Aging is a natural, normal part of life. We sometimes tend to fear growing older, accepting without question the belief that ill health and infirmity are inevitable consequences of the aging process. It doesn't need to be this way. While it's true that our risk of disease goes up as we age, there is no reason why we cannot enjoy good health for a lifetime. In fact, science is learning more about how we can do just that. No one can turn the clock back on aging, but an impressive body of scientific research points the way to strategies that may help people stay healthier as they grow older, and perhaps even live longer. How long you live and how healthy you remain while you live depend a great deal on the way you live.(1, 2)

The maximum possible human life span is estimated to be about 120 years.(3) The average life expectancy in developed countries is 76 to 79 years. Why the difference? While science has yet to discover how to increase the maximum potential life span, people can adopt lifestyle and nutritional strategies that may allow them to live in relatively good health significantly longer than the current average life expectancy. At center stage in aging research is a class of substances found in the human body and in nature, called "free radicals."

Free radicals: The free radical theory of aging, first presented by Denham Harman, M.D., in 1956,(4) says that changes that occur in the body with aging are caused by the buildup of free radicals. In a recently published paper, Dr. Harman discusses a growing scientific consensus that free radicals are a major cause of aging--maybe the only one.(5)

What, exactly, is a free radical? Everything that exists in the physical world around us--natural or man-made--is held together by chemical bonds. All substances are made of molecules that bond to each other by sharing electrons, the subatomic particles that orbit the atom's nucleus. Electrons like to form pairs; the pairing of electrons creates a biochemical peace and stability, without which, everything would come apart at the seams. Free radicals are molecules that have an unpaired electron. This unpaired electron makes the free radical highly unstable, like a sort of molecular loose cannon. So anxious is the free radical to find a mate for its solitary electron, it will snatch an electron away from whatever is close by. The issue is far from settled at this point, however: you may now have another equally rapacious free radical desperate to replace its stolen electron. This can set off a chain reaction producing thousands of free radicals in less than a wink of an eye.(6) The process continues until something comes along with spare electrons--a biochemical benefactor that can give up an electron without itself becoming a free radical--and order is restored.

These molecular peacekeepers, substances that donate electrons to halt free radical chain reactions, are called "antioxidants." Also known as "free radical scavengers," antioxidants include familiar nutrients like vitamins A, C, and E. The plant world fairly brims with antioxidants, which is one reason why fruits and vegetables are so healthy.

What happens if an antioxidant is not available in sufficient quantity to halt the free radical chain reaction? Our cells and tissue suffer collateral damage. Fatty molecules in cell walls, proteins, enzymes that regulate cell function, even DNA itself are all vulnerable to free radical attack.(7)

What does all this have to do with aging? Fortunately, nature has outfitted the body with a rapid-response team of enzymes that neutralize free radicals before they can do much damage. In health, and in youth, we have an abundance of these enzymes. As we age, the body may not produce enough antioxidant enzymes to ke