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Carbohydrates - Fuel For The Human Body (view source)
Revision as of 18:16, 29 March 2021
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=== Classification Of Carbohydrates ===
=== Classification Of Carbohydrates ===
Carbohydrates, also known as saccharides, are classified according to the number of single carbohydrate molecules in each chemical structure. Carbohydrate compounds having just one carbohydrate molecule are called monosaccharides; compounds with two carbohydrate molecules are called disaccharides; and those compounds containing more than two carbohydrate molecules are named polysaccharides. All carbohydrates either are monosaccharides or can be hydrolyzed (broken down) into two or more monosaccharides.
Carbohydrates, also known as saccharides, are classified according to the number of single carbohydrate molecules in each chemical structure. Carbohydrate compounds having just one carbohydrate molecule are called monosaccharides; compounds with two carbohydrate molecules are called disaccharides; and those compounds containing more than two carbohydrate molecules are named polysaccharides. All carbohydrates either are monosaccharides or can be hydrolyzed (broken down) into two or more monosaccharides.
==== Glycogen ====
==== Glycogen ====
Glycogen is the reserve carbohydrate in humans. It is to animals as starch is to plants. Glycogen is very similar to amylopectin, having a high molecular weight and branched chain structures made up of thousands of glucose molecules. The main difference be- tween glycogen and amylopectin is that glycogen has more and shorter branches, result- ing in a more compact, bush-like molecule with greater solubility and lower viscosity (less stickiness or gumminess).
Glycogen is the reserve carbohydrate in humans. It is to animals as starch is to plants. Glycogen is very similar to amylopectin, having a high molecular weight and branched chain structures made up of thousands of glucose molecules. The main difference between glycogen and amylopectin is that glycogen has more and shorter branches, resulting in a more compact, bush-like molecule with greater solubility and lower viscosity (less stickiness or gumminess).
Glycogen is stored primarily in the liver and muscles of animals. About two-thirds of total body glycogen is stored in the muscles and about one-third is stored in the liver.
Glycogen is stored primarily in the liver and muscles of animals. About two-thirds of total body glycogen is stored in the muscles and about one-third is stored in the liver.
Like starch and glycogen, cellulose is composed of thousands of glucose molecules. It comprises over 50% of the carbon in vegetation and is the structural constituent of the cell walls of plants. Cellulose is, therefore, the most abundant naturally-occurring organic substance. It is characterized by its insolubility, its chemical inertness and its physical rigidity. This polysaccharide can be digested only by herbivores such as cows, sheep, horses, etc., as these animals have bacteria in their rumens (stomachs) whose enzyme systems break down cellulose molecules. Humans do not have the enzyme needed to digest cellulose, so it is passed through the digestive tract unchanged.
Like starch and glycogen, cellulose is composed of thousands of glucose molecules. It comprises over 50% of the carbon in vegetation and is the structural constituent of the cell walls of plants. Cellulose is, therefore, the most abundant naturally-occurring organic substance. It is characterized by its insolubility, its chemical inertness and its physical rigidity. This polysaccharide can be digested only by herbivores such as cows, sheep, horses, etc., as these animals have bacteria in their rumens (stomachs) whose enzyme systems break down cellulose molecules. Humans do not have the enzyme needed to digest cellulose, so it is passed through the digestive tract unchanged.
=== The Role Of Carbohydrates In The Body ===
Five subheadings follow in this lesson subdivision, but there is actually only one ba- sic role of carbohydrates in the human diet: to supply energy. It should always be kept in mind that carbohydrates or calories alone cannot adequately supply our energy needs, for we must have our carbohydrates in combination with other needs, such as proteins, water, vitamins, minerals, fats, etc. This means that a diet of refined sugar, refined rice, flour products and other “food fragments,” though it supplies calories, cannot satisfac- torily comprise the bulk of anyone’s diet. A person on such a diet would suffer many problems, for the organism is not capable of living long or well on bare carbohydrates alone. They must be obtained in combination with the other essential food factors to be truly useful in the overall energy production and nutrition of the organism.
Five subheadings follow in this lesson subdivision, but there is actually only one ba- sic role of carbohydrates in the human diet: to supply energy. It should always be kept in mind that carbohydrates or calories alone cannot adequately supply our energy needs, for we must have our carbohydrates in combination with other needs, such as proteins, water, vitamins, minerals, fats, etc. This means that a diet of refined sugar, refined rice, flour products and other “food fragments,” though it supplies calories, cannot satisfac- torily comprise the bulk of anyone’s diet. A person on such a diet would suffer many problems, for the organism is not capable of living long or well on bare carbohydrates alone. They must be obtained in combination with the other essential food factors to be truly useful in the overall energy production and nutrition of the organism.
