Understanding free radicals

Taiwanese surgeon Dr. Ko Wen-je once said that there would be only two choices by the end of our lives: with or without intubation. Although Taiwanese people live a long life, many of them spent their declining years in sickness and pain. Statistic shows that among the top ten causes of death in Taiwan, most of them are diseases related to free radicals. Scientists have proven that there are at least over 100 types of diseases that are free radicals-related.What are free radicals?Free radicals are dynamic, unstable compounds with a short life cycle. Their instability causes them to produce a chemical reaction with the cell tissues in our body. This chemical reaction, known as oxidation, will cause abnormal function of cell tissues, and it can even lead to DNA damage, cell damage and mutation and cause cancer. Nonetheless, free radicals have their benefits. When the body is invaded by bacteria, mould, virus or foreign matters, the body defence system will inform phagocytes to be on standby. Phagocytes will be catalysed by related enzymes and release superoxide radicals to clear the bacteria or infected cells. In other words, the body needs to have an appropriate amount of free radicals to prevent and fight off diseases. Unfortunately, free radicals are not able to tell the good ones from the bad. When the free radicals in our body are out of balance, they will become a threat to normal cells.

How are free radicals formed? So, where does this troublesome substance come from? It comes from two sources:
1. it is created through normal physiological functions within the human body
2. It is created by adverse external and environmental factors.

Human physiological functions:
1. Metabolism: The body’s normal metabolism itself is an oxidation process, and free radicals are the by-products of metabolism. The body will produce many useful chemical substances to maintain normal operation of the human body which will generate free radicals too.
2. Defence against bacteria: When virus and bacteria enter the body, white blood cells will use free radicals to engulf these foreign invaders. Thus, whenever there is inflammation in the body, it will generate a large number of free radicals.

External and environmental factors:Environmental factors are also the source of free radicals, or forcing the body to produce more free radicals, posting a threat to human health.

1. Smoking (secondhand smoke), excessive drinking (A cigarette can produce up to 10,000,000,000,000,000 free radicals!)
2. Radiation, UV rays, electromagnetic waves, sun exposure, radiotherapy received by cancer patients, pesticides
3. Environmental pollution: including air pollution, drinking water pollution, industrial waste water pollution, soil pollution.
4. Chemical drug abuse: food additives, pesticides, contaminated fruits and vegetables, drugs and drug abuse.
5. Mental condition: Over-stressed, irritability, anxiety, depression, nervousness. When the number of free radicals in the body exceeds the normal scope of defence, it will lead to a “free radical chain reaction”, causing the basic substances that make up a cell, including protein, carbohydrates and lipid being oxidised and turned into free radicals, and end up triggering other oxidation processes. The vicious cycle gradually weakens and damages the body functions, followed by various diseases.

A normal chemical substance is made up of atoms and molecules, with pairs of electrons to maintain stability. On the other hand, free radicals are atoms or molecules with unpaired electrons, forcing it to steal electrons from other atoms or molecules to make a match to overcome its instability. However, if the free radicals are stealing electrons from proteins, carbohydrates and lipids, these oxidised substances will end up stealing electrons from other atoms or molecules. Eventually, the body’s cell membranes, proteins and nucleic acids will become oxidised, bringing adverse effects to most body organs and systems.

With the overwhelming free radicals in the body, they will ‘turn bad’ and wreak havoc in the body:
1. Damages DNA.
2. Destruction of unsaturated fats that leads to lipid peroxidation.
3. Destructs protein molecules, oxidises body enzymes and disrupts enzyme activity.
4. Stimulates abnormal reactions of monocular leucocytes and macrophages, causing them to release inflammatory precursors which leads to inflammatory reactions.
5. Attacks the periodontal tissue, breaks down osteoclast and the bone matrix of bone interface.
6. Causes cell deterioration and death, which leads to signs of ageing.
7. Directly impacts the nucleus, causing gene mutation and cancer.
8. Damages organs like heart and blood vessels

Nonetheless, free radicals are beneficial as well. They will protect the body whenever there are invaders. For instance, superoxide radical (O2·-) is regarded as the fungicide in our body tissues. When periodontal tissue is invaded by bacteria, the immune system will inform phagocytes (including polymorphnuclear leucocyte, macrophages, eosinophil leucocytes and lymphocytes) to be ready to fight. Phagocytes will be catalysed by related enzymes to produce superoxide radicals to remove bacteria and infected cells. Superoxide radicals are able to prevent and fight against diseases.Therefore, the key to maintaining a healthy body is to achieve a balance between free radicals produced in the body and the body antioxidant defence system.Reference:  PhilCheung, Center for the Advancement of Science Education, Chang Gung Biotechnology

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