The Free Radical Theory of Aging


The picture above shows iron rust. Oxygen reacts with steel, in a process called oxidation. It gives a grey and red color, and soon, steel disintegrate. The process can be accelerated with air or water moisture.

Oxidation can also been seen in food, turning rancid cooking oils or transforming nice apples into sad brown food. This process of oxidation creates free radicals.

An Unifying Theory?

Free radicals are also found in polluted air and cigarette smoke. Toxins and harmful food can also create free radicals. Meanwhile, while strenuous exercise generate oxidative stress, it also reduces free radicals in our body days and weeks after the exercise.

In the 1950s, a scientist named Denham Harman conceived the free radical theory of aging. He suggests organisms age because cells accumulate free radical damage over time. Each free radical can destroy an enzyme, protein molecule or a complete cell. They can further multiply by process of a chain reaction. These reactive substances can damage cell structures so badly that immunity is impaired and DNA codes are altered. It seems free radicals age us in the same way the steel chain above slowly disintegrate into frail rust.


Aging is a complex issue. Denham Harman’s theory has evidence to back it, but has also been challenged by other scientists. I doubt we will ever fully understand the mechanism.

For me, I found this theory is a simple and easy to understand analogy how pollution, psychological stress, nutrition and exercise are tied together. The reality could be much more complex (and it should be), but it lets me grasp how our environment and what we do can shape us.

Preventing Rust

How do we avoid becoming like the wrinkling, rusted steel above?

In the theory of free radicals, it means avoiding elements bringing free radicals. This ranges from oxidized oil or meat with oxidized fat. Preservatives used in processed meats — including sausages, bacon, ham, pepperoni, salami and many deli meats — may also create free radicals. Nutrition can fortunately bring antioxidants foods such as vegetables and fruits that can help slow down the oxidative stress.

Automobile emissions, cigarette smoke, chimney emissions, and industrial gases high in heavy-metal content have particles travelling great distances. Many of the individual pollutants that make up this ambient mix are free radicals (for example, nitrogen dioxide) or have the ability to drive free radical reactions (for example, ozone and particulates). As a consequence, exposure to a wide range of air pollutants gives rise to oxidative stress within the lung. Radiation and UV light also generate free radicals.


Inversely, we can exercise. The body is slightly weakened, recovers, and becomes more resistant to oxidative stress in the future. With consistent training, the capacity of the body will expand; ultimately leading to improvements in health and human performance. Multiple studies have shown for example that after Ironman triathlons, well-trained athletes have a large decline in DNA damage for about three weeks.

Studies also found a link between oxidative stress and high anxiety and depression. While no cause-effect relationship has been proved, anxious individuals have more free radicals. Meditation, deep breathing or relaxing activities such as yoga can have a decreasing effect.

Take away

The free radical theory of aging motivates me more in exercising and making sure I have good nutrition. I think of the rusting steel chain and then remember I should avoid burnt oil, plastics and stay away from pollution. And I’m sure it also motivates you into being more aware of what you do and your environment !


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