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Antioxidants are substances that slow or prevent the oxidation process from damaging the body’s cells. They also repair cell damage, and may improve immune system functioning and lower the risk of infection and cancer.

Antioxidants protect the body from damage caused by unstable molecules known as free radicals. These are molecules that have one or more unpaired electrons. Every cell in the body needs oxygen to produce energy. However, when cells burn oxygen, they create free radicals. Environmental factors such as cigarette smoke, air pollution, radiation and ultraviolet light also can cause free radicals to form in the body.

An unpaired electron makes a free radical unstable and highly reactive. In order to become stable, free radicals seek out and take electrons from body cells. This damages the cells, depriving them of an electron, leaving them unstable and resulting in the formation of another free radical. The new free radical then seeks to take an electron from another cell, creating a chain reaction of free-radical creation that can continue indefinitely.

Occasionally, free radicals are helpful to the body. For example, the immune system may use them to kill disease-causing viruses and bacteria. However, more often, free radicals inflict damage to healthy cells and DNA (which contains the genetic code for human cell reproduction). This can lead to many health problems, including:

• Age-related deterioration, such as wrinkling of skin
• Artery and heart disease
• Cancer
• Cataracts (clouding of the eye lens)
• Diabetes

The body’s natural defenses try to limit the damage of free radicals and to repair damaged cells. For example, certain enzymes in the body also work as antioxidants to neutralize harmful substances. However, the effectiveness of this activity is limited and decreases as a person ages. 

Antioxidants provide extra help in the body’s fight against free radicals. Antioxidants prevent free radicals from damaging cells by donating electrons to free radicals. When an antioxidant loses an electron, it remains stable and thus does not itself become a free radical. Antioxidants that donate an electron to a free radical neutralize the free radical or convert the molecule into waste to be eliminated by the body. They also may help repair cells already damaged by free radicals.

Much remains to be learned by scientists about antioxidants, and many of the claims made about antioxidants have not yet been conclusively proven. Experts remain unsure of exactly how antioxidants work to help prevent illness.

Scientists believe that antioxidants may protect people from certain diseases (e.g., arthritis, cancer, cataracts, heart disease) and may slow the degenerative process that accompanies aging.  For example, studies have shown that people who eat generous amounts of fruits and vegetables (which are high in antioxidants) have lower rates of cancer. However, experts cannot yet definitively say that this is due to the antioxidant content of these foods.

Researchers continue to look for evidence of links between antioxidants and good health. For example, researchers at Ohio State University recently found evidence that combining antioxidant treatment with the use of a certain type of heart drug may help the heart recover better following a heart attack.

Other recent studies have found evidence that antioxidants may:

• Help slow vision loss caused by eye diseases such as retinitis pigmentosa.

• Protect against tick-borne illness such as Rocky Mountain spotted fever.

• Shield the lungs from damage in patients with silicosis, which results from exposure to crystalline silica.

While these studies are promising, they have not yet been confirmed. In addition, other recent studies seem to undermine some of the commonly held assumptions about antioxidants.

For example, researchers at Oregon State University found evidence that flavonoids have little or no value as antioxidants, although they may contain other health benefits.