FREE RADICALS – ANTIOXIDANTS**
Understanding these commonly used terms.
What are ‘Free Radicals’?
To answer this question, a brief refresher course in chemistry and physiology is necessary.
The human body is composed of trillions of cells of many different types. Cells are composed of many, many different types of molecules. Molecules consist of one or more atoms or one or more elements joined by chemical bands.
An atom consists of a nucleus, neutrons, protons and electrons.
A proton, which is a positively charged particle, exists in the atom’s nucleus.
An electron is a negatively charged particle, and the number of protons in the nucleus determines the number of electrons surrounding the atom (protons = electrons).
Electrons surround, or ‘orbit’, an atom in one or more shells. The innermost shell is full when it has two electrons. When the first shell is full (two electrons), electrons begin to fill the second shell. When the second shell has eight electrons, it is full, and so on.
Electrons are the substance that bonds atoms together to form molecules.
The number of electrons in the outer shell is the most important structural feature of an atom for determining its chemical behaviour. A substance that has a full outer shell (eight electrons) tends not to be involved in chemical reactions. This is an inert, or stable, substance.
Because atoms seek to reach a state of maximum stability, an atom will try to fill its outer shell by:
- Gaining, or losing electrons to either fill (eight) or empty (zero) its outer shell.
- Sharing its electrons by bonding together with other atoms in order to complete or fill its outer shell (eight, or two in the case of hydrogen).
Thus, atoms often complete their outer shells by sharing electrons with other atoms. By sharing electrons, the atoms are bound together and satisfy the conditions for maximum stability for the molecule.
- The hydrogen atom, H, has 1 proton and 1 electron. The first shell requires 2 for stability. Hence hydrogen in its stable form is a molecule, H2, made up of 2 hydrogen atoms, where each atom shares the other’s electron, thus filling the first shell.
- The oxygen atom, O, has 8 protons and 8 electrons (2 in the first or inner shell, and 6 in the outer shell). This second or outer shell requires 8 for stability. Hence oxygen in its stable form, as it exists for example in the air, is a molecule, O2, made of 2 oxygen atoms where each atom shares 2 electrons of the other atom, thus filling the second or outer shell.
- Water is H2O. The hydrogen molecule (H2) is stable. The atom oxygen, O, needs 2 electrons added to its outer shell for stability, which in this instance it receives from the H2, thus forming stable H2O. Valency is another way of expressing this: H+ + H+ + O═. Hydrogen has a positive one (H+) valency, oxygen a negative two (O═) valency.
- Ozone is O3: O2 + O. This molecule is unstable – the third O wants to separate, leaving the stable O2, and it joins up with another free O atom to form stable O2.
- Hydrogen peroxide is H2O2 or H2O + O, stable water with an extra atom of oxygen which is unstable. So it readily separates, leaving stable water, while the O joins with another oxygen atom to form stable O2.
Enough simple chemistry!
What, then, ARE free radicals and how are they formed?
A free radical is formed when a weak bond, ie shared electrons, splits. Normally, bonds (ie when electrons are shared by bonding together) do NOT split in a way that leaves a molecule with an odd, unpaired electron.
Free radicals, molecules with an odd, unpaired electron (no longer a full outer shell with 2 or 8 electrons), are very unstable and react quickly with other compounds, trying to capture the needed electron(s) to gain stability. Generally, free radicals attack the nearest stable molecule, ‘stealing’ an electron from it. When the “attacked” molecule loses its electron, it becomes a free radical itself, which in turn attacks another molecule, resulting in a chain reaction. This can lead to a cascade finally resulting in the disruption of a living cell.
Some free radicals arise normally as part of the metabolic processes continually going on in the human body. These free radicals can be regarded as chemical byproducts of normal cellular metabolism.
Apart from normal cellular metabolism resulting in free-radical formation, free radicals are also formed by environmental factors such as pollution (for example, car exhaust fumes), cigarette smoke (including second hand smoke), herbicides, pesticides and fungicides and other chemicals in the air we breath, the water we drink, and the plethora of chemicals in our foods such as colourings, flavourings, preservatives etc. Radiation, including ultraviolet radiation from the sun, is another cause of free-radical formation. Stress is yet another cause of free-radical formation.
Free radicals cause damage to many components of a cell, including the cell wall, the mitochondria and DNA. DNA is the highly complex molecule of which our genes are composed. When enough DNA is damaged, cells begin to die.
Free Radicals and Antioxidants
The formation of free radicals, and the damage they cause, can be likened to the process that occurs when an iron roof rusts. The iron in the roof is oxidized, and becomes iron oxide, that is, the iron joins (by sharing electrons) with oxygen to form stable iron oxide (rust). As this process continues, the iron will rust away, ie become fully oxidized, until no original iron remains.
