FREE RADICALS AND ANTIOXIDANTS IN HEALTH AND DISEASE

It is ironic that oxygen, an element indispensable for life can, under certain situations, have severely deleterious effects on the human body. Most of the potentially harmful effects of oxygen are due to formation and activity of a number of chemical compounds, known as reactive oxygen species, which have a tendency to donate oxygen to other substances. Many such reactive species are free radicals and have a surplus of one or more free-floating electrons rather than having matched pairs and are, therefore, unstable and highly reactive. Types of free radicals include the hydroxyl radical (OH), the superoxide radical (O2), the nitric oxide radical (NO) and the lipid peroxyl radical (LOO). Because they have one or more unpaired electrons, free radicals are highly unstable. They scavenge your body to grab or donate electrons, thereby damaging cells, proteins, and DNA (genetic material). The same oxidative process also causes oils to become rancid, peeled apples to turn brown and iron to rust.

ANTIOXIDANTS – The wonder food                     

A single cause for ageing, heart disease, atherosclerosis, stroke and immune disorders is a villain called the free radical which is nothing but the injured oxygen atom. These free radicals react by attacking normal fatty cell membranes and producing peroxide enzymes, which damage the innerling of blood vessels by oxidizing the LDL cholesterol. This damage is manifested as atherosclerosis, diabetes, cataract and premature aging.

“Look and feel younger!” “Reverse the aging process!” “Boost your energy” What could possibly do all that? - - ANTIOXIDANTS. They are believed to play a role in preventing the development of such chronic diseases as cancer, heart diseases, stroke, Alzheimer’s disease, Rheumatoid arthritis and cataracts.

PRODUCTION OF FREE RADICALS IN THE HUMAN BODY

Free radicals and reactive oxygen species are derived either from normal essential metabolic processes in the human body or from external sources such as exposure to X Rays, ozone, cigarette smoking, air pollutants and industrial chemicals. As your body burns the carbohydrates, free radicals are produced as a by-product. Your body also gets additional free radicals from breathing polluted air, smog, vehicle exhaust and tobacco smoke, drinking alcohol and eating fatty foods. Even personal stress can produce free radicals. With electrons unhinged, free radicals roam the body, wrecking havoc. The free radical, in an effort to achieve stability, attacks nearby molecules to obtain another electron and in doing so, damages those molecules. This situation can be compared to letting a bachelor into a dance where people have come as couples. The bachelor begins cutting in, each time leaving another bachelor, so the breaking up of couples spreads through the dance floor.

If free radicals are not inactivated, their chemical reactivity can damage all cellular macromolecules including proteins, carbohydrates, lipids and nucleic acids.

Counteracting free radical damage

The human body has several mechanisms to counteract damage by free radicals and other reactive oxygen species. These act on different oxidants as well as in different cellular compartments.

One important line of defense is a system of enzymes, including glutathione peroxidases, superoxide dismutases and catalase, which decrease concentrations of the most harmful oxidants in the tissues. Several essential minerals including selenium, copper, manganese and zinc are necessary for the formation or activity of these enzymes.

The second line of defense against free radical damage is the presence of antioxidants. An antioxidant is a molecule stable enough to donate an electron to a rampaging free radical and neutralize it, thus reducing its capacity to damage. Some such antioxidants, including glutathione, ubiquinol and uric acid, are produced during normal metabolism in the body. Other lighter antioxidants are found in the diet. Although about 4000 antioxidants have been identified, the best known are vitamin E, vitamin C and the carotenoids.

ANTIOXIDANTS TO THE RESCUE! – HOW ANTIOXIDANTS MAY PREVENT AGAINST FREE RADICAL DAMAGE

As the name implies, antioxidants are substances that are capable of counteracting the damaging, but normal effects of the process of oxidation in animal tissue. Antioxidants are nutrients (vitamins and minerals) as well as enzymes (proteins in your body that assist in chemical reactions). They are thought to protect the body against destructive effects of free radicals. Antioxidants neutralize free radicals by donating one of their own electrons, ending the electron-“stealing” reaction. The antioxidant nutrients themselves don’t become free radicals by donating an electron because they are stable in either form. They act as scavengers, helping to prevent cell and tissue damage that could lead to cellular damage and disease.

Antioxidants block the process of oxidation by neutralizing free radicals. In doing so, the antioxidants themselves become oxidized. That is why there is a constant need to replenish our antioxidant resources.

How their work can be classified in one of two ways:

1.       Chain-breaking: When a free radical releases or steals an electron, a second radical is formed. This molecule then turns around and does the same thing to a third molecule, continuing to generate more unstable products. The process continues until termination occurs. i.e. either the radical is stabilized by a chain-breaking C and E, or it simply decays into a harmful product.

2.       Preventive: Antioxidant enzymes like superoxide dismutase, catalase and glutathione peroxidase prevent oxidation by reducing the rate of chain initiation. That is, by scavenging initiating radicals, such antioxidants can thwart an oxidation chain from ever setting in motion. They can also prevent oxidation by stabilizing transition metal radical such as copper and iron.

                                                               

The effectiveness of any given antioxidant in the body depends on which free radical is involved, how and where it is generated, and where the target of damage is. Thus, while in one particular system and antioxidant may protect against free radicals, in other systems it could have no effect at all. Or, in certain circumstances, an antioxidant may even act as a “pro-oxidant” that generates toxic oxygen species. Although a wide variety of antioxidants in foods contribute to disease prevention, the bulk of research has focused on three antioxidants which are essential nutrients or precursors of nutrients. These are Vitamin E, Vitamin C and the carotenoids. Each of these antioxidant nutrients have specific activities and they often work synergistically to enhance the overall antioxidant capability of the body.

 

The balance between the production of free radicals and the antioxidant defense in the body has important health implications. If there are too many free radicals produced and too few antioxidants, a condition of “oxidative stress” develops which may cause chronic damage.

 

Hope you liked this article!

 

Please note that this article is written by Dr. Bimal Chhajer (Heart Specialist in Delhi)