What does "antioxidant" mean?

As long as we, living creatures, use oxygen to live, we cannot escape the chemical reaction called "oxidation". Of course, the other side of oxidation is a chemical reaction called reduction. When oxygen oxidizes carbon, oxygen is being reduced. Oxidation and reduction are one and the same.

 

Oxidation is often referred to as "rusting the body", so people tend to think of oxidation as a bad thing, but it's not that simple.

Therefore, anti-oxidation, or "resisting oxidation", does not mean resisting oxidation (and reduction) reactions in the body. If we do that, we will die....

What we need to resist is "excessive oxidation".
Reactive oxygen species (ROS) are a typical cause of excessive oxidation.

Reactive oxygen species are also used to fight off foreign substances such as bacteria that have invaded the body, so we living creatures have an inherent mechanism to produce reactive oxygen species.

In the case of mammals, it is generally believed that several percent (many believe it to be around 2%) of the oxygen taken into the body is converted into reactive oxygen species. These can damage healthy cells as well as protect the body.
On the other hand, the body is also equipped with mechanisms to prevent its negative effects, such as losing the activity of excess reactive oxygen species and repairing damaged genes. That's why we can live without thinking "My body is rapidly rusting!". The biological body is really well-developed.

However, as we get older, this defense function also deteriorates. Stress, smoking, inactivity, radiation, and other external reasons can cause an increase in the amount of reactive oxygen species (ROS) generated, and the defense function may not be able to keep up. This is how excessive oxidation occurs.
When reactive oxygen species react with proteins, they cause denaturation, which is the loss of protein function and can lead to atherosclerosis. Also, various enzymes essential for biological reactions lose their activity. If they react with red blood cells, the red blood cells will not be able to carry oxygen. If genes are damaged faster than they can be repaired, diseases such as cancer may occur.
What we do to reduce the damage of these reactive oxygen species is what is often called "antioxidation".

In general, this means consuming foods that are rich in antioxidants. Vitamin C and vitamin E are typical examples. These substances have the property of reacting with active oxygen and detoxifying it faster than cells. As we age, the amount of antioxidants produced in our body tends to decrease, so it would be effective if you want to get antioxidant effects easily as you get older.
The other is to control the amount of excess active oxygen produced.

This is an even more effective method, but it is difficult to achieve because it involves improving one's lifestyle, such as diet and lifestyle.