==== Carbohydrates Supply Energy ====
The body uses carbohydrates directly from the monosaccharide glucose. Glucose is in the blood and extracellular fluids (lymph) and can be made from glycogen. Glycogen is stored in the liver and muscles and in smaller amounts in the other organs and tissues of the body. Energy is derived from glucose by the splitting of the glucose molecules into smaller compounds and oxidizing these to form water, which frees quite a large amount of energy.
The body uses carbohydrates directly from the monosaccharide glucose. Glucose is in the blood and extracellular fluids (lymph) and can be made from glycogen. Glycogen is stored in the liver and muscles and in smaller amounts in the other organs and tissues of the body. Energy is derived from glucose by the splitting of the glucose molecules into smaller compounds and oxidizing these to form water, which frees quite a large amount of energy.
Practically the entire fat store of the body can be used up without detriment to health. Because of this fact, and the fact that the body can also create carbohydrates from amino acids, fasting is a very safe practice from the standpoint of maintenance of normal blood sugar levels, of normal neurological functioning and of meeting all the body’s various energy needs.
Practically the entire fat store of the body can be used up without detriment to health. Because of this fact, and the fact that the body can also create carbohydrates from amino acids, fasting is a very safe practice from the standpoint of maintenance of normal blood sugar levels, of normal neurological functioning and of meeting all the body’s various energy needs.
==== Carbohydrates Provide Fuel for the Central Nervous System ====
Nerve cells are very dependent upon glucose for their functioning. According to physiology texts, the glycogen in nervous tissues remains constant and is not mobilized for conversion to glucose. When insufficient carbohydrates are consumed to meet the energy needs of the central nervous system, besides the occurrence of gluconeogenesis, another phenomenon occurs during a fast of three weeks or more: The cells of the central nervous system adapt their metabolic apparatus to use ketone bodies in place of glucose. (Ketone bodies are substances synthesized by the liver as a step in the metabolism of fats.) The nerve cells obtain their needed functional energy from these metabolites. This explains why patients with blood sugar problems (diabetes or hypoglycemia) do not suffer ill effects during a fast. In fact, they benefit by fasting. (This topic will be discussed in depth in a later lesson.)
==== Carbohydrates Provide Fuel for the Muscular System ====
Carbohydrates provide the major fuel for muscular exercise. Fats and proteins can be used only indirectly—by first being converted into carbohydrates. For this reason, a proper diet should consist primarily of carbohydrates—not primarily of proteins and fats as are commonly consumed in conventional nonvegetarian (and some lacto- and lacto-ovo vegetarian) diets.
The muscles use the glycogen present in the muscle cells and glucose in the blood stream. However, glycogen from the muscles is more efficiently used than glucose because the breakdown of glycogen for use does not require energy input at the time, whereas a certain amount of energy is used to bring the blood sugar into the metabolic system of the muscles. (It does require energy to build up the glycogen supply in the first place, but this happens during periods of rest when plenty of energy is available.)
The muscles use the glycogen present in the muscle cells and glucose in the blood- stream. However, glycogen from the muscles is more efficiently used than glucose be- cause the breakdown of glycogen for use does not require energy input at the time, whereas a certain amount of energy is used to bring the blood sugar into the metabolic system of the muscles. (It does require energy to build up the glycogen supply in the first place, but this happens during periods of rest when plenty of energy is available.)
If a diet high in carbohydrates is not consumed, tremendous muscular exertion over long periods and/or extreme and prolonged stress (as being stranded for weeks in Antarctica) can result in accelerated breakdown of body protein and stored body fat. The protein breakdown is evidenced by an increased excretion of nitrogen in the urine, and the fat breakdown is evidenced by a rise in the level of ketone bodies in the urine and in the blood. The blood sugar level is simultaneously lower.
If a diet high in carbohydrates is not consumed, tremendous muscular exertion over long periods and/or extreme and prolonged stress (as being stranded for weeks in Antarctica) can result in accelerated breakdown of body protein and stored body fat. The protein breakdown is evidenced by an increased excretion of nitrogen in the urine, and the fat breakdown is evidenced by a rise in the level of ketone bodies in the urine and in the blood. The blood sugar level is simultaneously lower.
The body works much more efficiently from carbohydrate intake than from broken- down body protein and fats because protein and fat molecules, when used as fuel, yield less than their total caloric value in the form the muscles can use. The remaining portion is used for the conversion of these molecules into suitable fuel. This conversion takes place in the liver and adipose tissue, which supply the body’s organs with fuel via the bloodstream.
The body works much more efficiently from carbohydrate intake than from broken- down body protein and fats because protein and fat molecules, when used as fuel, yield less than their total caloric value in the form the muscles can use. The remaining portion is used for the conversion of these molecules into suitable fuel. This conversion takes place in the liver and adipose tissue, which supply the body’s organs with fuel via the bloodstream.
