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This section contains one of the most important concepts relating to the use of supplemental digestive enzymes. The main use of supplemental digestive enzymes is to aid digestion. This will provide a brief description of the digestive system, and more importantly some of the factors that create the need for an adequate digestion. As cooking and processing habits induce intermolecular and intramolecular changes within the food, and aging and other factors contribute to insufficient secretion, it is important to review the main digestive process and recognize the conditions that impede its normal function which result in the need for supplementation.
Digestion is the physiological process of rendering the food we eat useable by and beneficial to our cells. It depends heavily on biological macromolecules that are called digestive enzymes, and their optimum reaction conditions. A malabsorption or poorly digested food will have negative effects on the metabolism because essential nutrients will be missing, and normal cell function will be impaired.
In biological systems, only hydrolytic enzymes can breakdown (in a way that is compatible with life) the macromolecules such as carbohydrates (starch, glycogen), proteins, and lipids, into smaller molecules that can be absorbed into the cells, and integrated into various biochemical reactions. Thus, by breaking down the macromolecules, digestive enzymes make nutrients available to the cells.
Digestive enzymes, as a specific group, breakdown carbohydrates to simple sugars, proteins to amino acids, and triglycerides to fatty acids and glycerol. The mechanical process of disintegration such as mastication, mixing, churning, and grinding facilitates the action of the enzymes. The hydrolysis of the food macromolecules enables them to be taken up by the intestinal cells and then be released into the blood system. Digestive enzymes contribute also to the delivery of vitamins and minerals by the hydrolysis of the macro structures of the food to free the vitamins and minerals. Other enzymes and transport proteins are involved in binding and carrying the coenzymes or co-factors, i.e., some vitamins and minerals throughout the blood and into the cells. Without this function of hydrolysis by the digestive enzymes, nutrients will remain trapped into the macro structures of the food.
The process of breaking down the food to benefit the body is accomplished by a complex system of nerves, hormones, and enzymes. The nerves and hormones signal to the body what enzymes are needed and when they are needed to do the work: the enzymes are the molecules that will perform the biochemical task of breaking down the food we eat. The action of the enzymes in the digestion process starts in the mouth, while their secretion starts at the thought and/or sight of the food. For instance, at the sight, smell, or thought of a particular food, one may start salivating. This saliva, in addition to lubricating the food, contains the enzyme amylase (ptyalin) to help break down the starchy foods in the diet. Thus, there is a psychoneuro-humoral coupling to the enzyme secretion, regulation and activity. This tight regulation is carried on throughout the digestive system.
The Digestive System and Digestive Enzymes
As stated above, digestion is a vital function to sustain life. The digestive process is supported anatomically by a whole system of organs and biochemically by several hormones and enzymes. The digestive system is first comprised of the mouth (teeth, tongue, salivary glands) and the esophagus to carry the food from the mouth to the internal organs starting with the stomach. The stomach is a pouch like structure which function is to store, churn, mix with gastric secretions, predigest proteins, and move the food in a very controlled and rhythmic manner into the small intestine. Some limited absorption may take place in the stomach wall.
The next portion of the digestive tract, after the stomach, is the small intestine: a long tube about 12 ft long with a smaller diameter compared to the large intestine. It is the main site of digestion and absorption where most digestive enzymes are brought together to chemically breakdown the food and allow the uptake of the nutrients into the blood stream. The small intestine is divided into three regions with specific cellular and physiological functions: the duodenum, the jejunum, and the ileum.
The duodenum is a very short tube (10 inches) where most of the liver/gallbladder, and pancreatic secretions are mixed with the chyme coming from the stomach. The jejunum is about 3 ft. long and is the site of absorption of sugars (glucose and other monosaccharides), fatty acids, monoacylglycerols, glycerol, cholesterol, amino acids, peptides, vitamins, folate, electrolytes, iron, calcium, water. The ileum is about 7 ft. in length and is also a site of absorption of nutrients such as bile acids, vitamin B12, electrolytes, and water. It is rich in lymphatic tissue.
Overall, the small intestine provides a large surface area for enzymatic activity and for absorption of the nutrients. The surface area of the human small intestine is about 200 m2. The next digestive tract section is the large intestine. It is about 5 ft long and its main function is to absorb water and electrolytes, form, store and expel feces from the body.
In addition to the buccal cavity, the esophagus, the stomach, the small intestine, and the large intestine ending with the rectum, there are adjacent organs such as the liver, the pancreas, and the gallbladder which synthesize and secrete the various hormones and enzymes needed for proper digestion.
Biochemical Changes In Foods
All human foods are made up of biological molecules, although some synthetic additives are increasingly part of the dietary intakes. The biological molecules of the foods contain amino acids, fatty acids, various monosaccharides, and other monomers and functional groups. These various monomers are linked together by various types of covalent bonds. The most common linkages (covalent bonds) found in biopolymers are:
The types of bonds mentioned are the most commonly found in human foods. The human digestive system is equipped with enzymatic processes to hydrolyze these types of bonds to release the monomers needed by the cells for maintenance, growth, reproduction, defense and other vital functions. However, several man-made processes dealing with cooking and preservation may induce other kinds of chemical bonds in the food biomolecules. In many instances, the bonds formed by these processes are not amenable to natural enzymatic action by human digestive system. This lack of enzyme action on the bonds artificially produced by food processing reduces the nutritive value of the foods. Some of the processes that may induce bonds that are very difficult if not impossible to hydrolyze by human endogenous enzymes include high heat application (e.g., cooking) and irradiation.
