Theories of aging

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WE ARE FOREVER IN SEARCH OF THE CURE FOR OLD AGE. Dozens of theories have been proposed, yet science has not produced a universal theory of aging. Generally scientists believe that aging is a mechanism installed in the human body to insure the continued survival of the species. From the species' point of view, the most important time of our lives is our period of fertility, the years during which we are able to create new life.

As a result, many bodily functions begin to decline, with ever accelerated losses of function continuing in each succeeding decade.

Why do we age? Current theories of aging at the cellular and molecular level generally revolve around two themes: aging is programmed and aging is accidental. Programmed aging theories are based on the idea that from conception to death, human development is governed by a biological "clock." This clock sets the appropriate times for various changes to take place. The changes in vision, loss of calcium in the bones, decreasing hearing acuity and lowered vital capacity of the lungs are all examples of programmed aging. Accidental theories of aging rely on chance-the notion that organisms get older by a series of random events. Examples are DNA damage from free radicals or just the wear and tear of daily life.

Here are the four principal theories of aging, each of which accounts for some aspects of the process.

1) "WEAR AND TEAR" THEORY
Dr. August Weismann, a German biologist, first introduced this theory in 1882. He believed that the body and its cells were damaged by overuse and abuse. The organs-liver, stomach, kidneys, skin and so on are worn down by toxins in our diet and in the environment; by the excess consumption of fat, sugar, caffeine, alcohol and nicotine; by the ultraviolet rays of the sun and by the many other physical and emotional stresses to which we subject our bodies. Wear and tear is not confined to our organs, however it also takes place on the cellular level.

Of course, even if you've never touched a cigarette or had a glass of wine, stayed out of the sun and eaten only natural foods, simply using the organs with which nature endowed you is going to wear them out. Abuse will only wear them out more quickly. Likewise, as the body ages, our very cells feel the effect, no matter how healthy our life style.

When we're young, the body's own maintenance and repair systems keep compensating for the effects of both normal and excessive wear and tear. With age, the body loses its ability to repair damage-whether caused by diet, environmental toxins, bacteria or a virus. Thus, many elderly people die of diseases that they could have resisted when they were younger.

By the same token, nutritional supplements and other treatments can help reverse the aging process by stimulating the body's own ability to repair and maintain its organs and cells.

2) NEUROENDOCRINE THEORY
This theory, developed by Vladimir Dilman, Ph.D., elaborates on the wear-and-tear theory by focusing on the neuroendocrine system, the complicated network of biochemicals that govern the release of our hormones and other vital bodily elements. When we're young, our hormones work together to regulate many bodily functions, including our responses to heat and cold, our experiences and sexual activity. Different organs release various hormones all under the governance of the hypothalamus, a walnut-sized gland located within the brain.

The hypothalamus sets off various chain reactions, in which an organ releases a hormone which in turn stimulates the release of another hormone, which in turn stimulates yet another bodily response. The hypothalamus responds to the body's hormone levels as its guide for how to regulate hormonal activity.

When we're young, hormone levels tend to be high, accounting for, among other things, menstruation in women and high libido in both sexes. As we age, though, the body produces lower levels of hormones, which can have disastrous effects on our functioning. The growth hormones that help us form muscle mass, hGH, testosterone and thyroid, for example, drop dramatically as we age, so that even if an elderly person has not gained weight, he or she has undoubtedly increased the ratio of fat to muscle.

Hormones are vital for repairing and regulating our bodily functions and when aging causes a drop in hormone production, it causes a decline in our body's ability to repair and regulate itself as well. Moreover, hormone production is highly interactive: the drop in production of any one hormone is likely to have a feedback effect on the whole mechanism, signaling some organs to release lower levels of other hormones which will cause other body parts to release lower levels of yet different hormones.

Thus, hormone replacement therapy, a frequent component of any anti-aging treatment, helps to reset the body's hormonal clock and so can reverse or delay the effects of aging. If our hormones are being produced at youthful levels, in a very real sense the cells of our bodies are stimulated to be metabolically active and thus we stay young.

3) GENETIC CONTROL THEORY
This planned-obsolescence theory focuses on the genetic programming encoded within our DNA. We are born with a unique genetic code, a predetermined tendency to certain types of physical and mental functioning, and that genetic inheritance determines how quickly we age and how long we live.

However, as with all aspects of our genetic inheritance, the timing on this genetic clock is subject to enormous variation, depending on what happens to us as we grow up and on how we actually live (the old "nature versus nurture" debate).

Anti-aging medicine addresses this issue by augmenting the basic building blocks of DNA within each of our cells, preventing damage to and increasing repair of DNA. In this way, we believe anti aging treatment can help US escape our genetic destinies, at least to some extent.

4) THE FREE-RADICAL THEORY
This exciting development in anti-aging research was developed by Dr. Denham Harman of the University of Nebraska College of Medicine. "Free radical" is a term used to describe any molecule that differs from conventional molecules in that it possesses a free electron, a property that makes it react with other molecules in highly volatile and destructive ways.

In a conventional molecule, the electrical charge is balanced. Electrons come in pairs, so that their electrical energies cancel each other out. Atoms that are missing electrons combine with atoms that have extra electrons and neutral electrical charge.

The free radical, on the other hand, has an extra electron creating an extra negative charge. This unbalanced electrical energy makes the free radical tend to attach itself to other molecules as it tries to steal a matching electron and attain electrical equilibrium. Some scientists speak of these free radicals as "promiscuous," breaking up the happy marriage of paired electrons in neighboring molecules.

Of course, free radical activity within the body is not only or even primarily negative. Without free radical activity, that is without biochemical electricity, we would not be able to produce energy, maintain immunity, transmit nerve impulses, synthesize hormones or even contract our muscles. The body's electricity enables us to perform these functions, and that electricity comes from the unbalanced electron activity of free radicals.

But free radicals also attack the structure of our cell membranes, creating metabolic waste products including substances known as lipofuscins. An excess of lipofuscins in the body is shown as a darkening of the skin in certain areas, so-called "aging spots" that indicate an excess of metabolic waste resulting from cellular destruction. Lipofuscins in turn interfere with our cells' ability to repair and reproduce themselves. They disturb DNA and RNA synthesis, interfere with synthesis of protein (thus lowering our energy levels and preventing the body from building muscle mass) and destroy cellular enzymes, which are needed for vital chemical processes.

With age, however, the accumulated effects of free radical damage begin to take their toll. Free radical disruption of cell metabolism is part of what ages our cells. It may also create mutant cells, leading ultimately to cancer and death.

Moreover, free radicals attack collagen and elastin, the substances that keep our skin moist, smooth, flexible and elastic. These vital tissues fray and break under the assaults of free radicals, a process particularly noticeable in the face, where folds of skin and deep-cut wrinkles are testaments to the long-term effect of free radical attacks.

Because forms of oxygen itself are free radicals, our very breathing and our otherwise healthy aerobic exercise generate free radicals that help along the aging process. Hence, substances that prevent the harmful effects of oxidation are know as antioxidants. Natural antioxidants include vitamin C, vitamin E and beta carotene.

Another substance that combats free radical damage is known as a free radical scavenger, which actually seek free radicals and harmlessly bind them before they can attach themselves to other molecules and/or cause cross-linking. Many vitamins, minerals and other substances fight aging by acting as free radical scavengers.

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by Dr. Robert Goldman, President, National Academy of Sports Medicine

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