The fact that the body can and will use body fats and proteins when the supply and stores of blood sugar and glycogen are not great enough to meet the demand for energy exemplifies two facts: 1) The organism is provident. It has many back-up arrangements for survival in emergency situations when sufficient carbohydrates are not available. 2) An appropriate balance between supplying body needs (such as rest and carbohydrates) and expending energy (muscular, nervous or other) should be strived for to attain opti- mum health and well-being.
The fact that the body can and will use body fats and proteins when the supply and stores of blood sugar and glycogen are not great enough to meet the demand for energy exemplifies two facts: 1) The organism is provident. It has many back-up arrangements for survival in emergency situations when sufficient carbohydrates are not available. 2) An appropriate balance between supplying body needs (such as rest and carbohydrates) and expending energy (muscular, nervous or other) should be strived for to attain optimum health and well-being.
It has been found that people who are accustomed to doing prolonged or strenuous work have larger stores of glycogen (and of phosphate esters) in their muscles than those not accustomed to much physical activity. It is, therefore, beneficial to do regular vig- orous exercise to increase our storage of muscle glycogen. We will then be prepared to expend energy for longer and more strenuous exercise—whether it be in an emergency or in pursuing pleasure.
It has been found that people who are accustomed to doing prolonged or strenuous work have larger stores of glycogen (and of phosphate esters) in their muscles than those not accustomed to much physical activity. It is, therefore, beneficial to do regular vigorous exercise to increase our storage of muscle glycogen. We will then be prepared to expend energy for longer and more strenuous exercise—whether it be in an emergency or in pursuing pleasure.
==== Carbohydrates Supposedly Spare Proteins ====
Physiology textbooks refer to this so-called role or function of carbohydrate in the body as “its protein-sparing action.” However, it is incorrect to attribute action (other than chemical action) to carbohydrates or other inanimate substances. Besides, “sparing protein” is not a function or role of carbohydrates at all. Carbohydrates simply furnish our fuel or energy needs—and nothing more.
Physiology textbooks refer to this so-called role or function of carbohydrate in the body as “its protein-sparing action.” However, it is incorrect to attribute action (other than chemical action) to carbohydrates or other inanimate substances. Besides, “sparing protein” is not a function or role of carbohydrates at all. Carbohydrates simply furnish our fuel or energy needs—and nothing more.
In short, the so-called “protein-sparing action” of carbohydrates is not only not an action, but sparing proteins is not a distinct role of carbohydrates separate from their energy-providing role.
In short, the so-called “protein-sparing action” of carbohydrates is not only not an action, but sparing proteins is not a distinct role of carbohydrates separate from their energy-providing role.
==== Carbohydrates Supposedly Supply “Dietary Fiber” ====
“Dietary fiber” is a fairly new term coined to describe the cellulose inside plant cells. Cellulose is known to be indigestible by humans, though it is digested and used for energy by herbivores. The claims made about “the beneficial role of dietary fiber in preventing diseases” are so popular and so widely made that they are practically accepted as fact. However, cellulose, though in fact a carbohydrate because it is utilized as such by herbivores, does not serve the role of a carbohydrate in human physiology. Because it cannot be digested and utilized by humans, it cannot provide us with energy—and providing energy is the only role of carbohydrates in human nutrition.
“Dietary fiber” is a fairly new term coined to describe the cellulose inside plant cells. Cellulose is known to be indigestible by humans, though it is digested and used for en- ergy by herbivores. The claims made about “the beneficial role of dietary fiber in pre- venting diseases” are so popular and so widely made that they are practically accepted as fact. However, cellulose, though in fact a carbohydrate because it is utilized as such by herbivores, does not serve the role of a carbohydrate in human physiology. Because it cannot be digested and utilized by humans, it cannot provide us with energy—and pro- viding energy is the only role of carbohydrates in human nutrition.
The above statements may come as a surprise to most readers—but read on and we’ll clarify further.
The above statements may come as a surprise to most readers—but read on and we’ll clarify further.
It has been observed that certain so-called primitive tribes in Africa and elsewhere who consume diets high in fiber are less likely to develop certain colon diseases and metabolic disorders than their kinsmen who live in urban areas and eat low-fiber foods similar to those consumed in so-called developed countries. Based on the high corre- lation between low-fiber diets and human gastrointestinal diseases, many hospitals and clinics have changed their dietary management of diverticulosis. They are experiencing good results with a diet containing more instead of less cellulose.
It has been observed that certain so-called primitive tribes in Africa and elsewhere who consume diets high in fiber are less likely to develop certain colon diseases and metabolic disorders than their kinsmen who live in urban areas and eat low-fiber foods similar to those consumed in so-called developed countries. Based on the high correlation between low-fiber diets and human gastrointestinal diseases, many hospitals and clinics have changed their dietary management of diverticulosis. They are experiencing good results with a diet containing more instead of less cellulose.
