Introduction to the Digestive System

by Michael B. Schachter M.D., F.A.C.A.M.

The digestive or gastrointestinal intestinal system, which is also known as the gut, is important for many reasons. Problems with it may result not only in one of the many digestive system disorders, but also to illnesses in any system of the body, such as the nervous system or the immune system. The reasons for this will become apparent as we explore the digestive system.

Most of you have heard the expression "you are what you eat." Although there is a good deal of truth to this concept, a more accurate statement would be: "you are what you eat, digest, assimilate and incorporate." Although this statement is also obviously less than complete, it does incorporate the very important notion that a person’s health is based not only on the food he eats, but also on how well he is able to break down these foods and process them in such a way that they are useful to the body. This is not only a function of what one eats, but also other factors, such as a genetic predisposition, exposures to toxic substances and exposures to infectious agents.

The digestive system consists of the mouth and teeth at one end and the anus at the other. In between is a long tube like structure with different names and different functions. The esophagus is a tube that passes through the chest and connects the mouth to the stomach. The stomach leads to the small intestine or small bowel, which is a narrow long tube from which most of the food absorption into the bloodstream takes place. The small intestine leads into the large intestine, which is also known as the colon or the large bowel. In the large intestine, fluid is reabsorbed back into the bloodstream and feces or stool is formed. This waste product passes through the end of the large intestine called the rectum through the opening known as the anus. The large intestine or colon also houses more bacteria than all of the cells of the human body. These bacteria have the potential to be either harmful or beneficial to the body, depending on many factors that will be discussed in subsequent medical updates.

The digestive system then is basically a tube running through the body that interfaces the body with the outside World. Its two major functions are first, to allow useful and necessary substances into the body to promote growth and health, and second, to keep harmful substances out of the body.

Normal Digestive Functioning and What Can Go Wrong
Let’s start with the mouth. The process of digestion begins in the mouth with the mechanical breaking down of food by chewing and the release of saliva from the salivary glands, whose ducts enter the mouth. The importance of chewing is generally ignored by conventional and complementary physicians alike and is merely taken for granted. However, proper digestion requires extensive chewing, so that food is broken down to a liquid form before it is swallowed. Failure to do this is the reason for finding large undigested food particles in stool. Saliva contains enzymes that help to break down complex carbohydrates into simple sugars. Sufficient chewing time is necessary for this initial digestive process to occur.

At the turn of the century, considerable attention was drawn to this issue by a man named Fletcher, who advocated at least 100 chews before swallowing. He claimed that extensive chewing was absolutely necessary for good health and the term "Fletcherism" was applied to this practice. Although his position may have been a bit extreme, insufficient attention is paid to chewing well before swallowing today. Therefore, my advice to all of you is to chew your foods well, as this will lead to healthier teeth and gums and better digestion.

The process of digestion continues in the stomach after the food bolus passes into it from the mouth through the esophagus. The stomach secretes hydrochloric acid, mucus to protect the stomach walls from the acid, and proteolytic enzymes to begin the process of protein breakdown into smaller peptide molecules. These enzymes require an acid environment with the pH level being in the range of one or two, which is quite acid. The acid environment of the stomach also helps to kill bacteria, viruses, fungi and other microorganisms that enter the stomach with food. When stomach acid secretion is impaired, the stage is set for an increased risk of infection from organisms such as Candida or yeast and Helicobacter pylori, a bacterium that is associated with chronic gastritis, peptic ulcers and stomach cancer. Furthermore, low acid or hypochlorhydria will result in poor protein breakdown, and subsequent poor absorption of amino acids, the building blocks for many important chemical compounds and structures within the body.

Diagnosis and Treatment of Hypochlorhydria or Low Stomach Acid
How can one tell if he has low stomach acid? Surprisingly, one may have symptoms that are often associated with elevated stomach acid. One may experience burning pain and regurgitation discomfort in the upper abdomen and lower chest area. Additionally, one may feel gas in this area and burp excessively. After meals, one may feel that the food seems to remain in the stomach and has difficulty progressing through the intestines.

To diagnose a suspected low acid condition in the stomach, a complementary physician may order a gastric acidity test called a Heidelberg capsule. This capsule is the size of a large vitamin B or antibiotic capsule. It contains both a pH meter, which measures acidity in its environment, and a radio transmitter. The patient has a belt containing a radio receiver strapped around his abdomen. Signals from this radio receiver can be recorded on a strip of paper. The information recorded is the pH of the environment surrounding the Heidelberg capsule. The patient is asked to swallow the capsule and the recording of the pH begins immediately.

