The Free Radical Theory Overview
"The perpetual but futile struggle of individual cells to stay alive and function
normally, in the face of chemical disintegration - is the genesis of aging and all its
consequences...Indeed, the free radical theory of aging is so big it encompasses virtually
every disease you can think of that comes with increasing age. That, then, makes aging the
primary and only disease most of us ever have to worry about. As Dr. Harman notes, we have
pressed the life span about as far as it will go without attacking aging at its origin...
Degenerative diseases such as cancer, Lou Gehrig's disease and Alzheimer's are not separate
and distinguishable entities. They are merely different forms of expression, influenced by
genetics and environment, of the free radical aging process that has caught up with us. "
- Jean Carper (excerpted from Stop Aging Now!, published in 1995 by HarperCollins)
Free Radicals Act Like Rust In Your Body
The free radical theory of aging is that organisms age because cells accumulate free
radical damage with the passage of time. In general, a "free radical" is any molecule
that has a single unpaired electron in an outer shell. For most biological structures,
free radical damage is closely associated with oxidation damage. Most people can
understand oxidation damage as they are familiar with the process of rust formation.
As the name suggests, antioxidants, like vitamin C, prevent oxidation.
A nutrient's ORAC Score
is a method for determining its total antioxidant capacity and thus its ability to prevent oxidation.
In biochemistry, the free radicals of interest are often referred to as reactive oxygen
species (ROS) because the most biologically significant free radicals are oxygen-centered.
But not all free radicals are ROS and not all ROS are free radicals. For example, the free
radicals superoxide and hydroxyl radical are ROS, but the ROS hydrogen peroxide (H2O2) is
not a free radical species, however the term "free radical theory of aging" usually refers
to these compounds as well.
Free Radical Pioneer
The free radical theory of aging was conceived by Denham Harman at a time when
most scientists still believed that free radicals were too unstable to exist in
biological systems and before anybody had invoked them as a cause of degenerative
diseases. Harman drew inspiration from two sources: 1) the rate of living theory,
which held that lifespan was an inverse function of metabolic rate, oxygen
consumption. 2) Rebbeca Gershman's observation that hyperbaric oxygen toxicity
and radiation toxicity could be explained by the same underlying phenomenon:
oxygen free radicals. Noting that radiation causes "mutation, cancer and aging"
Harman argued that oxygen free radicals produced during normal respiration would
cause cumulative damage which would eventually lead to organismal loss of
functionality, and ultimately, death. In later years, the free radical theory
was expanded to not only include aging per se, but also age related diseases.
Free radical damage within cells has been linked to a range of disorders
including cancer, arthritis, atherosclerosis, Alzheimer's disease, and diabetes.
This involvement is not at all surprising as free radical chemistry is an
important aspect of phagocytosis, inflammation, and apoptosis. Cell suicide, or
apoptosis, is the body's way of controlling cell death and involves free radicals
and redox signalling. Redox factors play an even greater part in other forms of
cell death such as necrosis or autoschizis.
More recently, the relationship between disease and free radicals has
led to the formulation of a greater generalization about the relationship between
aging and free radicals. In its strong form, the hypothesis states that aging
per se is a free radical process. The "weak" hypothesis holds that the
degenerative diseases associated with aging generally involve free radical
processes and that, cumulatively, these make you age. The latter is generally
accepted, but the "strong" hypothesis awaits further proof. Both models trace
back to Dr. Harman's work.