Antioxidants
Antioxidants are substances that help neutralize the harmful effects of free radicals in the body, which are reactive chemicals that can cause cell damage through mutations in DNA and destruction of proteins and lipids. The accumulation of such damage is linked to the aging process and various degenerative diseases. While the body produces both antioxidants and free radicals, the natural supply of antioxidants can be limited, necessitating dietary sources such as fruits and vegetables. Key dietary antioxidants include vitamin E, vitamin C, and beta-carotene, which are known for their protective roles against health issues like cardiovascular disease and cognitive decline. Although extensive research supports the health benefits of antioxidants, definitive evidence on their effectiveness in preventing age-related diseases remains limited. Additionally, the optimal levels and sources of antioxidants—whether through supplements or whole foods—are still subjects of debate. It is generally recommended that individuals consume five to eight servings of fruits and vegetables daily to ensure adequate antioxidant intake. However, the role of antioxidant supplements is controversial, as they may not provide the same benefits as whole food sources and could potentially interfere with the body's natural processes.
Antioxidants
Anatomy or system affected: All
Definition: A group of vitamins, minerals, and enzymes that may help to protect the body from damage-causing free radicals
Free Radicals and Cell Damage
The role of antioxidants in preventing cell damage by free radicals has received considerable interest in recent years. Antioxidants are substances that may neutralize the harmful effects of free radicals in the body. Free radicals are highly reactive chemicals that form in normal metabolism or are produced by radiation and environmental stress. These volatile chemicals react with cell components, causing mutations in deoxyribonucleic acid (DNA) and destroying cell proteins and lipids. The aging process and various degenerative diseases are believed to be caused in part by the lifetime accumulation of cell damage caused by free radicals. Both antioxidants and free radicals are produced naturally by the body to help the body stay in a balanced state of health. Aging, stress, and pollution all damage DNA in the cells. Antioxidants may provide protection and reduce the risk of stroke, heartdisease, cancer, and other health problems associated with aging.
Antioxidant defenses occur naturally in the body to inactivate free radicals and repair damaged tissues. The body’s natural supply of antioxidants is limited, however, and a small amount of destruction occurs to cells daily. Dietary antioxidants—in the form of fruits and vegetables or vitamin supplements—are believed to improve health and to prevent cell damage by boosting the body’s natural supply of antioxidants.
Extensive research, including many large-scale studies, has demonstrated the beneficial role of dietary antioxidants in preventing such age-related disorders as cardiovascular disease, cancer, immune dysfunction, brain and neurological disorders, and cataracts. Fruits and vegetables, long recognized for their protective and healthful effects, are particularly rich sources of antioxidants.
Important Antioxidants
Vitamin E, vitamin C, and beta-carotene are the main dietary antioxidants. Vitamin E (tocopherol) is a fat-soluble antioxidant found in oil, nuts, seeds, and whole grains. This antioxidant appears to protect arteries against damage. In addition, the results of Women's Health Study suggest that taking natural-source vitamin E may help to reduce the risk of cardiovascular mortality. Vitamin C (ascorbate) works in the water-soluble part of tissues. Citrus fruits, strawberries, sweet peppers, and broccoli are good sources of vitamin C. This antioxidant boosts the immune system, strengthens blood vessel walls, and increases levels of a natural antioxidant, glutathione. Vitamin C also helps restore levels of active vitamin E in the body. Beta-carotene, a precursor of vitamin A, is found in carrot juice, sweet potatoes, and apricots. The Physicians' Health Study has found that taking beta-carotene slowed cognitive decline.
Other antioxidants include lycopene, lutein, coenzyme Q10, gingko, lipoic acid, grapeseed, and various substances found in green and black teas. The micronutrients zinc and selenium also have antioxidant properties; they aid the immune system and boost the levels of natural antioxidant enzymes in the body. Antioxidants appear to work together, as a combination of antioxidants is more potent than each substance alone.
Perspective and Prospects
Evidence for the beneficial role of antioxidants in human health is limited. Clinical studies have not definitively confirmed whether consuming large amounts of antioxidants offers increased protection against aging or age-related diseases. It is not clear what the optimal levels of antioxidants are to prevent the damaging effects of free radicals. Adequate levels of vitamins may vary greatly for each person, depending on levels of environmental stress, smoking, how well supplements are absorbed, and other factors. In addition, it is unclear whether vitamin supplements are superior to fruits and vegetables, since other factors in these foods (fiber, micronutrients) may be responsible for their healthful effects. There is also research suggesting that consuming large amounts of antioxidants may be harmful for individuals with cancer due to the same cell-protecting properties for which they have been promoted as a preventive for other conditions.
In general, people who eat five to eight servings of fruits and vegetables per day are thought to be getting an adequate amount of antioxidants. Taking antioxidant supplements is controversial, as some researchers believe that they may interfere with the body’s natural production of antioxidants.
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