By Richard Harkness
Knight Ridder News Service

I hear about free radicals and the damage they do to the body, but it escapes me exactly what they are. Could you explain in simple terms, including how antioxidants fight free radicals?

Consider this column Free Radicals 101.

A little background in chemistry will help.

Atoms such as carbon, hydrogen and oxygen carry electrons that reside in "shells" surrounding the atom's nucleus.

Most atoms in their normal state fall short of a full allotment of electrons in their outer shell. Atoms seek to fill this shell because that makes them stable.

To gain the needed electrons, atoms can bond with other atoms to form molecules, each atom using the shared electrons as its own.

(Water is a molecule consisting of 1 oxygen atom and 2 hydrogen atoms.)

A free radical is a molecule containing an atom that is short an electron in its outer shell, and this makes it highly reactive. Examples are the hydroxyl radical and the superoxide anion.

These free radicals - sometimes called reactive oxygen species - quickly attack other molecules and steal their electrons.

Such plundered molecules are said to be oxidized. Oxidation is the loss of electrons. It's the same process that causes metal to rust.

This is where antioxidants such as vitamin E come in. They neutralize free radicals by donating their electrons to them. In this way, antioxidants spare important molecules from oxidative damage.

Free radicals can do a lot of damage quickly by starting a chain reaction. As free radicals loot electrons from target molecules, the molecules themselves become free radicals, in turn lifting electrons from other molecules.

This domino effect can continue until free radicals happen to meet and neutralize each other by sharing their own electrons.

The damage to cells caused by free radicals is thought to play a role in the development of cancer, heart disease and many other aspects of aging.

Free radicals are produced in the body during normal cell metabolism, from tissue injury and as a result of exposure to tobacco smoke, sunlight, X-rays and other environmental sources.

Ordinarily, the body's natural antioxidants neutralize free radicals. In some cases, though, free radicals ravage out of control and deplete the body's store of antioxidants.

Free radicals also come in handy, so you don't want to completely stamp them out. For example, they're important in making thyroid hormone and in helping white blood cells fend off disease-causing bacteria.

Problems occur when the production of free radicals overwhelms the body's ability to contain them. Balance seems to be the key. It's generally believed that a proper balance between free radicals and antioxidants is essential to good health.

Antioxidants are found in an array of nutrients and foods, including vitamins A, C and E, as well as beta carotene, lutein, selenium, grapeseed, lipoic acid, resveratrol (from red wine), soy isoflavones, CoQ10, garlic and fruits and vegetables.

E-mail: rharkn@aol.com