the food downward through the action of peristalsis. This conveyance mechanism takes place when the circular muscle fibers in the esophagus relax in front of the swallowed food while also contracting behind it, thus moving the material downward toward the stomach. While the act of swallowing food is done voluntarily, the remaining part of the journey comes under the control of the autonomic (involuntary) nervous system.

The esophagus connects with the upper part of the stomach. However, before food can finally empty into the stomach, it has to pass through a special entryway called the cardiac sphincter. This portal, which is normally kept in a tightly closed position, becomes relaxed and opens as the peristaltic wave rolls down the esophagus and impinges upon this initial upper area of the stomach; thus allowing food to pass within.

The stomach may not share the same glamorous image as the heart or the brain, yet it is as worthy of recognition as any other organ of the body. After receiving food from the esophagus, the stomach acts as temporary storage while its muscular contractions mix the food with its gastric juice. Peristaltic waves in the stomach slowly ripple down the length of its muscular walls at about three times per minute in order to produce this necessary mixing and help to liquefy the ingested food stuffs.

Various glands in the mucus lining of the stomach collectively produce a clear, colorless mixture called gastric juice. Some of these glands generate a substance called hydrochloric acid (HCl). This serves to acidify the food and acts as an antiseptic and disinfectant, rendering harmless many organisms ingested with the food. There are other glands within the stomach wall, which produce a substance called pepsinogen. When pepsinogen is released and interacts with HCl, it is converted to pepsin, a powerful enzyme that begins the breakdown of protein foods into more soluble substances known as peptones. Rennin is another product secreted by the stomach and is involved in the digestion of casein, a milk protein. Also present in small amounts is a fat splitting enzyme called gastric lipase.

Especially interesting is the fact that some cells specialize in producing a heavy layer of mucus that coats the lining of the stomach. This is crucial to the stomach’s own defenses; and if this barrier did not exist, preventing the HCl and pepsin from having direct contact with its delicate lining, the stomach would start to digest itself. Unfortunately, this can happen (though on a limited scale) in the case of a gastric ulcer where the defenses are breached and the gastric juice makes direct contact with the stomach lining. This condition produces much discomfort and, if not rectified, can result in the ulcer eroding its way completely through the stomach wall. Ulceration is even more common a little lower down from the stomach in the duodenum.

There are many causes for peptic ulceration, though the major factors are:

  • Irregular meal times
  • Tension, anxiety, and emotional stress
  • Ingestion of irritants to the stomach lining, e.g., hot spicy foods, alcohol
  • Smoking

Diagnosis of peptic ulcer, either gastric or duodenal, can only be made for sure after careful medical investigation (usually involving an inside view of the stomach through a fiber-optic instrument.) Prevention, of course, is always better than cure; and correcting faulty life style practices that lie at the root of this condition is obviously the wisest course both for the prevention and cure of peptic ulcer.

One final ingredient of gastric juice that is worthy of mention is a substance known as the intrinsic factor. This vital component is necessary for the absorption of vitamin B-12. If the stomach does not produce sufficient amounts of the intrinsic factor, it will result in B-12 deficiency in the system. This special vitamin is, in turn, necessary for the production of healthy red blood cells. Insufficient levels produce a blood disorder called pernicious anemia. Vitamin B-12 deficiency can also cause chronic degeneration of the spinal cord, resulting in various degrees of nerve dysfunction to other parts of the body. People who have had surgical removal of some or all of the stomach are obviously prime candidates for B-12 deficiency due to their reduced or non-capacity to produce sufficient amounts of the intrinsic factor. Fortunately, whatever might be the causes of B-12 deficiency as described here, the problem can be easily corrected by periodic injections.

The stomach secretes between one to two liters of gastric juice per 24-hour period. There are two basic ways by which this happens: the first and immediate way is through stimulation of the vagus nerve, a major nerve extending from the brain which gives off branches to the stomach, which in turn initiate the secretion of gastric juice. The thought, sight, and smell of food is sufficient (when a person is hungry) to trigger this mechanism. A further aspect of nervous stimulation is produced when food enters the mouth and “tickles” the taste buds. This also results in increased vagal activity. Further still, food that enters the stomach, causing initial distention, will also serve to further increase production of gastric juice. The second phase of gastric secretion (the humoral phase) is initiated later in the digestive process as a result of protein breakdown. This causes the release of gastrin, a hormone that stimulates the stomach via the blood stream.

Regular meal times, as already mentioned, are essential in order to keep the stomach healthy and able to function to the optimum. If regularity is maintained, the body’s biological clock will prime the digestive tract and make it ready for action at specific times of the day in anticipation of food. God wants us to understand the importance of regularity; and for this reason, He has counseled us to maintain this factor in our eating habits. You may have noticed that if circumstances prevent you from taking a meal at the usual time, the appetite begins to wane until we start feeling “past it.” We may still retain an inclination to eat, but the hearty, wholesome relish is gone. At such times, if the physical work demands placed upon us will permit, it would be better for the system if we were to forego eating a late meal well outside of our usual routine and wait until the next established meal period comes around.

Other factors included with regularity that help us take proper care of the digestive system are as follows:

  • Chew the food well
  • Allow at least five hours between each meal
  • No smoking
  • No drinking at meals

After food has been well mixed and liquefied in the stomach (it is now referred to as chyme), small amounts are allowed to pass through the stomach’s lower exit into the small intestine. The first nine to ten inch section of the small bowel is called the duodenum. It is here that digestion takes its next major step. Enzymes from the pancreas are secreted into the duodenum to continue the breakdown of proteins, fats, and carbohydrates into smaller components. Bile from the gallbladder is also secreted into the duodenum. The function of bile is to emulsify fats so that they can be more easily dealt with by lipase, the fat digestion enzyme from the pancreas. The acidic chyme is also neutralized in the duodenum by bile and pancreatic enzymes which are alkaline in nature. The gallbladder and pancreas, under the influence of nervous and humoral stimulation, are also led to release their digestive juices.

