3. The Role Of Carbohydrates In The Body
Five subheadings follow in this lesson subdivision, but there is actually only one basic 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 satisfactorily 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.
3.1 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.
When carbohydrates needed for the functioning of the central nervous system, the muscles and the other body systems and functions are insufficient in the diet (as during a fast or on a weight-loss diet), stored adipose tissue (fat) is broken down into glucose to make up the caloric deficit. Some amino acids, instead of being used to make proteins, are deaminated and used as carbohydrates to supply energy. The formation of glucose from amino acids is called gluconeogenesis. This phenomenon enables one to maintain normal blood sugar levels during a fast.
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.
3.2 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.)
3.3 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 bloodstream. 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.)
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 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 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.
3.4 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.
What is being said in the textbooks is that proteins consumed will be used for tissue building and maintenance rather than being used as an emergency source of energy as long as the carbohydrate intake is sufficient. This is true, but it is only another way of saying that carbohydrates are the primary and most efficient source of energy or fuel and that it is best not to try to meet our fuel needs from proteins. It is stating the true fact that carbohydrates, not proteins, supply our primary nutrient needs.
“Sparing proteins” is not a separate and distinct function or role of carbohydrates any more than preventing scurvy is a separate and distinct function of vitamin C in the body. Vitamin C supplies body needs, but its role is not prevention of scurvy or of anything else. Viewing nutrients as preventative agents of diseases is another way of saying that diseases are normal, that they are an inevitable part of life that will and must occur unless prevented by the proper nutrients. That is a backwards way of viewing health—it’s the disease approach, or the medical approach. Just as good things happen to us if we think positive thoughts and visualize success, harmony, etc., good health will exist as long as we live healthfully—and that includes consuming the correct amounts of the foods to which we were biologically adapted in nature to eat.
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.
3.5 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.
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 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 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 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.
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 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 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 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 overall 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.)
- 1. Introduction
- 2. Classifications Of Carbohydrates
- 3. The Role Of Carbohydrates In The Body
- 4. How Carbohydrates Are Digested And Used By The Body
- 5. Sources Of Carbohydrates
- 6. Why Starches Are Less Than Ideal Sources Of Carbohydrates
- 7. Why Fruits Are The Ideal Source Of Carbohydrates
- 8. Amounts And Variety Of Carbohydrates Needed By Humans
- 9. Disease Conditions Related To Carbohydrate Consumption
- 10. Questions & Answers
- Article #1: Carbohydrates By Dr. Herbert M. Shelton
- Article #2: Digestion Of Foods By Dr. Herbert M. Shelton
- Article #3: Starches Are Second-Rate Foods By Marti Fry
- Article #4: The “Staff Of Life” By Marti Fry
- Article #5: What’s Wrong With Wheat By Marti Fry
- Article #6: Fruit – The Ideal Food By Dr. Herbert M. Shelton
- Article #7: Are Humans Starch Eaters? By Dr. Herbert M. Shelton