This is why an iron roof can be protected by galvanising (adding zinc). Zinc is an ‘antioxidant’, that is, it protects and prevents oxidation, and hence prevents rusting and the destruction of the iron roof.
Another good example of oxygen free-radical damage can be seen when an apple is sliced in half and left exposed to air. Within a very short time, the apple begins to turn brown. This browning is caused by free-radical damage and will eventually destroy the fruit. It is for this reason that, when juicing fruits and vegetables using a juicer with the rotating plate, the juice should be consumed immediately, before significant oxidative (free-radical) damage takes place – in this instance to the whole fruit, which is exposed to oxygen as part of this type of juicing (refer to Chapter 8 in my book ‘How To Live to 100+ Years Free from Symptoms and Disease’, pages 75-79).
Free-radical damage is referred to as oxidation.
The substances which protect against free-radical damage (“oxidation”) in the body are called ‘antioxidants’.
Antioxidants neutralise free radicals by donating one of their own electrons, ending the electron ‘stealing’ reaction. The antioxidant nutrients themselves do not become free radicals by donating an electron, because they are stable in either form (with or without the donated electron). They act as scavengers, helping to prevent cell and tissue damage that could lead to cellular damage and disease.
The body produces its own protection against free-radical damage.
One of the best known of these is the enzyme SuperOxide Dismutase – S.O.D. This is a super-scavenger enzyme that ferrets out and destroys the free radicals. Hence S.O.D is called an antioxidant (enzyme). It protects against free radicals and they damage they may cause. It is of interest that Green Barley powder (see my Newsletter October 2006) contains S.O.D.
Other naturally occurring antioxidant enzymes are catalase and glutathioneperoxidase. However, S.O.D. is considered the most powerful of these enzymatic antioxidants that break down free radicals.
There may be beneficial effects from some of the oxidation. For example, it can destroy harmful bacteria and viruses in our body.
Normally, the body can completely deal with free radicals by the combined effect of the antioxidant enzymes such as S.O.D. and the antioxidants in our food or ingested as supplements (see below).
But if there is an inadequate production of the antioxidant enzymes and/or a deficient diet to neutralize the free radicals from metabolism and from the external causes (see above), then cellular damage may occur.
Overall, free radicals have been implicated in at least 50 diseases! A partial list includes heart disease, cancers, arthritis and other inflammatory diseases including bowel disease and colitis, cataracts and skin lesions. Free radical damage is the major factor of aging.
The body’s arsenal of antioxidants appears to be sufficient for keeping oxidation (free-radical damage) in check in children and in youths, but once we reach our twenties, the effectiveness of the body’s antioxidant defense mechanisms appears to lessen, and free radicals are given greater range to do damage. The results appear to be that many of the diseases we associate with aging, including coronary heart disease, cancer, skin damage, Alzheimer’s disease, strokes and arthritis are from free-radical damage.
Consuming more antioxidants helps provide the body with the means to neutralise harmful free radicals.
It is estimated that there are more than 4,000 compounds in foods that act as antioxidants. The most studied include vitamin A and betacarotente, vitamin C, vitamin E, the mineral selenium and the enzyme CoQ10.
Vitamin Food Sources of Antioxidants.
The most common and important antioxidants found in foods, and taken as supplements, are the vitamins A, C and E.
In order to understand these, and their role in combating free radicals and free-radical damage, it is helpful to look at what vitamins are.
What are Vitamins? An Overview.
The classic definition of vitamins states that vitamins are organic compounds, essential in the diet in small amounts, which are involved in fundamental functions of the body.
The word “vitamin” was coined in 1911 by the biochemist Casimir Funk (1884-1967). He isolated a substance that prevented nerve inflammation (neuritis) in chickens raised on a diet deficient in that substance. He named the substance “vitamine” because he believed it was necessary to life (vita) and that it was a chemical amine. The “e” at the end was later removed, when it was recognized that vitamins need not be amines.
It is generally accepted that there are 13 vitamins essential for healthy bodily functions. Vitamins A, C, D, E, K, the B vitamins (B1 thiamine, B2 riboflavin, B3 niacin, B5 pantothenic acid, B6 pyridoxine, B9 folate, B12 cobalamin) and biotin.
Except for vitamin D and vitamin K, vitamins cannot be manufactured by the body, they must all be obtained from food. Vitamin D and vitamin K can be synthesized by the body (vitamin D after exposure to UV sunlight).
Vitamins A, D, E and K are fat soluble.
Vitamin C, the B-complex vitamins and biotin are water soluble. These water soluble vitamins (except vitamin C) can be further classified into two groups according to their primary function in the body:
- those that are energy-releasing: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6) and biotin
- those that are haematopoietic (blood-cell-forming): cobalamin (B12) and folate (B9).
In this article, only the antioxidant vitamins well be discussed, namely vitamins A, C and E.
