Stephen Barrie, ND
Proper digestion is a prerequisite for optimal health. Without adequate breakdown and assimilation, even the best dietary intake is of diminished benefit to the body. Additionally, incomplete breakdown may lead to the absorption of macromolecules (including whole bacteria), intestinal and systemic toxemia, and intestinalirritation, infection, and dysbiosis leading to food allergies (see Chapters II:Food Allergy Testing and IV:Food Allergy), toxemia (see Chapter IV:Bowel Toxemia), and many chronic degenerative and autoimmune diseases. The CSDA (Comprehensive Digestive Stool Analysis) is a battery of integrated tests that evaluate digestion and intestinal function, environment and absorption.
tion. Salivaryenzymes (lingual lipase, salivary amylase, and ptyalin) initiate fat and starch digestion.3 Stomach: The stomach mechanically churns food, breaks up and emulsifies fats, exposes molecules to additional enzymes and produces 1 to 2 liters of gastric juices, consisting of:4 1. Hydrochloric acid: secreted by the parietal cells, which denatures proteins, converts pepsinogens to active form pepsin, renderssome minerals (e.g., calcium) and iron more absorbable, and helps kill bacteria in ingested matter. The acid was previously thought to create a sterile environment; a recently discovered exception being the presence of Helicobacter pylori. 2. Mucus: forms an acid and pepsin resistant coating for the stomach. 3. Intrinsic factor: bonds with vitamin B12 and is necessary for intestinal absorption. 4.Rennin: clots milk. 5. Gastric lipase: has weak fat-splitting activity. 6. Miscellaneous enzymes: control gastric secretions. Small Intestine: Most digestion and absorption takes place in the small intestines through the action of enzymes secreted by the pancreas, Crypts of Lieberkuhn, and the liver.4 The primary enzymes and secretions include: 1. Pancreatic juices: (2.5 L/day) are secreted bythe pancreas under the control of the vagus nerve, and the duodenal hormone secretin. Its production in turn is stimulated by the presence of fat and acid chyme. 2. Bicarbonate: neutralizes stomach acid. 3. Trypsinogen and chymotrypsinogen: are activated to trypsin and chymotrypsin. These enzymes digest proteins by cleaving polypeptides to oligopeptides and small amounts of free amino acids. Mostdietary protein is absorbed in the upper jejunum. 4. Amylase: splits starch to maltose. 5. Maltase: splits maltose to glucose. 6. Lipase splits fats to monoglycerides and free fatty acids. 7. Bile: secreted by the liver (700 mL daily) is stored in the gall bladder. Bile salts emulsify fats to allow the action of water soluble lipases. The Crypts of Lieberkuhn of the intestinal mucosa also producesmall amounts of digestive enzymes and immunoglobulins. In addition, small amounts of microbial-derived enzymes are found in the small intestine. Large Intestine: The major role of the large intestine is to absorb approximately a liter of water daily and provide a controlled route for excretion of waste products and toxic substances. The large intestine also provides an environment for microbialfermentation and degradation of carbohydrates (CHO) that results in the production of short chain fatty acids
A TEXTBOOK OF NATURAL MEDICINE
The Gastrointestinal Tract
The major function of the gastrointestinal system is to break down and absorb nutrients. Energy liberated by the digestive process is used by the body for repair and growth.1 The absorption of nutritional energy is inseparablefrom the process of complete digestion because the energy in foods consists mostly of polymers (e.g., starch, triglycerides, and proteins), whereas the actual absorbable and usable fuels released transported from the intestine to the body tissues are monomers or specially reconstituted polymers (e.g., chylomicrons). The digestive tract has the paradoxical dual role of discriminately allowing...