Free radicals: definition, causes, antioxidants and cancer


Free radicals are highly reactive and unstable molecules that occur naturally in the body as a by-product of metabolism (oxidation) or when exposed to environmental toxins such as tobacco smoke and ultraviolet light. Free radicals have a lifespan of just a fraction of a second, but during this time they can damage DNA, sometimes leading to mutations that can lead to cancer. Antioxidants in the food we eat can neutralize unstable molecules, reducing the risk of harm.

Peter Close / / File Photo

We take a look at the structure, causes, and effects of free radicals, and what you should know about antioxidant supplements if you have cancer.

Definition and structure of free radicals

Free radicals are atoms that contain an unpaired electron. Due to the lack of a stable number of electrons in the outer shell, they are constantly searching for a bond with another electron to stabilize themselves, a process that can damage DNA and other parts of human cells. This damage can play a role in the development of cancer and other diseases and accelerate the aging process.

Types of free radicals

There are many types of free radicals, but for humans the most important are free radicals (reactive oxygen species). Examples include singlet oxygen (when oxygen is "split" into individual atoms with unpaired electrons), hydrogen peroxide, superoxides, and hydroxyl anions.

Causes / sources of free radicals

You may be wondering where free radicals come from. Free radicals can be obtained in several ways. They can be formed as a result of normal metabolic processes in the body or as a result of exposure to carcinogens (cancer-causing substances) in the environment.

Free radicals can be produced by both carcinogens and normal metabolic processes in cells.

Free radicals caused by normal metabolic processes.

Our bodies often produce free radicals during the breakdown of nutrients to create the energy that allows our bodies to function. The production of free radicals in normal metabolic processes like this is one reason why cancer risk increases with age, even when people are less exposed to carcinogens.

Free radicals due to exposure to carcinogens.

Exposure to carcinogens in the environment can also produce free radicals. Examples of some carcinogens:

  • Tobacco smoke
  • Ultraviolet radiation
  • Radon in the house
  • Environmental and occupational chemicals and substances such as asbestos and vinyl chloride
  • Some viruses
  • Medical radiation
  • The air pollution

Effects of free radicals in the body: oxidative stress

Once free radicals are formed as a result of exposure to carcinogens or during normal metabolic processes in the body, they can cause damage. The presence of free radicals creates what is called oxidative stress in the body. The reason this is called oxidative stress is because the reactions that take place, which give free radicals an electron, take place in the presence of oxygen.

In fact, the process is much more complicated and, in fact, it is a vicious cycle. When a free radical "steals" an electron from a molecule, that molecule loses an electron (becomes a free radical), and so on. Free radicals can damage not only DNA (nucleic acids), but also proteins, lipids, cell membranes, and much more in the body. Damage to proteins (protein cross-linking, etc.) and other components of the body can directly cause disease.

Free radicals and aging

There are several theories to explain why our body ages and free radicals are included in one of these theories. However, not only are free radicals responsible for the changes associated with aging, normal aging is likely associated with several different processes in the body.

How Free Radicals Can Cause Cancer

Damage to genes in DNA can lead to the formation of genes that produce ineffective proteins; Proteins were supposed to watch over the cells of the body. Some of these mutations may include genes known as tumor suppressor genes . These genes encode proteins that work to repair DNA damage or cause cells that cannot be rescued to be killed during apoptosis (programmed cell death).

Oncogenes are genes that encode proteins that promote cell growth. The body's normal genes, called "proto-oncogenes," are important for stimulating the baby's growth during pregnancy and temporarily produce proteins that help with tissue repair. Mutations in these genes (which later become oncogenes) lead to the continuous production of proteins that promote cell growth.

Most often, cancer is caused by a series of mutations in tumor suppressor genes and oncogenes. Damage (mutations) of tumor suppressor genes allows the damaged cell to survive without repair (abnormally) and damaged oncogenes promote the growth of this damaged cell. The result is the formation of a cancer cell .

Antioxidants and free radicals.

Many phytochemicals (plant chemicals) in the food we eat act as antioxidants. These nutrients work by suppressing the formation of free radicals and can reduce the damage they can cause to the body. This is believed to be at least one of the reasons that a diet rich in vegetables and fruits is associated with a lower risk of many diseases.

Examples of antioxidants include vitamin E, vitamin A, beta-carotene, anthocyanidins (in berries), epigallacatechin-3-gallate (EGCG) in green tea, and many others.

Antioxidant supplements

Many studies have shown that eating foods rich in antioxidants is associated with a lower risk of diseases, including cancer. Unfortunately, simply supplementing your diet with antioxidant supplements doesn't seem to have the same effect.

An example is lung cancer . Knowing that people who ate more foods rich in beta-carotene and vitamin E had a lower risk of lung cancer, the researchers conducted a study in which one group of people took a daily beta-carotene supplement and the other did not. … Men who smoked and took beta-carotene actually had a higher risk of developing lung cancer .

Antioxidants in people who already have cancer.

It is very important that those undergoing cancer treatment discuss any antioxidant supplement, or any supplement for that matter, with their oncologist. Several different concerns have been raised.

One refers to people receiving cancer treatments, such as chemotherapy and radiation therapy. Some vitamin supplements can reduce the effectiveness of cancer treatments, and the reason for this becomes clear when the mechanism of these treatments is considered. Some cancer treatments, such as radiation, create free radicals to destroy cancer cells. In such conditions, the use of antioxidants could theoretically reduce the effectiveness of the treatment. In this case, antioxidants can help protect the cancer cells you are trying to destroy.

(While antioxidant supplements are often discouraged for this reason, most oncologists believe that eating a healthy diet that contains foods rich in antioxidants is not a problem.) Several different studies published in 2019 support this concern.

In one study, postmenopausal women with breast cancer who used antioxidant supplements during chemotherapy and radiation therapy found a worse prognosis. In two separate studies, cell studies show that antioxidant supplements (such as vitamin E) can promote the growth and spread of lung cancer .

Taking antioxidant supplements (not diet) can worsen the prognosis for a person with certain types of cancer.

Antioxidants, free radicals, and cancer

Cancer is usually caused by a series of mutations that cause uncontrolled growth and relative immortality of the cell. Since the fruits and vegetables in our diet are rich in antioxidants, it is believed that this may be one of the reasons why a diet rich in fruits and vegetables is consistently associated with a lower risk of cancer.

However, as noted above, supplementation with these antioxidants has not been effective and most oncologists recommend dietary sources of these nutrients. Also, certain vitamin and mineral supplements can interfere with cancer treatment .

How to reduce the amount of free radicals in your body

Reducing the amount of free radicals in your body includes both reducing the likelihood of free radical formation and providing your body with antioxidants. The body produces antioxidants on its own, but not only in sufficient quantities. However, it is important to note that because free radicals are produced during normal cellular processes, people can "get it right" and still develop cancer.

Reducing your exposure to free radicals includes both eliminating their sources (carcinogens) and providing your body with beneficial antioxidants in your diet.

Lifestyle measures to reduce exposure include quitting smoking, avoiding processed foods, being careful around chemicals you work with at home or work, and more.

When it comes to getting a healthy variety of antioxidants in your diet, nutritionists often recommend eating " rainbow foods " with foods of different colors, which often contain different kinds of antioxidants.

Get the word of drug information

It is impossible to completely eliminate the effects of free radicals, especially those that are formed as a result of normal metabolism in the body. However, switching to a healthy diet rich in a variety of antioxidants is a great start.

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