We do not deny that high-fiber diets are more wholesome as a rule than low-fiber di- ets, nor do we deny the fact that people who consume diets closer to nature and therefore higher in fiber (cellulose) have fewer gastrointestinal diseases and a lower rate of bowel cancer. What we argue against is the thinking that the fiber itself is primarily responsible for the prevention of these diseases and disorders.
We do not deny that high-fiber diets are more wholesome as a rule than low-fiber diets, nor do we deny the fact that people who consume diets closer to nature and therefore higher in fiber (cellulose) have fewer gastrointestinal diseases and a lower rate of bowel cancer. What we argue against is the thinking that the fiber itself is primarily responsible for the prevention of these diseases and disorders.
Since cellulose is indigestible, it cannot be utilized by the body as a nutrient. It is simply passed through with the other wastes. Its presence or absence in the feces is in- significant. What is significant is how much and what kinds of toxins are there (and else- where). The ingestion of too many toxins from all sources, as well as the retention of toxic wastes produced within the body, results in diseases. The presence or absence of indigestible plant fibers does not prevent or cause diseases.
Since cellulose is indigestible, it cannot be utilized by the body as a nutrient. It is simply passed through with the other wastes. Its presence or absence in the feces is insignificant. What is significant is how much and what kinds of toxins are there (and elsewhere). The ingestion of too many toxins from all sources, as well as the retention of toxic wastes produced within the body, results in diseases. The presence or absence of indigestible plant fibers does not prevent or cause diseases.
Processed, highly-refined, so-called foods (they do contain carbohydrates) do not deserve the label foods because they are not whole foods. Parts of processed foods are missing—they were removed intentionally in the refining process. (Fiber [cellulose] is one of those missing parts.) This makes them incomplete or fragmented foods. Eating fragmented foods results in problems in the body. Therefore, they should not be eaten.
Processed, highly-refined, so-called foods (they do contain carbohydrates) do not deserve the label foods because they are not whole foods. Parts of processed foods are missing—they were removed intentionally in the refining process. (Fiber [cellulose] is one of those missing parts.) This makes them incomplete or fragmented foods. Eating fragmented foods results in problems in the body. Therefore, they should not be eaten.
Refined sugar and products containing refined sugar, as well as refined flour prod- ucts, are the most salient examples of processed food fragments that produce toxic ef- fects in the body. Being devoid of vitamins and minerals in their natural form (the only
Refined sugar and products containing refined sugar, as well as refined flour products, are the most salient examples of processed food fragments that produce toxic effects in the body. Being devoid of vitamins and minerals in their natural form (the only
form they can be used in), these products are like drugs within the body. In addition, calcium and other minerals, as well as B vitamins, must be utilized by the body to me- tabolize refined products. Because the refined products are devoid of nutrients except carbohydrates, calcium is taken from the bones.
form they can be used in), these products are like drugs within the body. In addition, calcium and other minerals, as well as B vitamins, must be utilized by the body to metabolize refined products. Because the refined products are devoid of nutrients except carbohydrates, calcium is taken from the bones.
Most “civilized” diets contain cooked foods, foods not normal to humans, refined and processed foods and drugs and medications. Refined sugar, flours, white rice and processed cereals are some of the worst culprits, but there are many, many more sources of toxins in the diet. Also, incompatible food combinations result in the production of toxins in the stomach and elsewhere in the digestive tract, and these toxins also contrib- ute to gastrointestinal disturbances and diseases.
Most “civilized” diets contain cooked foods, foods not normal to humans, refined and processed foods and drugs and medications. Refined sugar, flours, white rice and processed cereals are some of the worst culprits, but there are many, many more sources of toxins in the diet. Also, incompatible food combinations result in the production of toxins in the stomach and elsewhere in the digestive tract, and these toxins also contribute to gastrointestinal disturbances and diseases.
Much more could be said about the sources of toxins within the body that result in disease, but this has been discussed in previous lessons and will also be further discussed in future lessons. For now, it is sufficient for us to explain that low-fiber diets not on- ly lack the natural cellulose which should be left intact in the whole food, but they also contain or give rise to a host of toxins that result in disease conditions. It is not the lack of fiber itself that causes diverticulosis and other gastrointestinal problems but the over- all unwholesomeness of the foods ingested in so-called civilized society. (Of course, you should understand that what is eaten is only part of the picture and that how it’s eaten, how much is eaten, the amount of exercise, sleep, fresh air, etc., indulged are also im- portant factors in human nutrition.)
