The Antioxidants - Free-Radical Fighters

The free-radical defenses, the antioxidants continually protect us from the destructive actions of free radicals. Let's focus on the four antioxidant nutrients (beta carotene, vitamin C, vitamin E, and selenium) that are the most promising for medical therapy.

The term "antioxidants" sounds complicated, but is actually easy to understand. "Anti" means "against," and "oxidants" are reactive substances that take electrons from other substances, that is, free radicals.

"Oxidant" comes from the word "oxygen." Leave oils and meats outside too long and they become rancid. Rancidity involves oxidants in a process called oxidation, which is the reaction of oxygen with fatty acids and proteins to form free radicals, eventually causing spoilage. Rusting is another example of oxidation; oxygen reacts with iron to form a weak, flaky substance, ferrous oxide, or rust. So, oxidation, rancidity, spoilage, and burning describe the same thing: free-radical destruction. In fact, knowledge of free radicals began in the 1930s when Leonor Micaelis, chemist at the Rockefeller Institute, puzzled over the reason why oils turn rancid. His discoveries were provocative at the time and spurred tremendous interest in the roles free radicals play in life.

Thus, an antioxidant fights damaging oxidation by neutralizing the free radicals which cause it. A free radical has an unpaired electron. An antioxidant can supply the missing electron or remove an extra one to stabilize the free radical. The antioxidant then technically becomes a free radical, but thanks to its structure, it is many times less reactive than the original free radical and will not damage other molecules. In terms of free radicals, the buck stops with antioxidants. Further biochemical processes complete the antioxidant process, and a free radical is safely extinguished.

The analogy of the nail on the freeway can also help illustrate how antioxidants function. If a highway sweeper had swept the nail off the road before a car could run over it, then much damage would have been avoided. Or, if the cars had tires protected with impenetrable coatings, then the nail would not be able to puncture them. Antioxidants therefore function as highway sweepers and tire sealants, averting potential devastation.

In the body, many kinds of antioxidants protect us, including enzymes, nutrients, amino acids, proteins, and other biochemicals.

Antioxidant enzymes

The antioxidant enzymes are synthesized in the body. They initiate processes which ultimately channel the excessive, damaging energies of free radicals into producing harmless substances such as water and ordinary oxygen. These enzymes include.

• glutathione peroxidase
• catalase
• superoxide dismutase

They are produced and function in most cells of the body. In every sense, they are a part of us. Without their protective activity, we would quickly become, quite literally, spoiled. In fact, the reason why dead flesh rots so quickly is that these enzymes no longer function.

The body usually reacts to the presence of increased free radicals by increasing antioxidant enzyme production. For instance, trained athletes usually have higher levels of antioxidant enzymes than most people. Their bodies have adjusted to deal with the extra free radicals from the increased metabolism of strenuous exercise. However, the stress of the modern lifestyle and the toxic by-products of technology have increased the free radical load we all must deal with. Air pollution, industrial waste, pesticide and herbicide residues, and many other sources produce free radicals that did not plague previous generations. Thus, the ability of our bodies to produce sufficient antioxidant enzymes may be stressed and may become insufficient.

Other antioxidants

Other classes of antioxidant substances exist. Synthetic antioxidants such as dimethyl sulfoxide (DMSO), butylated hydroxyanisole (BRA), and butylated hydroxytoluene (BHT) are used as pharmaceutical agents and food preservatives. Other natural antioxidants include sulfur-containing amino acids and proteins (e.g., cysteine and glutathione), uric acid, and numerous substances derived from herbs.

Antioxidant nutrients

For human supplementation, most clinical researchers use antioxidant nutrients, because these are the most practical and cost-effective choices. The antioxidant nutrients most capable of fighting free radicals include:

• beta carotene (provitamin A)
• vitamin C
• vitamin E
• and the mineral selenium

Unlike the enzymes, antioxidant nutrients are not made in the body but are richly supplied in such foods as fruits, vegetables, whole grains, nuts, and seeds. After being absorbed during digestion, they travel in the bloodstream and localize in all the cells and organs to neutralize free radicals. In the process of quenching free radicals, antioxidant nutrients are inactivated, though some may be reactivated, and are eventually eliminated from the body. Thus, they need to be constantly replenished through the diet, just as calories are constantly needed to sustain energy.

The antioxidant nutrients function together as a team to quench free radicals, often in conjunction with other classes of antioxidants, such as the enzymes. One antioxidant does not function in isolation, but each is a part of intricate biochemical chains, like bucket brigades set up to put out fires caused by free radicals. At the same time, each is distinct in chemical structure and nature, and functions in many specialized roles other than that of being an antioxidant.

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