“Both aging and the diseases of old age are caused essentially by slow oxygen poisoning.”
So states Nick Lane, author of OXYGEN: The Molecule That Made The World.
According to Lane, Oxygen molecules—though they are necessary for proper bodily function— are also poisonous to our cells. Lane describes how Oxygen molecules begin a series of reactions inside our cells that produce a chain of harmful Free Radicals. Free Radicals are not only individually and directly harmful to us (being highly reactive molecules that can tear apart necessary or benign molecules present in our cells), but their accumulation jars the body into a state of Oxidative Stress.
Oxidative Stress produces inflammation and other stress responses by the body, generally creating what Lane calls a “harsh environment for the expression of normal genes.” Thus, prolonged Oxidative Stress ultimately weakens the body and alters the spectrum of genes being turned on (or off) by our bodies.
There are two major theories of Aging:
1) Programmed Aging: wherein death is seen as a purposeful design of our genes, and the aging process as something as natural and necessary as the growth of an embryo or the onset of menopause.
2) Stochastic Aging: wherein aging is the accumulation of wear and tear on the body over a lifetime; much of this damage, according to Lane, comes from decades of Oxidative Stress stemming from the creation of Oxygen-generated Free Radicals made inside our Mitochondria and released into our cells; the Stochastic view of aging does NOT believe aging is inevitable.
Falling somewhere in between these two lines of thought is a theory espoused by Paul Turke which basically says that our own Immune Systems turn against us over time. Under Turke’s interpretation, our Immune System has an evolution-sanctioned “age bias”— it provides massive benefits when we are young (and have great present or future potential for producing offspring), but produces detrimental effects in our old age (when, evolutionarily speaking, the price of our stock is down).
Lane explains how the Immune System turns traitor…
One of the ways our body defends against infection is to release “noxious oxidants” in the vicinity of invading microbes, thus (hopefully) killing them. The downside is that the same noxious oxidants that are curtains for the bad guys are also not very good for our own cellular components and can produce a state of Oxidative Stress in the body (Oxidative Stress basically just means that there are alot of Free Radicals or “noxious oxidants” running around inside us and taxing our bodies’ defenses). Thus, says Lane, “Oxidative Stress is a necessary part of our response to infection.” And Lane believes that it is Oxidative Stress which causes, or at least speeds-up, aging.
Another way in which Free Radicals and Oxidative Stress play into aging is via what has been called the “Rate Of Living” theory. Under this theory, an organism’s rate of Metabolism is directly tied to to the length of the life-span, with faster metabolisms (relative to body weight) resulting in shorter lives. Lane believes this connection between metabolism and life-span is a direct consequence of the fact that the faster we metabolize Oxygen, the faster we produce Free Radicals. You might also call this theory the Live Fast And Die Young theory.
As support for the Rate Of Living theory of aging, Lane cites the natural world around us: typically, smaller animals have faster metabolic rates (something to do with the effort it takes for a tiny body to maintain its body temperature in the great big world). Also typically, smaller animals have shorter life-spans. Using this simple relationship, scientists have found a formula that demonstrates the correlation between metabolic rate and life-span:
Metabolic Rate * Lifespan = the “Life-Time Energy Potential.”
The Life-Time Energy Potential is a constant that holds-up pretty well across the different species of mammals. It works-out to equal the processing of about 60,000 liters of Oxygen per Kilogram Of Body Weight over a life-time. This constant holds true for everything from a mouse to a horse (exceptions granted). Run through your 60,000 liters-per, and the party’s over.
Yet another way that Lane supports his theory that Oxygen is slowly killing us is the discovery, decades ago, that strict caloric restriction (putting an organism on a starvation-approaching diet) actually prolongs life, something which may seem counter-intuitive to some of us. Lane believes the increase in life-span due to caloric restriction is due to the resultant drop in blood Glucose levels which in turn lowers Insulin levels; then, when the body senses less Insulin in the body, it realizes that the system is suffering under nutritional duress and shifts resources toward bodily maintenance, which includes providing greater resistance to Oxidative Stress. For Lane, it is this increased fire-power against Oxidative Stress that produces the longer life-spans.
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