Much more could be said about the sources of toxins within the body that result in disease, but this has been discussed in previous lessons and will also be further discussed in future lessons. For now, it is sufficient for us to explain that low-fiber diets not only lack the natural cellulose which should be left intact in the whole food, but they also contain or give rise to a host of toxins that result in disease conditions. It is not the lack of fiber itself that causes diverticulosis and other gastrointestinal problems but the over- all unwholesomeness of the foods ingested in so-called civilized society. (Of course, you should understand that what is eaten is only part of the picture and that how it’s eaten, how much is eaten, the amount of exercise, sleep, fresh air, etc., indulged are also important factors in human nutrition.)
=== How Carbohydrates Are Digested And Used By The Body ===
7.4.1 Introduction to Digestion
7.4. How Carbohydrates Are Digested And Used By The Body
7.4.2 Salivary Carbohydrate Digestion
7.4.1 Introduction to Digestion
7.4.3 Starch Digestion in the Intestine
7.4.4 Carbohydrate Absorption
7.4.5 Carbohydrate Metabolism
7.4.5 Carbohydrate Metabolism
7.4.6 Sources of Glucose
7.4.6 Sources of Glucose
7.4.7 Regulation of Blood Glucose Concentration 7.4.8 How Energy is Derived From Glucose
7.4.7 Regulation of Blood Glucose Concentration
7.4.8 How Energy is Derived From Glucose
7.4.9 Carbohydrates in Relation to Other Nutrients
7.4.9 Carbohydrates in Relation to Other Nutrients
==== Introduction to Digestion ====
Before discussing carbohydrate digestion in particular, let’s give a little attention to digestion in general. Complete and thorough digestion of foodstuffs is extremely important for good health. A tremendous amount of toxin elimination and accumulation puts a great stress and burden upon the organism and results in a large variety and number of diseases. This happens both directly, from the presence of accumulated toxic substances that the body was unable to eliminate, and indirectly, from a decrease in the body’s digestive capabilities due to overworking the digestive system and depleting the body’s supply of vital energy.
It is, therefore, important for us to do everything we can to insure thorough and complete digestion of all foods eaten. This can be done by eating primarily (or only) easily digested and uncomplicated foods such as fruits; by eating compatible combinations of foods; by eating moderate amounts of foods; by eating at well-spaced meals; by abstain- ing from drinks during or too soon before or after meals; and by refraining from eating while under stress or emotionally upset.
One of two things happens to foods that do not get thoroughly or completely digested:
1) Sugars may ferment or 2) proteins may putrefy (rot). These processes result from bacterial activity which breaks down (decomposes) undigested or undigestible foods in preparation for their elimination from the body. The “trick” to, getting nourishment (nutriment) from the foods you eat is to see to it that they, get digested quickly, before the bacteria (present within every healthy digestive tract) have a chance to decompose them. The results of bacterial decomposition are toxic and do not provide nourishment. Foods that don’t digest relatively soon after ingestion will ferment or putrefy and contribute to body toxicity and disease.
Keeping the above facts about digestion in mind, let’s take a look now at carbohydrate digestion.
==== Salivary Carbohydrate Digestion ====
Disaccharides and polysaccharides must be digested before the body can use them, while monosaccharides do not require digestion. For this reason, as well as for other reasons (to be discussed in depth later in this lesson), our best source of carbohydrates is from fruits. Fruits require much less of the body’s energies and render primarily monosaccharides that, as stated, need no digestion.
Digestion is both a mechanical process (chewing) and a chemical process (enzymic actions). The class of enzymes that hydrolyze carbohydrates are broadly known as carbohydrases. We will be concerned in this lesson with carbohydrases known as amylases.
Digestion is both a mechanical process (chewing) and a chemical process (enzymic actions). The class of enzymes that hydrolyze carbohydrates are broadly known as car- bohydrases. We will be concerned in this lesson with carbohydrases known as amylases.
While the digestion of all types of foods (proteins, carbohydrates, fats, etc.) begins in the mouth with the mechanical process of mastication, certain carbohydrates—namely, starches and dextrins—are the only food types whose chemical digestion begins in the mouth. Here an enzyme known as salivary amylase or ptyalin, secreted by the parotid glands, is mixed with the food during the chewing process and begins the conversion of glycogen, starch and dextrins into the disaccharide maltose.
While the digestion of all types of foods (proteins, carbohydrates, fats, etc.) begins in the mouth with the mechanical process of mastication, certain carbohydrates—namely, starches and dextrins—are the only food types whose chemical digestion begins in the mouth. Here an enzyme known as salivary amylase or ptyalin, secreted by the parotid glands, is mixed with the food during the chewing process and begins the conversion of glycogen, starch and dextrins into the disaccharide maltose.
What happens when the starches, dextrin, and glycogens that were not converted to maltose in the mouth and what happens to the maltose when these carbohydrates reach the stomach depends upon several factors—what other types of foods are eaten with the starch, how much food is being eaten and how fast, the emotional condition of the eater and the condition of the eater’s digestive system. If a relatively uncomplicated starch such as potatoes or yams is eaten alone or with nonstarchy vegetables, and no proteins (as meats, cheese or milk, or even nuts or seeds or acids (as tomatoes, lemon or lemon juice or vinegar—as in salads or salad dressings) are consumed with the starchy food, salivary amylase (ptyalin) can and will continue the digestion of starches and dextrins in the stomach for a long period.