The method of administering this test that we do in our office is to attach a string to a loop on the capsule. Once the capsule is swallowed and enters the stomach, the pH should normally be in the acid range. If the pH remains neutral at around seven, then one may conclude that the patient suffers from achlorhydria or no stomach acid. At this point, the capsule may be gently removed from the stomach by pulling on the string so that the capsule passes through the mouth. If, on the other hand, the pH does drop to an acid pH of one, the patient may be challenged by having him drink a small quantity of bicarbonate of soda solution. This is an alkaline solution, which will bring the pH back up to eight or so. Stomach acid should then be secreted to acidify this solution within 10 to 15 minutes. The bicarbonate solution may be given four times, each time after the solution has been reacidified. A normal result occurs when reacidification takes place each time. If this doesn’t occur, then the diagnosis of hypochlorhydria may be made. Treatment of hypochlorhydria involves the administration of betaine hydrochloride or glutamic acid as supplements along with meals.

Diagnosis of Intestinal Permeability
The small intestine has two major functions. The first is to allow necessary substances into the bloodstream in order for the body to use these raw materials to grow and function properly. Among these substances are sugars, amino acids, fats, vitamins, minerals and other food factors. Pancreatic juices passing into the small intestine and secretions from the small intestine promote the completion of digestion, so that these smaller molecules may be absorbed into the bloodstream. When there is a problem absorbing these substances into the bloodstream, the patient is said to have a malabsorption syndrome.

The second major function of the small intestine is a protective one. It prevents toxic substances and large molecules, such as large protein molecules, from getting into the bloodstream. These large molecules cannot be handled well by the body and frequently cause the immune system to produce antibodies against them. This then may result in a series of inflammatory reactions that characterize food allergy reactions. They may also stimulate the body to produce antibodies against its own tissues, resulting in autoimmune disease as seen in some forms of arthritis and inflammatory bowel disease. When large molecules break through the intestinal barrier to enter the bloodstream, the patient is said to have increased intestinal permeability or a leaky gut.

The leaky gut itself may be caused by food allergy reactions, resulting in a vicious cycle, or by infections or toxic agents. Once a leaky gut is identified, it is important to correct the underlying cause or causes and also to attempt to repair the damage to the intestine, so that the leaky gut is corrected.

Recently, a simple test has become available commercially to test for a leaky gut. The patient is given a kit in order to do the test at home. The patient drinks a solution containing a known quantity of two sugars, namely mannitol and lactulose. Normally, the body is able to absorb mannitol, but not lactulose. Urine is collected for six hours and sent to a laboratory, where the mannitol and lactulose concentrations and total amounts are measured. Normal ranges have been established. If excessive amounts of lactulose are present, then a leaky gut is likely. If, on the other hand, insufficient amounts of mannitol are present, then malabsorption is present. Either way, treatment measures may be introduced.

Causes of Intestinal Permeability (Leaky Gut or Malabsorption)
Damage to the lining of the intestinal wall may bring about either poor absorption of necessary nutrients or the absorption of large or toxic molecules that may cause damage to the system, resulting in the so-called leaky gut. This damage may be caused by infectious agents, toxic substances, food allergies or intolerances, deficiencies of pancreatic enzymes or autoimmune processes, in which the body makes antibodies against its own tissues.

One of the first steps to take in trying to understand the cause of a damaged intestinal lining is to do tests that may help to determine if an infectious agent may be contributing to the problem. The kinds of microorganisms that may do this include bacteria, fungi or yeast and parasites. Some of the bacteria that may be pathogenic are pylori, which primarily damages the lining of the stomach, leading to peptic ulcers, E. Coli, Klebsiella, anaerobic bacteria and many others. A comprehensive digestive stool analysis and culture may be useful to determine if there is an abnormal growth of one or more of these bacteria. Conventional physicians often do endoscopies and take biopsies of the stomach to see if pylori is present. However, a simple antibody blood test to Helicobacter pylori can also be useful.

Antibodies against Candida Albicans and/or a growth of this organism may help to establish that there is a Candida overgrowth. Predisposing factors to the development of an overgrowth of Candida include exposure to antibiotics, use of birth control pills, use of steroid medications and a high sugar diet. This organism may cause a variety of symptoms, such as bloating and gas, vaginitis and depressive symptoms.

