Neutralizing destructive free radicals is so important that God designed a unique and somewhat complicated system to protect us. This antioxidant network involves at least three tiers of protective molecules: (1) the vitamin, mineral and flavonoid network, (2) the antioxidant enzymes, and (3) special antioxidant molecules.
1) Vitamins, Minerals and Flavonoids
From extensive television advertising, most of us are familiar with vitamin antioxidants such as vitamin A, beta-carotene, vitamin C, and vitamin E. All are powerful antioxidants that neutralize a significant number of free radicals. Less well-known antioxidants are vitamins D and K, magnesium, zinc, and manganese. Also, there are over forty carotenoids and five thousand flavonoids from plants in the human diet that act as antioxidants.
Each antioxidant acts in a different place in the cells and tissues. For example, vitamin C is concentrated in the blood plasma, connective tissues, and within the cytoplasm of the cell. Vitamin E components are dissolved in the fatty parts of the cell such as the membranes and are not usually concentrated within the watery parts of the cell. Vitamin E is also an important part of the LDL cholesterol molecule. Carotenoids, such as beta-carotene, alpha-
carotene, lutein, and lycopene generally are found in the fatty parts of the cell as well, but can enter the watery cytosol of the cell. Minerals like zinc and magnesium are found principally within the cell.
So we see that this vitamin/mineral antioxidant network is highly compartmentalized so that each has its own zone of defense, much like football or basketball. This is another reason that all of the vitamins and minerals are needed in balance to adequately defend cells. Vitamin E's major role is to defend the membranes while magnesium, zinc, and other antioxidants primarily protect the DNA and cellular proteins. Vitamin C plays a major role in protecting the watery spaces both inside and outside the cell. Alpha-lipoic acid can go anywhere.
It should also be appreciated that this portion of the antioxidant system is highly dependent on our nutritional intake of preformed vitamins and minerals, even though some of the vitamins can be manufactured from other precursors, as in the case of vitamin A from beta-carotene.
When an antioxidant encounters a free radical it is oxidized and becomes a free radical itself, milder than the one it neutralized, but still capable of causing problems. This is why we have numerous types of antioxidants in our bodies, each one regenerates the other. For example, vitamin C regenerates vitamin E and visa versa. This is why it is a bad idea to take just one type vitamin, soon it will fill your body with an oxidized vitamin, causing more harm than good.
The rate at which our antioxidants are used up depends on how many free radicals we are producing. A person with lupus or diabetes will require considerably more antioxidants than a person who is perfectly healthy. An extreme athlete, likewise, will require more antioxidants than will a person who exercises moderately. From this you can see that a diabetic who takes no supplemental antioxidants and develops an infected toe is more likely to die from this event than is a diabetic who maintains an adequate store of antioxidants. Antioxidants must be constantly replenished, and a good diet and careful supplementation accomplish this goal.
Phytochemicals: the Flavonoids
Plants contain thousands of antioxidants, mostly in the form of specialized complex chemicals called flavonoids, each of which is a unique molecule that plays a major role in nutrition. Plants also contain numerous vitamins and minerals that act as antioxidants: one group of vitamins is called the carotenoids, which includes about forty different varieties that humans consume. Most of us have heard of beta-carotene, but there are others such as alpha carotene, lutein, lycopene, canthoxanthin, zeaxanthin, and cryptoxanthin. Diets poor in fruit and vegetable intakes deprive us of these vital antioxidants.
In 1936, a Nobel Prize-winning biochemist by the name of Szent-Gyorgi isolated a factor from plants that had some rather unusual properties. He knew that seriously depriving an animal of ascorbic acid would engender bleeding gums and internal bleeding, and that the animal would finally die as a result of extreme sensitivity to stress—a condition we know as scurvy. Yet when he fed the animals his newly discovered plant extract they appeared perfectly healthy, with no signs of scurvy, no matter how long they were denied vitamin C.
At the time, he felt his new factor met the criteria for a vitamin, and based on the idea that the new bioflavonoid inhibited the increased capillary permeability seen with vitamin C deficiency, he named it vitamin "P" for permeability factor. Later, biochemists concluded it was not a vitamin, and the compound was given the name bioflavonoid. Since this early discovery, thousands of flavonoid compounds have been discovered, many possessing quite unique biological properties.
Recent studies have demonstrated that all of these compounds are powerful and extremely versatile antioxidants, acting against a whole host of dangerous free radicals. In fact, some of the flavonoids can neutralize special free radicals that cannot be neutralized by most of the antioxidant vitamins and network enzymes. It should be noted that there are other dangerous radicals besides oxygen radicals. For example, there are reactive nitrogen species that can be equally, if not more, destructive than oxygen radicals. Vitamins are poor at neutralizing these special types of radicals, while flavonoids are very efficient.
In addition, several of the flavonoids can remove (chelate) dangerous, free-radical-generating metals, such as iron, copper, aluminum, and some of the heavy metals including mercury, arsenic, and lead. This becomes especially important as we age, since iron and aluminum accumulation is common with aging, and is also very common in neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease.
The antioxidant protection afforded by plant flavonoids makes sense when we realize that it is flavonoids and carotenoids that allow plants to survive in the glaring sun all day long. Normally, the sun's harsh rays would quickly destroy the leaves, but flavonoids block the damage, both by absorbing the harmful rays and by neutralizing the free radicals they generate. The same phenomenon occurs in humans.
Research into the medicinal properties of flavonoids has expanded almost exponentially in recent years. We are now finding that beyond their usefulness as antioxidants they may hold the key to controlling cancer, both as a preventative and as a treatment of established cancers.
2) Antioxidant Enzymes
The human body has several enzymes whose function it is to neutralize free radicals and other destructive oxidants. The first of these is superoxide dismutase or SOD. Actually there are three types of SOD: one associated with manganese, one with copper, and another with zinc, each of which has distinct locations and functions within the body. All function in converting the superoxide radical to hydrogen peroxide. Superoxide is a very destructive free radical and is found throughout the body. It has been estimated that over a lifetime we produce about three tons of superoxide radicals.
Deficiencies in zinc, copper, or manganese can result in malfunctions of these critical enzymes and can lead to serious disorders. For example, a deficiency in SOD in the spinal cord can result in a rare form of inherited amyotrophic lateral sclerosis. Stress is associated with an increased supply of SOD enzymes in the brain, as a reflexive protective mechanism.
When superoxide is converted into hydrogen peroxide, usually in the presence of free iron, all is still not well. If left alone the hydrogen peroxide can break down into the very destructive hydroxyl radical that can damage the cell's membranes and DNA, as well as other structures. It must be quickly neutralized to prevent irreversible damage. Two enzymes have the function of accomplishing this task: catalase and glutathione peroxidase, both of which convert hydrogen peroxide into harmless water. The brain contains very little catalase enzyme and is more dependent on the glutathione peroxidase enzyme. Deficiencies in either of these enzymes can lead to catastrophic diseases, as is seen with Parkinson's disease and possibly Alzheimer's dementia. Glutathione peroxidase enzyme is dependent on selenium.
Another important antioxidant enzyme is glutathione reductase, whose job it is to return the powerful antioxidant glutathione from its oxidized form to its reduced and functional form. Sometimes you will find that a chemical is in reduced form—but that doesn't mean it is in
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