Antioxidants Explained: Why These Compounds Are So Important

Found in many foods, antioxidants fight the oxidation process, a chemical reaction that can cause damage to many cells in your body


A lot of hype surrounds a group of compounds found in food called antioxidants. They are touted as everything from disease fighters to memory protectors to the antidote to aging. What are these compounds? Why are they important? And should you take supplements to get enough (or more) in your diet?


Antioxidants help fight oxidation, a normal chemical process that takes place in the body every day. It can be accelerated by stress, cigarette smoking, and alcohol. When there are disruptions in the natural oxidation process, highly unstable and potentially damaging molecules called free radicals are created. Oxygen triggers the formation of these destructive little chemicals, and, if left uncontrolled, they can cause damage to cells in the body. It's much like the chemical reaction that creates rust on a bicycle or turns the surface of a cut apple brown.

Free Radicals

These free radicals are atoms or groups of atoms that contain an odd number of electrons. They can be formed when certain molecules interact with oxygen. Once formed, free radicals can start a chain of damaging chemical reactions. The biggest danger to the human body is their potential to react with cellular components like DNA or the cell membrane, causing cells to function poorly or die.

Free radicals are not only generated by the body, they are present in foods you eat as well as in the air you breathe. Some even come through exposure to sunlight that can harm the eyes and the skin. Free radicals can trap a low-density lipoprotein (LDL) in an artery wall and begin the formation of plaque; they can damage DNA; or they can change the course of what enters and leaves a cell. Any of these actions can be the start of a disease process.

How the Body Defends Against Oxidative Stress

Oxidative stress occurs when the production of free radicals goes beyond the protective defenses in the body. Oxidative stress and free radical damage to cells may initiate the early stages of cancer and heart disease. Free radicals are also suspect in the development of Alzheimer's disease, arthritis, cataracts, diabetes, kidney disease, and age-related blindness.

The human body is not without its own defenses against this damage. It creates many different types of molecules --  antioxidants -- to combat these free radicals and protect the cells from attack by oxygen. Antioxidants can safely interact with free radicals and stop the chain of damaging reactions before damage is done to cells. There are several enzyme systems in the body that scavenge free radicals, but we can also gain these helpful molecules from foods that we eat. Some vitamins are antioxidants, such as vitamins C and E. Some minerals are antioxidants, such as selenium and manganese, and there are plant compounds that act as antioxidants such as beta carotene and lycopene, terms you may have heard before or seen in ads for vitamin supplements.


Many foods are good sources of antioxidants. The table below shows several types of antioxidants, their possible effects, and food sources of each. The big thing to notice is that antioxidants are found primarily in plant foods. The antioxidant minerals, selenium and manganese, are found in small quantities in meats and seafood, but the primary food source of all antioxidants is plant foods.


There is a huge range of antioxidant systems, and scientists haven't yet determined exactly how all the different systems work together in our bodies to protect us from free-radical damage. No one antioxidant can provide the protection offered by the many antioxidants working together.

The best way to get a variety of antioxidants in the diet is to eat foods that represent all the colors of the rainbow. Each color provides its own unique antioxidant effects. Bright orange, deep yellow fruits and vegetables like carrots, sweet potatoes, and apricots provide one type of antioxidant. Red foods like tomatoes, provide another. Green vegetables, such as broccoli and cabbage, and blue or purple foods, like blueberries and eggplant, each have their own antioxidant packages. Curcumin, the substance that makes turmeric yellow, is also believed to offer benefits.


Scientists began to theorize that free-radical damage was involved in the early stages of atherosclerosis and might play a role in the development of many other chronic medical conditions in the 1990s. Studies at the time suggested that people who ate few antioxidant-rich fruits and vegetables had a greater risk of developing these medical conditions. So began several clinical trials in which antioxidant supplements like beta carotene and vitamin E were tested for their protection against heart disease, cancer, and other conditions.

As a result, "antioxidants" became a buzzword in the '90s, and their benefits were glorified by the media, by the the food industry who began labeling foods as "rich in antioxidants," and by the supplement industry as they began hyping the health benefits of antioxidant supplements. They were even promoted as anti-aging ingredients in beauty products.

False Hype Regarding Aging and a Risk to Prostates

However, the research results were mixed and the anticipated benefits were not clearly present. While some trials reported beneficial effects, especially on cognitive decline, the hope that vitamin E would protect against heart disease and cancer did not pan out as anticipated. In fact, at least one study showed that taking antioxidant supplements increased the risk of lung cancer in smokers, and most recently, vitamin E was found to increase the risk of prostate cancer. As much as we would like to think a compound in food can forestall aging, antioxidants are not likely the answer.

Despite the lack of definitive research, antioxidants are still being promoted as food additives and supplements that can prevent a plethora of medical conditions including heart disease, cancer, cataracts, and memory loss, and they are still advertised as active ingredients in anti-aging products.

Important for the Eyes

Perhaps the most promising area in antioxidant research is the area of eye health. A study found that a combination of the antioxidants beta carotene, vitamins C and E, and the mineral zinc reduced the risk of developing advanced stages of age-related macular degeneration (AMD) in those who had intermediate or advanced AMD in one eye.


Whether they are taken singularly or in combination concoctions, antioxidants could have adverse health effects, as the prostate cancer and lung cancer studies mentioned earlier suggest. Supplementation has also been linked to an increased risk of skin cancer in women. Another study indicated that those who took vitamin A, E, and beta carotene supplements may be at risk for premature death. Excessive intake of vitamin E has also been associated with heart failure and increased bleeding.

The Food and Drug Administration does not regulate dietary supplements, and they can be sold with little or no research as to their safety, purity, and effectiveness. Dietary supplement manufacturing methods are not always standardized, so how well they work and their side effects can differ between brands or even within a brand. The form of a dietary supplement purchased in a drug store or health food store is likely not the same form used in research. The long-term effects of supplemental antioxidants are not known.


Despite numerous studies, no substantial health benefits have been demonstrated for supplemental antioxidants. Antioxidants in food, however, are considered safe.

Until there is more conclusive research, the best source of antioxidants is a diet rich in fruits, vegetables, and whole grains. Health organizations such as the American Heart Association, the American Cancer Society, and the American Institute for Cancer Research recommend getting antioxidants from food instead of supplements until research determines whether supplements are safe and provide the same benefits as antioxidants found naturally in food. There is plenty of research that suggests that whole grains, fruits, and vegetables, all of which contain extensive networks of antioxidants, are beneficial to health.

The best assurance of consuming adequate amounts of protective antioxidants is to eat between five and nine servings of fruits and vegetables representing all the colors of the rainbow every day. Snacking on small amounts of nuts and consuming wine in moderation also contribute to antioxidant consumption.

To prevent the "biological rust" that oxidation and the stress of life can wreak on your cells, help them help themselves by choosing your foods wisely. Your cells need the variety of antioxidants provided by different foods to fight the destructive little molecules that wage war in the body on a daily basis.

Image: JIANG HONGYEN/Shutterstock.

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