However, it was not until 1839 that basic cell theory, as we know it today, was formulated. In that year the German botanist Matthias Schlieden and the German zoologist Theodor Schwann proposed that all living organisms, plant and animal, were made of cells and cell products. Thus, the biology of a whole organism could be understood through a study of its cells. The German pathologist Rudolf Virchow completed cell theory nineteen years later by proposing that the entire body is composed of cells and cell products. This led to an understanding of cell division and differentiation.

On a parallel track, a literal explosion of knowledge occurred in physiology in the seventeenth century, beginning with the discovery of circulation of the blood, in 1616, by the English physician William Harvey. This was followed by rapid advances in the understanding of the functions of the various body organs. Knowledge which we take for granted, for example, the purpose of the liver, the kidneys and the pancreas, was unknown before physiologists Marcello Malpighi of Italy and Regnier de Graaf of Holland illuminated the scientific world with their pioneering research. The existence of oxygen and the utility it has for living organisms simply was unknown before the work of John Mayow. The average man on the street today knows more about cellular physiology than the greatest scientist living in the sixteenth century.

Let me refresh your memory and perhaps add some new facts to what you know. The physiology of any living organism — your body, for example — is a dynamic interplay between anabolism (buildup) and catabolism (breakdown). Your body requires constant sources of fuel: oxygen and food. While oxygen is obtained through the lungs and taken in directly, food is broken down into the simple building blocks of life: single molecules of fat, sugar and protein. These simple building blocks are called fatty acids, sugars (also called the -oses — glucose, fructose, maltose, etc.) — and amino acids.

This job is done by your digestive system, which includes your stomach, small intestine, large intestine, liver and pancreas. These single molecules enter your body by passing through the single layer of cells which lines your intestinal tract. This single layer of cells is designed to prevent the entry of anything more complex than a single molecule. Even sucrose, a simple combination of two simpler sugars, must be broken into its individual components before entry can be made into your body. The exceptions to these comments are some small polypeptides (two and three amino acids each) and a small amount of emulsified fat, which enter the body without complete breakdown.

Until molecules cross the single layer of cells which line the gut, they are outside your body, even though they are inside your intestinal tract.

Once access is gained to the body, these molecules are whisked around your body through your cardiovascular system by the action of your heart, and through the lymphatic system in the case of incompletely digested fat. The lymphatic system empties into the vascular system at the aorta, the large vessel coming out of the heart. Each living cell in your body is in direct contact with the cardiovascular system by circulation through the capillaries, so that these nutritive molecules can be collected by each cell on an as-need basis.

The real action is happening inside your cells. This is where the process happens which can most accurately be described as "life." Thanks to Schlieden and Schwann, we know that who we are at the biological level is a collection of individual cells. These cells are incredibly different from each other, specialized for particular jobs. However, they all have one thing in common: if they are alive, they are engaged in anabolism and catabolism — they are building up and breaking down — both processes at the same time.

The most important thing to know about a cell is that it wears a coat. This coat is known as the "plasma membrane." The plasma membrane is a continuous double layer of phospholipid molecules 75 to 100 angstroms thick. What makes life possible is that the plasma membrane is selectively permeable. It permits the exchange of molecules and atoms in and out of the cell, but on a selective basis. No molecule can come in or out without permission from the plasma membrane. This allows the cell to regulate its metabolism for its own purposes.

The most amazing thing about any cell in your body is that it works for the good of the entire organism. If it must lay down its life and die, so that the whole organism can live, it will. Your white blood cells are willing kamikaze warriors to combat any threat of infection by invading organisms. This characteristic of cells hints at the presence of an organizing intelligence living in the blood and sinews of your body, a soul.

There is much to be said about cells. I could tell you about the nucleus, the nucleolus, the nuclear envelope, the smooth endoplasmic reticulum, mitochondria, centrioles, Golgi bodies, liposomes, ribosomes and on and on. Perhaps I don't need to. You are cells. Your health depends on how well you take care of your cells.