The application of heat to food biomolecules (by conventional cooking or microwave) has several consequences including, breaking some chemical bonds in foods, but also creating other types of bonds. For instance, mild cooking of starchy foods helps breakdown the cellulosic material that very commonly encapsulates the starch granules. This mild treatment is good as it facilitates the action of amylases on the starch. Other beneficial consequences of mild cooking include enhancing digestibility, imparting flavor to foods, and destroying toxins and microorganisms.
However, extreme heat application to meat and other foods induces formation of chemical crosslinks among and between side chains of amino acids and other reactive groups (Knipfel et al., 1982; Pokorny et al., 1985; Baker et al., 1984). Some of these crosslinks are not susceptible to hydrolase activity as no known proteolytic enzyme in human digestive system can break them down. The amino acids more prone to be involved in crosslinking as result of high temperature cooking include for instance: lysine, cysteine, histidine, tyrosine, methionine. Some of these amino acids, when involved in crosslinks that are not hydrolyzed would not be available to the body for absorption, resulting in loss of amino acids. It should be noted that some of these amino acids are essential amino acids. In addition to the loss of amino acids, cooking of meat at high temperature for a relatively long time also destroys valuable vitamins, and promotes formation of free radicals in the lipids. Studies have indicated that the loss of nutritive value in meat is correlated to cooking time and temperature. Thus, the application of heat in food processing has to be done in a very balanced manner to obtain the various benefits without jeopardizing the nutritive value of the food.
Other food products prone to deleterious effects by heat application during cooking or other processes include dairy products (Wardell, 1984; Kilshaw, 1982), vegetables, and grains. In general, heat denatures and promotes crosslinks in proteins, thus inactivating enzymes and/or lowering digestibility of the proteins. In the case of starchy foods, excess heat not only denatures the endogenous amylase, but also decreases the digestibility of the starch. Asp et al., (1987) showed that heating reduces the digestibility of starch by making it less susceptible to amylase hydrolysis. Furthermore, heated starch has been shown to decrease the digestibility of accompanying fats and proteins in the diet (Livesey, et al., 1990). The main objective in cooking should be to apply optimum heat that will render the food wholesome and tasty but not reduce its nutritive value.
Proteins and other biopolymeric compounds may also react to heat by undergoing structural modification: unfolding of the molecule, and if more heat is added, there will be further reaction among reactive functional side groups and ultimately coagulation of the polymer. Both excess coagulation and oxidation may reduce digestibility of foods. Davies et al., have shown that as further oxidation takes place within proteins, their resistance to proteases increases.
Another preservation method that affects food biomolecules is irradiation. When used at high doses, irradiation can drastically affect the chemical structure of food molecules by breaking bonds and initiating a cascade of reactions that result in formation of cross links, inactivation of endogenous enzymes, destruction of vitamins, and formation of highly reactive free radicals.
Food additives: The use of additives in foods has been intensified as a result of methods of production, and distribution. The intentional food additives include:
Most of these additives will have some effect on the organism. Any additive that does not "benefit" the organism should be used with great caution (even if its toxicity to humans is not established) because it may require some form of metabolism by the liver which will involve energy and use of valuable nutrients.
Effects of Diet on Digestion
A "low stress diet" is one that minimizes digestive and systemic stress, and a "high stress diet" is one that causes either digestive or systemic stress (Andrews, 1998). A proper diet with adequate digestive system functioning will minimize gastrointestinal stress. Digestive enzymes are key part of the digestive process: their adequate secretion and optimal activity on the various food substrates will provide the body with overall metabolic support to maintain itself and resist diseases. However, when the lack of enzymes and consumption of "high stress diet" impair the digestive process, the body's conditions weaken, and it becomes more susceptible to metabolic disorders and infections. Many conditions such as high intake of excessively processed foods, aging (Holt, 1982; Schneider and Reed, 1985) and various environmental factors may create a burden on the digestive process. According to Andrews (1998), systemic stress may occur even with proper digestion and absorption if the nutrients needed by the body are simply not present in the body. He described a high stress diet as one with all or some of the following characteristics:
Results of eating a high stress diet may include any combination of the following:
The various studies reviewed by Gardner and Steffens (1995) indicate the bio-availability and bio-activity of orally ingested hydrolytic digestive enzymes. These studies and others have also demonstrated the physiological and biochemical importance of taking supplemental enzymes. The condition described above as "high stress diet" may well be remedied with supplemental enzymes that are active within the gastrointestinal environment, and a "low stress diet" may be maintained with additional oral enzymes. In fact, in cases of pancreatic insufficiency, steatorrhea and cystic fibrosis, supplemental digestive enzymes are prescribed to patients to assist them in the hydrolysis of food molecules (Sighu and Tandon, 1996; O'Keefe et al. 1996). This indicates the effectiveness in the use of the ingested exogenous digestive enzymes. In the present discussion, the purpose is to extend the intake of the supplemental digestive enzymes as preventative dietary supplements to help maintain homeostasis.
When cells are helped by:
they can mount an adequate defense against many health threatening conditions.
When cells are deprived of adequate nutrients by:
they are at their highest stress level, as they are lacking what they need to survive but they are also being supplied with potentially toxic compounds. Proper nutrition is the first line of defense, and digestive enzymes (endogenous and supplementary) are key tools to achieving such a state.
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