human chromosome

The Free-Radical Theory vs. Other Theories of Aging

Age-related diseases are a major concern of patients and doctors alike. The average lifespan of Americans has only increased about 15 percent since Watson and Crick first discovered the structure of DNA in 1953, and the rate of increase has actually slowed since the 1950s.

This is largely due to the fact that doctors generally tend to focus more on diseases than their prevention than the aging itself. Maintaining overall health is crucial to extending lifespan and avoiding harmful age-related diseases. Healthy lifestyle, diet, exercise and positive mental state are all factors in overall optimal health.

There are multiple theories as to what causes aging, and most nutritional biologists admit that the aging process is too complicated to be completely described by just one theory. In other words, aging rates vary based on a combination of factors.

Some of the most well-known and well-researched theories of aging are the reproductive-cell cycle theory, the cellular senescence theory, wear and tear theory, the rate of living theory and the free-radical theory.

Reproductive Cell Theory

The reproductive-cell cycle theory argues that aging is due to the changes in cells that take place throughout their cycles caused largely by hormones of the hypothalamic-pituitary-gonadal axis (HPG axis).

Men begin to show these hormonal changes on the cellular level in their thirties and women (who live longer) do not show these hormonal changes to a large degree until after they have reached menopause which happens around the age of 50.

Cellular Senescence (aka Telomere Theory)

The cellular senescence (also known as the telomere theory) postulates that aging happens on the cellular level as telomeres are shortened through cellular divisions. The aging process becomes visible over time and continues until the cells eventually die or mutate into cancer cells.

Telomeres are the protective bundles at the ends of chromatids, which protect genetic information during cellular division. Without telomeres cells would disintegrate or fuse together. Proponents of this theory believe that healthy living and certain supplements can slow the aging process.

aging-theory-wear-tearThe Wear and Tear Theory

The wear and tear theory of aging proposes that humans and plants age by the same mechanisms that can cause any physical objects – such as machines or paint – to deteriorate. It basically hypothesizes that aging is systematic and happens after years of living, just as a car may begin to fail after years of use. This theory has some major flaws, since the lifespan of each individual within a species varies greatly from other individuals in the same species.

Rate of Living Theory

The rate of living theory of aging was one of the first theories of aging ever thoroughly documented. It was first proposed by Raymond Pearl in 1928 who stated that aging was caused by an overall fast basal metabolic rate.

High metabolism is supposed (within the definitions of this theory) to cause chemical damage to long-lived biopolymers such as proteins and DNA. This theory has not ever been fully supported within in the biological sciences, since it is difficult to pinpoint any differences based on rates of metabolism even between species, let alone between members of the same species.

The Free-Radical Theory and its Variations

The free-radical theory of aging was first proposed by Dehman Harman in the 1950s. Harman’s theory, which now has various modifications, holds more weight than the rate of living theory or the wear and tear theory. Possibly combined with the reproductive-cell cycle theory or the cellular senescence theory, a general understanding of why aging occurs can begin to emerge.

Free radicals
Free radicals

The free-radical theory of aging states that aging is due to damage on the cells caused by free radicals, which are byproducts of oxidation. A free radical is an atom or molecule that has a single unpaired electron in its outer shell. Most free radicals are highly reactive and are well-documented to cause large amounts of oxidative stress on the body.

One modification of Harman’s theory is the mitochondrial free-radical theory of aging, which hypothesizes that mutated mtDNA causes more oxidative stress on the body and thus more apparent aging due to free radicals. The epigenetic oxidative redox shift theory modification integrates with Harman’s original free-radical theory of aging, but places an emphasis on the role of insulin in aging and argues that a sedentary lifestyle leads to more rapid aging rates.

Luckily, free radicals are not indestructible molecules. They can be combated and stabilized using a variety of antioxidants. Some people take antioxidant supplements, but it is also effective to consume a wide variety of colorful fruits and vegetables, leafy greens, citrus, cocoa, teas, nuts, seeds, and berries; and to monitor ORAC values to determine the best course of action to combat free radicals in the body.