Vitamin A is a family of compounds that includes retinol, retinal and carotenoids. Retinol and retinal are potent forms of vitamin A that are commonly found in animal foods. Betacarotene, and the other 200 or so carotenoids, are commonly found in vegetables and are converted to vitamin A in the body. Vitamin A:
- Enhances the activity of the immune system
- Discourages the formation of abnormal cell growth by maintaining healthy cell membranes
- Is essential for normal eyesight
- Develops and maintains moist, healthy tissue throughout the entire body
- Is important in normal body growth and the formation of bones and soft tissue.
Animal food sources (vitamin A - retinol and retinal):
- Milk, cream, cheese
- Liver (very high), kidney
- Cod/halibut fish oils.
Because most are high in saturated fat and cholesterol, and are highly acid forming in the body, vegetable sources are a better choice, apart from cod liver oil.
Vegetable sources (betacarotene and the other carotenoids which are converted to vitamin A in the body):
- Dark leafy green vegetables such as spinach
- Yellow/orange vegetables such as carrots, pumpkin, sweet potatoes (kumera) (especially the red variety)
- Fruits such as rockmelon/cantaloupe, pink grapefruit, apricots, peaches, nectarines, water melon and pawpaw/papaya.
The more intense the colour of the fruit or vegetable, the higher the carotenoids and betacarotene content.
Vitamin C is an essential water-soluble vitamin that cannot be manufactured in the body. It is well respected for its antioxidant properties. Vitamin C:
- Aids in the formation and maintenance of collagen. This important protein forms the basis for connective tissue found throughout the body
- Is essential for the maintenance of bones, teeth, gums, collagen and blood vessels (capillaries)
- Acts as an antioxidant
- Stops the formation of cancer-causing nitrosamines and may slow the growth of cancer cells
- Helps regulate cholesterol metabolism in the liver and may lower LDL’s (bad cholesterol) and increase HDL’s (good cholesterol)
- Is essential for proper immune function.
Food Sources. Vitamin C is generally associated with bioflavinoids which enhance the bio-availability of this vitamin. It is found in:
- Fruits: citrus fruits and their juices, melons especially rockmelon/cantaloupe, kiwifruit, strawberries
- Vegetables: tomatoes, leafy greens such as spinach, broccoli, potatoes, sweet potato, capsicum/green and red peppers, cabbage and asparagus
- Most other fruits and vegetables contain some vitamin C
- Fish and milk contain small amounts.
Vitamin E is well knwon for its antioxidant activity. It consists of a family of fat-soluble materials that include tocopherols and tocotrienols. Alpha tocopherol is the most well known & researched. Vitamin E:
- Protects fats and vitamin A from free-radical destruction
- Exerts protective effects in all vital tissues, including the eyes, lungs, skin, heart and muscles
- Positively effects the immune system
- Defends red blood cells and may prevent hemolytic anemia.
- Vegetable oils
- Nuts and seeds
- Vegetables such as sweet potato, greens, asparagus and spinach
- Whole grain cereals
Non-Vitamin Food Sources of Antioxidants.
Apart from vitamins A, C and E, selenium, a mineral (trace element), has strong antioxidant properties, working synergistically with vitamin E. It is also a critical component of several cellular enzymes that protect red blood cells and cell membranes. It has clinical applications in many disease conditions.Selenium:
- Enhances the effectiveness of the immune system
- Keeps the immune system in balance with vitamin E.
- Seafoods (the majority), meats and eggs
- Plants: the selenium content varies depending on the selenium content of the soil
- Seeds (especially sunflower seeds) and whole grains.
CoQ10 is a fat soluble compound with several characteristics common to vitamins. It is an essential catalyst in the production of Adenosine Triphosphate (ATP), which helps transfer energy within the cell to drive various reactions. It has a long history of efficacious use as a therapeutic agent and antioxidant.
CoQ10 and CoQ compounds are widely distributed in all plants and animals. Like other vitamins, it is available as a supplement.
Other Important Protectors from Free Radicals
Zinc, Copper and Manganese, while not antioxidants in their own right, have a role in protecting against free-radical damage. They also have other important functions in the body which are not relevant in this discussion.
Zinc is an essential component of S.O.D and thus helps protect cells from free-radical damage.
Food sources include lean meats, oysters, poultry and whole grains and nuts.
Copper is also an important component of S.O.D.
Food sources include nuts, organ meats, poultry, shell fish, whole grains and dark leafy vegetables such as spinach.
Manganese is a constituent of another important antioxidant enzyme, Manganese Superoxide Dismutase (MnS.O.D).
Food sources include blueberries, pineapple, raisins, spinach and whole grains.
Supplement Sources of Antioxidants
For a discussion concerning vitamins to be taken as supplements, the reader is referred to chapter 11 of my book ‘How to Live to 100+ Years Free from Symptoms and Disease’ (pages 97-102). (see the homepage of this website)
** Copyright 2007: The Huntly Centre.Back to the list Print friendly version