Links between Redox Reactions and Cancer

Basically, reduction means the addition of an electron (e-), and its converse, oxidation means the removal of an electron. While the addition of an electron, reduction, stores energy in the reduced compound, the removal of an electron, oxidation, liberates energy from the oxidized compound. Whenever one substance is reduced, another is oxidized.  To clarify these terms we may consider any two molecules, A and B, for example and suppose that when molecules A and B come into contact, B grabs an electron from molecule A.  Molecule A has been oxidized because it has lost an electron.  The net charge of B has been reduced because it has gained a negative electron (e-).  In biological systems, removal or addition of an electron constitutes the most frequent mechanism of oxidation-reduction reactions. These oxidation-reduction reactions are frequently called redox reactions. 

Here an important question arises ‘can we afford to have too much of a good thing’?  Oxygen is essential to survival. It is relatively stable in the air, but when too much is absorbed into the body it can become active and unstable and has a tendency to attach itself to any biological molecule, including molecules of healthy cells. The chemical activity of these free radicals is due to one or more pairs of unpaired electrons. About 2% of the oxygen we normally breathe becomes active oxygen, and this amount increases to approximately 20% with aerobic exercise. 

Such free radicals with unpaired electrons are unstable and have a high oxidation potential, which means they are capable of stealing electrons from other cells. This chemical mechanism is very useful in disinfectants such as hydrogen peroxide and ozone which can be used to sterilize wounds or medical instruments. Inside the body these free radicals are of great benefit due to their ability to attack and eliminate bacteria, viruses and other waste products. 

Problems arise, however, when too many of these free radicals are turned loose in the body where they can also damage normal tissue.  Putrefaction sets in when microbes in the air invade the proteins, peptides, and amino acids of eggs, fish and meat. The result is an array of unpleasant substances such as:  hydrogen sulfide, ammonia, histamines, indoles, phenols, scatoles etc.

These substances are also produced naturally in the digestive tract when we digest food, resulting in the unpleasant odor evidenced in feces. Putrefaction of spoiled food is caused by microbes in the air; this natural process is duplicated in the digestive tract by intestinal microbes. All these waste products of digestion are pathogenic, that is, they can cause disease in the body.  Hydrogen sulfide and ammonia are tissue toxins that can damage the liver. Histamines contribute to allergic disorders such as atopic dermatitis, urticaria and asthma. Indoles and phenols are considered carcinogenic. 

 Because waste products such as hydrogen sulfide, ammonia, histamines, phenols and indoles are toxic, the body's defense mechanisms try to eliminate them by releasing neutrophils (a type of leukocyte, or white corpuscle). These neutrophils produce active oxygen, odd ball oxygen molecules that are capable of scavenging disintegrating tissues by gathering electrons from the molecules of toxic cells.  Problems arise, however, when too many of these active oxygen molecules, or free radicals, are produced in the body. They are extremely reactive and can also attach themselves to normal, healthy cells and damage them genetically.

These active oxygen radicals steal electrons from normal, healthy biological molecules. This electron theft by active oxygen oxidizes tissue and can cause disease. Because active oxygen can damage normal tissue, it is essential to scavenge this active oxygen from the body before it can cause disintegration of healthy tissue. If we can find an effective method to block the oxidation of healthy tissue by active oxygen, then we can attempt to prevent disease.

One way to protect healthy tissue from the ravages of oxidation caused by active oxygen is to provide free electrons to active oxygen radicals in order to neutralize their high oxidation potential and prevent them from reacting with healthy tissue.  Research on the link between diet and cancer is far from complete, but some evidences indicate that what we eat may affect our susceptibility to cancer. While some foods seem to help defend against cancer, others appear to promote it.  Much of the damage caused by carcinogenic substances in food may come about because of an oxidation reaction in the cell. In this process, an odd ball oxygen molecule may damage the cell's genetic code.

Some researchers believe that substances that prevent oxidation, called ANTIOXIDANTS, can block the damage. This leads naturally to the theory that the intake of natural antioxidants could be an important aspect of the body's defense against cancer. Substances that some believe inhibit cancer include vitamin C, vitamin E, beta-carotene, selenium, and glutathione (an amino acid). These substances are reducing agents. They supply electrons to free radicals and block the interaction of the free radical with normal tissue.