What happens when the starches, dextrin, and glycogens that were not converted to maltose in the mouth and what happens to the maltose when these carbohydrates reach the stomach depends upon several factors—what other types of foods are eaten with the starch, how much food is being eaten and how fast, the emotional condition of the eater and the condition of the eater’s digestive system. If a relatively uncomplicated starch such as potatoes or yams is eaten alone or with nonstarchy vegetables, and no proteins (as meats, cheese or milk, or even nuts or seeds or acids (as tomatoes, lemon or lemon juice or vinegar—as in salads or salad dressings) are consumed with the starchy food, salivary amylase (ptyalin) can and will continue the digestion of starches and dextrins in the stomach for a long period.
For thorough digestion and consequent good health, this continuation of starch di- gestion by ptyalin in the stomach is a necessity. Therefore, for good health, it is impor- tant to consume starchy foods at separate meals from protein foods and acids. (This and other facts relative to the topic of food combining for good digestion will be discussed in depth in later lessons.)
For thorough digestion and consequent good health, this continuation of starch digestion by ptyalin in the stomach is a necessity. Therefore, for good health, it is important to consume starchy foods at separate meals from protein foods and acids. (This and other facts relative to the topic of food combining for good digestion will be discussed in depth in later lessons.)
Briefly stated, ingestion of protein foods causes a secretion of hydrochloric acid in the stomach, and hydrochloric acid destroys ptyalin; that is, it destroys the amylase ac- tivity and substitutes acid hydrolysis. Physiology texts state that “if this acid hydrolysis was continued long enough it could reduce all the digestible carbohydrates to the mono- saccharide stage. However, the stomach empties itself before this can take place.”
Briefly stated, ingestion of protein foods causes a secretion of hydrochloric acid in the stomach, and hydrochloric acid destroys ptyalin; that is, it destroys the amylase activity and substitutes acid hydrolysis. Physiology texts state that “if this acid hydrolysis was continued long enough it could reduce all the digestible carbohydrates to the monosaccharide stage. However, the stomach empties itself before this can take place.”
The acids of tomatoes, berries, oranges, grapefruits, lemons, limes, pineapples, sour grapes and other sour fruits and the acid of vinegar will, like hydrochloric acid, destroy our only starch-splitting enzyme, ptyalin. Therefore, these foods also inhibit starch di- gestion. For good digestion and consequent good health, acids should not be eaten at the same meal with starches.
The acids of tomatoes, berries, oranges, grapefruits, lemons, limes, pineapples, sour grapes and other sour fruits and the acid of vinegar will, like hydrochloric acid, destroy our only starch-splitting enzyme, ptyalin. Therefore, these foods also inhibit starch digestion. For good digestion and consequent good health, acids should not be eaten at the same meal with starches.
Another factor that can impair salivary starch digestion is the drinking of water or other liquids with or too soon before or after meals. Water or other liquids do not aid in the digestion of foods. On the contrary, they interfere with digestion by diluting the di- gestive juices and cause them and their enzymes to be passed through the digestive tract too quickly for digestion to occur.
Another factor that can impair salivary starch digestion is the drinking of water or other liquids with or too soon before or after meals. Water or other liquids do not aid in the digestion of foods. On the contrary, they interfere with digestion by diluting the digestive juices and cause them and their enzymes to be passed through the digestive tract too quickly for digestion to occur.
To summarize this aspect of starch digestion, taking proteins, acids, water or other liquids with starches interferes seriously with their digestion by the salivary amylase, ptyalin. This first stage of starch digestion is of great importance because there is a great likelihood that the food will be acted upon by bacteria and ferment before it reaches the intestine where further starch digestion can take place. Digestion, rather than fermenta- tion and its resulting toxic byproducts, is much more likely to occur soon after the food is put into the mouth than further along in the digestive tract.
To summarize this aspect of starch digestion, taking proteins, acids, water or other liquids with starches interferes seriously with their digestion by the salivary amylase, ptyalin. This first stage of starch digestion is of great importance because there is a great likelihood that the food will be acted upon by bacteria and ferment before it reaches the intestine where further starch digestion can take place. Digestion, rather than fermentation and its resulting toxic byproducts, is much more likely to occur soon after the food is put into the mouth than further along in the digestive tract.
From the above, you can see why thorough mastication of food is so important when starches are eaten. No one who seeks health should eat starches in a hurry, nor should they have them with a beverage or with proteins or acids, for good digestion of foods is imperative for good health.
