The possible role of antioxidants in the prevention and treatment of a variety of medical conditions has been very highly publicized. For some diseases, anti-oxidants may well play an important role. Unfortunately, some of the excitement is not based on scientific evidence. In order to understand how antioxidants work, it is first important to understand the process of oxidation.

What is Oxidation?
Oxidation is a chemical process. Oxidation is the reason that metals rust and apples turn brown. When this same process happens inside your body, it can harm cells and tissues. Free radicals are small chemicals that are responsible for oxidative damage. Free radicals can be contained in (or caused to form by) a variety of things including tobacco smoke, radiation (like sunlight or x-rays) and even the normal functioning of the human body. Free radicals are unstable and they can interact with, and alter, other molecules. Targets of free radicals include DNA, lipids and proteins. When free radicals interact with other molecules, they can cause changes (called oxidation) that interfere with the normal activity of the altered target molecules. The altered activity of the affected cell parts can cause severe problems for the cell and ultimately the entire body. You can learn more about oxidation in the Closer Look on this page.

What are Antioxidants?
Antioxidants are molecules that, as the name suggests, prevent or reverse oxidation. Examples of dietary antioxidants include vitamins C and E. Antioxidants are able to interact with and neutralize free radicals in vitro ⁽¹⁾ ⁽²⁾, improve health and prolong life in animals ⁽³⁾ ⁽⁴⁾, and many studies are underway to investigate the potential of these compounds to prevent cancer in humans. Antioxidants are important to humans because they stop 'radicalized' molecules before they cause damage. Compounds that exhibit antioxidant properties do this by donating an electron to a free radical without needing to steal another electron. Unlike most compounds, antioxidants are stable with or without the electron they donate. Some antioxidants function in a "suicidal" manner, neutralizing free radicals by forming permanent bonds with them.

Sources and Uses of Antioxidants
There are many good sources of antioxidants including green tea, berries, tomatoes and soy. Antioxidants can be found in many fruits and vegetables because plants produce antioxidants to help protect themselves from free radicals created by radiation from the sun. The body naturally produces some antioxidants that help protect against free radical damage. Unfortunately, these do not provide complete protection. Humans must consume antioxidants from other sources if they wish to decrease their risk of developing diseases that are increased by free radical damage ⁽⁵⁾. Outside of the body, antioxidants can also be used for many practical purposes: museum curators use them to preserve artifacts derived from living things, they can prevent food from spoiling. They are also used to make better rubbers, plastics, automobile fuels and paint ⁽⁵⁾.

NOTE: Just because something is healthy does not mean more is better. Even the healthiest substances can cause harm if taken in large amounts.

Watch an interview about antioxidants with urologist Dr. John Petros. Choose the interview from the list.

A Closer Look at Free Radicals

Atoms are composed of a nucleus, containing particles called protons and neutrons, and a group of particles (electrons) that constantly circle the nucleus like satellites around the earth. In most molecules electrons travel in pairs around the nucleus.

Free radicals are an exception. At least one atom in a free radical has a single (unpaired) electron circling the nucleus. This single electron gives the atom a charge, making it very attracted to other molecules. A molecule with an unpaired electron is said to be 'radicalized'. These radicalized compounds, or free radicals, can quickly react with other molecules. For this reason these compounds are also called reactive species. Oxygen is the most common reactive species found in the human body and when it acquires an extra electron it is called a reactive oxygen species (ROS).

Free radicals 'steal' an electron from a nearby molecule so that all of their electrons are in pairs. The affected target molecule would then become a radical. A chain reaction of electron 'theft' can occur within a cell. Free radicals can affect just about any structure in a cell, including DNA. If free radicals steal an electron from DNA, the genetic code can be damaged and cell function damaged. DNA damage caused by free radicals has been associated with aging, rheumatoid arthritis, inflammatory bowel disease, acute respiratory distress syndrome (ARDS), emphysema, and some types of cancer. ⁽⁶⁾⁽⁵⁾⁽⁷⁾

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Cancer Prevention: Antioxidants

A Closer Look at Free Radicals