As the liquid chyme continues further down into the small intestine, it comes under the action of other digestive enzymes which are released from the wall of the gut. These enzymes finalize the breakdown of protein foods into amino acids, carbohydrates into simple sugars, and fats into glycerol and fatty acids.

After the breakdown of ingested foodstuffs, the next step in digestion involves the absorption of this material from the bowel so that it can be utilized by the body. This is accomplished through the action of countless minute structures called villi.

The villi are tiny, finger-like projections that line the wall of the small bowel for the major part of its length. The villi are so constructed that collectively they present a much larger surface area for the absorption of nutrients than could be realized if the lumen of the bowel were smooth and even. Digested materials absorbed by the villi are then shipped off to the liver, via the bloodstream, for processing. Some of the digested fat substances and fat-soluble vitamins are released directly into the general circulation via a more circuitous route, rather than going to the liver first.If digested protein substances, for example, were released directly into the circulation without being processed first by the liver, a very toxic condition could develop in the body. It is for this reason that people with cirrhosis, who have a diminished liver function, must be careful with their diet, especially regarding protein intake. If a poorly functioning liver is overwhelmed by an over ingestion of protein, which it does not have the capacity to fully handle, it has little choice than to allow unprocessed material to pass out into the blood stream. In extreme cases, this could result in coma and even death.

The liver is also a marvel of God’s design and it fulfills many functions, one being, serving as a factory, or initial service center, for digested materials. Many substances undergo further changes here before being released into the general circulation for use by the body.

Another major function of the liver is to take glucose (the end product of CHO breakdown) and convert it into a more concentrated form called glycogen. This material is then stored temporarily inside the liver cells and later reconverted into glucose when needed by the body. By means of this function, the liver is involved in maintaining the correct level of glucose in the bloodstream. Much could be said about this very versatile organ, but space will only permit this very brief mention.

By the time ingested material reaches the large intestine, it is still liquid and almost, if not completely, void of all nutritive elements. The peristaltic action of the colon is much slower than in the small bowel, and water is absorbed from digestive residues as they are gradually conveyed along inside the colon. This process results in solidifying the waste material and formation of the feces.

Peristalsis often increases in the colon for a time immediately after a meal, causing waste to be more rapidly moved onward on its final journey through the system. When waste material is emptied into the rectum, nerve pathways in the bowel, in contact with the spinal cord, initiate the desire to go to the bathroom and expel the waste material. Nerve pathways leading from the spinal cord also ascend upward to the brain, thus alerting the individual to natures call.

Colon cancer is a major cause of disease in America today. Probably the greatest causative factor is unhealthy life style, especially faulty diet. The highly refined diet that so many seek to exist on today is grossly deficient in fiber and certain protective foods. Low fiber intake results in a slow passage of food waste through the system (especially in the colon). This is referred to as the transit time. This slow movement of refuse through the system allows cancer initiating substances to remain in contact with the bowel wall for an extended period of time, thus providing the ideal conditions for disease to establish itself.

For example, a well-known breakfast cereal manufacturer, in a promotional for its high fiber products, stated that the standard, low-fiber, white bread, cheese sandwich can take a week to pass through the digestive tract! Little wonder that constipation is so common in the so-called civilized world when so many live on such an uncivilized diet. Of course, the point the breakfast food producer was obviously trying to make was that their high fiber cereal did not behave in such a sluggish fashion as the average cheese sandwich and contribute to a clogged up system.

Fiber is important to the health of the system, especially the colon. Medical science has amply documented the fact that people who eat an unrefined diet, naturally high in fiber, have a much shorter transit time and a much lower incidence of colon cancer. Vegetarians automatically receive an adequate intake of fiber apart from the other benefits that such a diet provides; and, as far as the colon is concerned, they also have far less incidence of constipation, diverticulosis, and appendicitis.

To be kept health and functioning well, the divinely prescribed diet of fruits, grains, nuts, and vegetables, coupled with the other healthy life style factors of water, exercise, rest, abstemiousness (see Ministry of Healing, 127), will keep his and the rest of the system healthy and sound.

It may be well to remind ourselves that as human beings, we can easily go to extremes in our philosophy and practice of life style. A tendency has developed among some people to view the colon as the key organ of the body in respect to physical well being. Much of the diseases that afflict modern man are believed to originate in the colon and consequently can be prevented and also cured by placing special emphasis upon treating this organ. While there may be genuine medical grounds for a person from time to time to resort to an enema, or the occasional colonic, it is neither a healthy practice nor a sign of balanced thinking to make this the chief focus and practice on a regular basis.

The inspired counsels on health given us by God present a much broader, well-balanced philosophy on the question of health and the cause and treatment of disease. In fact, Ellen White was led to give timely caution to those in her day who had a fixation on the colon: “There are men who make a specialty of treating the rectum, and some feel that they have been greatly benefited. But I have been instructed that this treatment, as well as many surgical operations, leaves with many a serious weakness.” Paulson Collection, 217.

We have much to be thankful for. Especially we need to thank God for the marvelous gift of life and the wonderful bodies wherein we are able to live out this precious gift. Therefore, as we eat, let us eat to His glory, eating only those things that will do us good, and also with thankful hearts rejoice that we have amazing living organisms that, under God’s continued and immediate agency, are able to assimilate the nutritious bounties of the earth, perpetuating in turn the glorious gift of life!