Here is what you need to know regarding fasting. Catabolism creates waste products. These waste products are mixed into the cell soup, the cytoplasm, of the cell. For life to go on and vital health to happen, these waste products must be transported out of the body. The plasma membrane has the task of allowing these substances — principally carbon dioxide, urea and uric acid — to leave the cell, so that they can be picked up by the circulatory system and transported to the lungs (in the case of carbon dioxide), and to the skin, kidneys and intestines (in the case of urea and uric acid), where they leave the body.

Here resides the problem. The plasma membrane of each cell can somehow sense the concentration of toxic wastes in the circulatory system. If this concentration is above legal limit, the plasma membrane denies an exit visa for toxic wastes inside the cell until conditions outside the cell improve. When we overload our bodies with food, even if we are able to burn it up without gaining weight, we create a chronic condition of low grade toxemia.

Each cell becomes a storage unit for unusable, toxic molecules. This is not what a doctor would call "toxemia," because it is not life-threatening. However, if what you are interested in is the most health and vitality possible for you, this is definitely a chronic condition of low grade toxemia. Only children who are on a health supporting diet are immune from a chronic condition of low grade toxemia. All adults are suffering from this condition in some degree. The result is chronic, intermittent headache (look at the sales figures for over-the-counter headache remedies), or fatigue (take some No Doz, drink some tea or coffee), or arthritis (not natural to old age, but have a drug anyway), or irritability of the nervous system (have a tranquilizer), or insomnia (take a sleeping pill or drink some special herb tea —  more enlightened)...and so on. Each pill you take adds to the total load of toxic wastes your cells must bear, and compounds the problem in the long run. Even people who have regular colon irrigation and eat the right foods can still be full of, well, toxic wastes.

Now the stage is set for fasting, for when we admit to the possibility that we may be in a condition of chronic low grade toxemia, the next question is "What can we do about it?" The answer: fast. Only when this state of knowledge is reached can we rationally consider the benefits of fasting from a scientific point of view.

Notice I said scientific, not medical. The mind set which doctors live in is: treatment of illness, once it is firmly established and obvious. Your doctor is the wrong person to talk to regarding a condition of maximum vitality or even regarding prevention of illness. Blue Cross cannot be billed for that, not yet anyway. Therefore, your physician is unlikely to know anything about the benefits of fasting, and when physicians find themselves not knowing about something (which is intolerable to a doctor's ego), you can be sure they will make up an opinion, usually a negative one.

Fasting creates a condition of low concentration of toxic wastes in the circulatory system. This is sensed by the plasma membrane of each cell and each cell will then let go of its load of toxic wastes. When this happens suddenly, as it does with fasting, the result can be a sudden case of mild systemic toxemia as the system cleanses itself. Those who fast must be prepared for a phase of headache, irritability, insomnia and fatigue. This is a natural part of the healing process and should be welcomed. How long a person should fast is an individual matter. A thorough cleansing will require at least a few days. A week-long fast will get the job done for most people. The fast should not end until the symptomatic phase (headache, fatigue, etc.) is finished by at least two days. Any fast should be supervised by a doctor experienced in fasting. Generally speaking, these doctors practice nutritional medicine.

Any degree of overloading your body with food results in the intracellular collection of waste products. Fasting allows you to tip the scales in the other direction, so that your body can release itself from this condition of autointoxication.

Let me underline one point: the addiction to quantity of food as measured in calories. This is the item which creates the conditions which make fasting a useful tool. Addiction to quantity of food, as measured in calories, is the condition in which we live, it is almost the air we breathe, certainly it is the paradigm with which we unconsciously think about and experience hunger. You may not think you are addicted. You may be slim and exercise regularly, and yet you are addicted to quantity of food as measured in calories. Try making it on 2000 calories per day, and you will discover an awareness of your addiction.