Parasite infections are much more common than one would think and conventional physicians often don’t think of the possibility and don’t order tests to check for them. Common parasitic infections include Amoeba Histolytic and Giardia lamblia. These can often be seen under a microscope when the stool is examined. If the stool is produced by a Purge, the likelihood of seeing the parasites is increased. Another excellent method of diagnosing parasites is to use a cotton swab in the rectum, as the parasites often hide in the lining of the intestine or rectum, rather than coming out in the stool.

Once the diagnosis of one or more of these infectious agents are made, the patient should be treated with herbs or medications for the affliction before taking the steps to repair the intestinal lining.

Other Causes of Impaired Intestinal Permeability
Any irritation to the gut lining can contribute to an increased permeability or a malabsorption of nutrients. Aside from infections, irritation may result from: (1) food allergies, (2) exposure to certain drugs, such as non-steroidal anti-inflammatory medications, some examples of which are ibuprofen, which is also known as Motrin or Advil, Naprosyn, or cancer drugs, (3) alcohol, (4) autoimmune disorders, (5) pancreatic or intestinal enzyme deficiencies, and (6) prolonged fasting.

Once a leaky gut or poor absorption is determined by the intestinal permeability test, one may be able to determine the cause by carrying out certain procedures or tests. To see if the problem is due to one or more medications, the possible offending agents may be eliminated for three weeks and the intestinal permeability test repeated. If there is improvement, then one would assume that the drugs had contributed to the abnormal test.

To determine if hypochlorhydria is contributing to abnormal intestinal permeability, a Heidelberg capsule test, as described in a previous Update, may be done. To see if lactose intolerance due to a deficiency of the intestinal enzyme lactase is a factor, a lactose tolerance test may be done. This test may be performed by having the patient drink a given amount of lactose solution. Over the next few hours, he breathes into a specially prepared tube, which is sent to the laboratory. There the amount of hydrogen gas and methane gas present in the tube is measured. If lactose is not broken down by the enzyme lactase in the intestine, the lactose is available for certain types of bacteria in the large intestine to produce the gases hydrogen and methane. These gases enter the bloodstream, circulate to the lungs and are given off by the lungs. If the amount of hydrogen and/or methane in the expired air is elevated, this indicates a lactase deficiency. Similar testing may be used to determine the presence of an overgrowth of bacteria in the small intestine or other types of enzyme deficiencies, simply by varying the substances ingested prior to the collection of expired air samples.

Treatment of the enzyme deficiencies would involve replacement of the enzymes orally or the avoidance of substances that cannot be broken down by the body, such as the elimination of dairy products if lactase deficiency is present. A small bowel overgrowth of bacteria may be treated by medications or herbs. To determine if food allergies are contributing to the abnormal intestinal permeability, certain blood tests or skin tests may be done.

The Liver and its Role in Detoxification of the Body
Once food is broken down in the stomach and small intestine, it is absorbed into the bloodstream, which travels first to the liver, where substances may be chemically changed. One of the main functions of the liver is to help the body modify toxic substances, so that they may be removed easily from the body through the urine via the kidneys or through the bowel via the feces. A failure of the liver to carry out this function properly will result in an accumulation of toxic substances that may be stored in the nervous system and in fatty tissues. This toxic accumulation may contribute to a wide variety of diseases and complaints.

For example impaired liver function may contribute to Alzheimer’s or Parkinson’s Disease, autoimmune diseases, Chronic Fatigue Syndrome, food allergies, chemical sensitivities, headaches, hepatitis, premenstrual syndromes, the development and outcome of cancer, and many other conditions. Basically, when the liver detoxification mechanisms are not functioning properly, the body is poisoned with a buildup of toxins. The toxins may originate from outside the body in the form of pesticides, alcohol, drugs, paint fumes, exhaust fumes and many others or from inside the body from the gut or from metabolic products.

So, in evaluating any patient one of the first steps we take is to evaluate the functioning of the stomach, intestines and other aspects of the gastrointestinal system and then treat any abnormality. A second step is to evaluate liver functioning, because a problem with this organ may contribute to so many disorders. It is important to realize that when a physician orders blood tests that are called liver function tests or a liver profile, which includes the measurement of SGOT, SGPT, bilirubin and alkaline phosphatase, he is not really measuring how well the liver is able to carry out its detoxification function. Rather he is generally measuring damage to liver cells, which result in an elevation in one or more of these enzymes. All of these tests may be quite normal, but the liver may still not be carrying out this function properly. To measure how well the liver is functioning requires a different kind of test.