From the above, you can see why thorough mastication of food is so important when starches are eaten. No one who seeks health should eat starches in a hurry, nor should they have them with a beverage or with proteins or acids, for good digestion of foods is imperative for good health.
A special note should be made here about glycogen—animal starch. Glycogen should not be consumed by health seekers because much disease results from the inges- tion of animal flesh and animal products. This will be discussed in depth in later lessons. For the purposes of this lesson, suffice it to say that glycogen ingested cannot be digest- ed in the stomach because, of the hydrochloric acid that will be secreted to digest the protein, which is the primary nutritive component of foods that contain glycogen. There- fore, whatever glycogen that is not converted to a disaccharide by the salivary amylase, ptyalin, must be converted in the intestine. The likelihood of the glycogen reaching the intestine without fermenting before it can get there is small. This is just one of the many hazards of consuming animal flesh and animal foods.
A special note should be made here about glycogen—animal starch. Glycogen should not be consumed by health seekers because much disease results from the ingestion of animal flesh and animal products. This will be discussed in depth in later lessons. For the purposes of this lesson, suffice it to say that glycogen ingested cannot be digest- ed in the stomach because, of the hydrochloric acid that will be secreted to digest the protein, which is the primary nutritive component of foods that contain glycogen. Therefore, whatever glycogen that is not converted to a disaccharide by the salivary amylase, ptyalin, must be converted in the intestine. The likelihood of the glycogen reaching the intestine without fermenting before it can get there is small. This is just one of the many hazards of consuming animal flesh and animal foods.
==== Starch Digestion in the Intestine ====
Now that we have discussed starch digestion by the enzyme ptyalin, let’s get into starch and sugar (disaccharide) digestion in the intestine.
Now that we have discussed starch digestion by the enzyme ptyalin, let’s get into starch and sugar (disaccharide) digestion in the intestine.
At this stage in the digestive process, that is, after the polysaccharides (starch, dex- trin and glycogen) have been converted to the disaccharide maltose, maltose and the oth- er disaccharides (sucrose and lactose) must be converted to monosaccharides since, as stated earlier, the body can absorb and use sugars only as monosaccharides. This is ac- complished by the amylases maltase (to convert maltose), sucrase (to convert sucrose) and lactase (to convert lactose). These amylases are secreted by the wall of the small in- testine and are capable of splitting the particular sugars for which they were designed to the monosaccharide stage.
At this stage in the digestive process, that is, after the polysaccharides (starch, dex- trin and glycogen) have been converted to the disaccharide maltose, maltose and the oth- er disaccharides (sucrose and lactose) must be converted to monosaccharides since, as stated earlier, the body can absorb and use sugars only as monosaccharides. This is ac- complished by the amylases maltase (to convert maltose), sucrase (to convert sucrose) and lactase (to convert lactose). These amylases are secreted by the wall of the small in- testine and are capable of splitting the particular sugars for which they were designed to the monosaccharide stage.
==== Carbohydrate Absorption ====
Even though some substances (water, ethyl alcohol, small amounts of monosaccha- rides) may be absorbed into the bloodstream through the mucosa (mucous membrane) of the stomach, most absorption of the soluble products of digestion occurs in the small intestine. There the absorptive surface is increased about 600 times by villi, which are fingerlike projections in the lining of the small intestine. Each individual villus contains a network of capillaries surrounding a lymph vessel, and each cell on the surface of the villus is made up of smaller units called brush border cells or micro villi.
Even though some substances (water, ethyl alcohol, small amounts of monosaccha- rides) may be absorbed into the bloodstream through the mucosa (mucous membrane) of the stomach, most absorption of the soluble products of digestion occurs in the small intestine. There the absorptive surface is increased about 600 times by villi, which are fingerlike projections in the lining of the small intestine. Each individual villus contains a network of capillaries surrounding a lymph vessel, and each cell on the surface of the villus is made up of smaller units called brush border cells or micro villi.
Active transport is the osmotic process used when substances or nutrients are ab- sorbed from an area of lower concentration across a membrane to an area of higher con- centration. This process requires energy for the absorption, as well as a “carrier” to trans- port the substance. The carrier substance is thought to be a protein or lipoprotein (a com- bination of a protein and a fat). Glucose and galactose are absorbed into the bloodstream by active transport. Monosaccharides are absorbed by the capillaries, which empty into the portal vein, which in turn carries them directly to the liver.
Active transport is the osmotic process used when substances or nutrients are ab- sorbed from an area of lower concentration across a membrane to an area of higher con- centration. This process requires energy for the absorption, as well as a “carrier” to trans- port the substance. The carrier substance is thought to be a protein or lipoprotein (a com- bination of a protein and a fat). Glucose and galactose are absorbed into the bloodstream by active transport. Monosaccharides are absorbed by the capillaries, which empty into the portal vein, which in turn carries them directly to the liver.