How the Liver Carries Out its Detoxifying Functions
The liver helps in the removal of toxic and metabolic waste products from the body by converting them to a form which is soluble in water, so that they are easily eliminated in the urine formed by the kidneys. Other substances transformed by the liver are dissolved in the bile formed in the liver and eliminated in the feces after the bile passes into the intestines through the bile duct.

This detoxification process occurs in two phases, termed Phase I and Phase II. Phase I involves a system of enzymes known as the cytochrome P-450 mixed-function oxidase enzymes system. These enzymes react with toxins, drugs, alcohol, paint fumes and many other substances to form compounds that are capable of being transformed to water soluble substances by Phase II reactions. The previously mentioned substances may up regulate the cytochrome P-450 mixed oxidase system by inducing enzyme changes. Some of the products formed from Phase I reactions are actually more toxic than the original substances and can be harmful and even cancer producing if Phase II reactions do not take place properly. Also, during Phase I reactions, which often involve the oxidation process, free radicals may be formed, causing damage, unless sufficient amounts of antioxidants, such as Vitamins A, C, E and glutathione are present to neutralize them. With underlying liver disease, insufficient nutrients necessary for Phase I, damage from drugs, alcohol, birth control pills, amphetamines or Tagamet, Phase I is slowed down and this is called a slow detoxifier situation.

Phase II reactions involve a chemical reaction called conjugation, in which fat-soluble substances formed in Phase I or present independent of Phase I are combined with certain substances to form water-soluble compounds. To carry out these conjugating reactions, the liver uses glutathione, sulfate, glycine, acetate, cysteine and glucuronic acid molecules. If some of these substances are lacking, then phase II reactions may be impaired, resulting in what is called a pathological detoxifier situation.

The important thing here is that with relatively simple tests, one can determine how well each phase of liver detoxification is working. Then appropriate therapeutic measures may be taken to correct the problem, improve liver detoxification and thus improve the health of the patient.

Tests to Assess Liver Detoxification and Some Therapeutic Measures
The Functional Liver Detoxification Profile uses two common challenge substances to evaluate liver detoxifying ability. Caffeine, which is acted on by P-450 enzymes, is used to assess Phase I. Sodium benzoate, a common food additive, is used to assess Phase II, since it is conjugated with glycine to produce hippuric acid. The patient can carry out the testing procedure at home with the help of a testing kit. Samples collected by the patient are sent to a certain laboratory for measurements of caffeine and hippuric acid. The test results and interpretation are sent to the ordering physician. The patient drinks a known amount of caffeine and benzoic acid solution. Subsequently, during the next few hours, the patient collects a saliva specimen to measure the caffeine and a urine specimen to measure the hippuric acid.

If the caffeine is relatively high, this indicates an overactive phase I due to enzyme induction, probably due to exposure to internal or external toxins. This also suggests potential increase free radical production due to excessive P-450 activity. A low caffeine clearance indicates slow dysfunctional P-450 enzyme activity. This suggests metabolic difficulty in removing toxic chemicals from the system. So, the caffeine clearance helps us to understand the status of Phase I liver detoxification.

A slow conversion of benzoate to hippurate after the sodium benzoate challenge is indicative of inadequate Phase II detoxifying reactions. A high hippurate level in the urine has no pathological significance and probably indicates that phase II detoxification is adequate. An elevated caffeine clearance to benzoate conversion ratio indicates increased liver cytochrome P-450 activity relative to phase II conjugation with glycine. These individuals have been termed "pathological detoxifiers." A reduced caffeine clearance to benzoate conversion ratio indicates decreased liver cytochrome p-450 activity relative to the glycine conjugation. These individuals have been termed "slow detoxifiers."

The treatment of these imbalances are different. For example, when Phase I is increased, attempts should be made to reduce the drug, chemical or toxic load and antioxidants, such as Vitamins A, C, E, beta carotene flavonoids, pycnogenol and selenium should be supplemented. When the Phase I system is decreased, a nutritional detox program is usually recommended with biochemical liver support such as milk thistle herbs and lipotropic nutrients like choline, inositol and methionine. When Phase II conversion is slow, liver support is also helpful, along with conjugating nutrients, which are likely in short supply. These include glycine, glutathione, N-acetyl cysteine, glucuronic acid, taurine and others. It is important to understand the status of the liver detoxification system because if for example you use the treatment to upregulate Phase I when Phase II is inadequate, then the patient may get worse. With proper understanding, an intelligent treatment program may be planned.