==== Carbohydrate Metabolism ====
Metabolism is the term used to describe the many chemical changes that occur after the end products of digestion have been absorbed into the body. There are two phases of metabolism: 1) anabolism, which is the chemical reaction by which absorbed nutrients are utilized for replacement of used or worn-out body substances (maintenance) and to create new cellular material (growth), and 2) catabolism, which includes the chemical reactions whereby cellular materials are broken down into smaller units. An example of anabolism is the use of monosaccharides to build up stores of muscle and liver glycogen, and an example of catabolism is the breaking down of these glycogen stores to supply energy to the muscles during physical exersion. Anabolism and catabolism occur simul- taneously in the body cells.
Metabolism is the term used to describe the many chemical changes that occur after the end products of digestion have been absorbed into the body. There are two phases of metabolism: 1) anabolism, which is the chemical reaction by which absorbed nutrients are utilized for replacement of used or worn-out body substances (maintenance) and to create new cellular material (growth), and 2) catabolism, which includes the chemical reactions whereby cellular materials are broken down into smaller units. An example of anabolism is the use of monosaccharides to build up stores of muscle and liver glycogen, and an example of catabolism is the breaking down of these glycogen stores to supply energy to the muscles during physical exersion. Anabolism and catabolism occur simul- taneously in the body cells.
==== Sources of Glucose ====
The body’s immediate needs determine whether carbohydrates that have been di- gested and absorbed are used for immediate energy, converted and stored as glycogen or changed to fat and stored in adipose tissue.
The body’s immediate needs determine whether carbohydrates that have been di- gested and absorbed are used for immediate energy, converted and stored as glycogen or changed to fat and stored in adipose tissue.
4. Fromnoncarbohydratesources.Ifthebodycellsrequiremoreenergythancanbesup- plied by glucose and glycogen reserves, noncarbohydrate sources can be used to supply glucose. The noncarbohydrate sources used include certain amino acids from protein, glycerol from fat and, indirectly, fatty acids from fat.
4. Fromnoncarbohydratesources.Ifthebodycellsrequiremoreenergythancanbesup- plied by glucose and glycogen reserves, noncarbohydrate sources can be used to supply glucose. The noncarbohydrate sources used include certain amino acids from protein, glycerol from fat and, indirectly, fatty acids from fat.
==== Regulation of Blood Glucose Concentration ====
The liver, the pancreas and the adrenal glands play roles in keeping the blood sugar level at a normal concentration of around 90 mg. per 100 ml.
The liver, the pancreas and the adrenal glands play roles in keeping the blood sugar level at a normal concentration of around 90 mg. per 100 ml.
Three hormones are involved in increasing the concentration of glucose in the blood when necessary: norepinephrine, epinephrine and glucagon. Norepinephrine and epi- nephrine are secreted by the adrenal glands and glucagon is secreted by the pancreas. These hormones cause liver glycogen to split into glucose, which is then emptied into the blood. This returns the blood glucose concentration back toward normal.
Three hormones are involved in increasing the concentration of glucose in the blood when necessary: norepinephrine, epinephrine and glucagon. Norepinephrine and epi- nephrine are secreted by the adrenal glands and glucagon is secreted by the pancreas. These hormones cause liver glycogen to split into glucose, which is then emptied into the blood. This returns the blood glucose concentration back toward normal.
==== How Energy is Derived From Glucose ====
Energy is derived from glucose in one of two basic ways: 1) by oxidation and 2) by glycolysis. By far the major amount of energy from glucose is released in a series of re- actions in the cells in the presence of oxygen; but some energy from glucose is released by a process called glycolysis. This is an involved process which does not require the presence of oxygen. (A detailed explanation can be found in a physiology text such as Physiology of the Human Body by Arthur C. Guyton, M.D.)
Energy is derived from glucose in one of two basic ways: 1) by oxidation and 2) by glycolysis. By far the major amount of energy from glucose is released in a series of re- actions in the cells in the presence of oxygen; but some energy from glucose is released by a process called glycolysis. This is an involved process which does not require the presence of oxygen. (A detailed explanation can be found in a physiology text such as Physiology of the Human Body by Arthur C. Guyton, M.D.)
==== Carbohydrates in Relation to Other Nutrients ====
Not only are fats converted to carbohydrates for energy when carbohydrate intake is inadequate, but when carbohydrates are consumed beyond need, the excess is converted to fat and stored in adipose tissue. Also, the B-complex vitamins and the mineral calci- um are known to play an integral part in carbohydrate metabolism.
Not only are fats converted to carbohydrates for energy when carbohydrate intake is inadequate, but when carbohydrates are consumed beyond need, the excess is converted to fat and stored in adipose tissue. Also, the B-complex vitamins and the mineral calci- um are known to play an integral part in carbohydrate metabolism.