Antioxidants are molecules that – as the name implies – slow the process of oxidation in the body. Although oxidation is a crucial part of living, too much of it can be damaging, because normal oxidation reactions that occur as food is digested can produce free radicals (or oxygen radicals), which in turn can cause chain reactions that trigger cell death or damage.
The same way that iron reacts to oxygen by producing rust, your body reacts to its internal oxidation process (digestion) by producing increased numbers of free radicals. And in the same way that rust weakens the iron, oxidation weakens the body, because the free radicals then attack cells and organs, contributing to diseases such as cancer, coronary heart disease, stroke, Alzheimer's disease, rheumatoid and osteoarthritis, and cataracts.
You can counteract this oxidation process by adding antioxidant-rich foods to your diet. Antioxidants retard or block the oxidation process by neutralizing free radicals. In the process of doing this, however, the antioxidants themselves become oxidized, so we have to keep taking them to replenish our body's antioxidant resources.
What are some known antioxidants?
Most of the antioxidants clearly recognized by science are vitamins and minerals such as Vitamin E (especially alpha-tocepherol, which has the highest biopotency), Vitamin C, beta-carotene, selenium, manganese, and zinc. There are also antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and catalase that have been proven to destroy free radicals and thus slow the production of free radicals. In addition, other nutrients that have been shown to have antioxidant qualities include coenzyme Q10 (ubiquinone) and uric acid. And there is a growing body of research on naturally occurring phytochemicals in fruits, vegetables and other foods that have antioxidant qualities and thus may promote health.
But which foods are effective antioxidants? With the exception of the vitamins and dietary supplements discussed above, no foods have been conclusively proven to have to have high antioxidant efficiency in human subjects (in vivo). So consumers and the FDA must rely on test tube (in vitro) tests to compare the antioxidant capabilities of different foods.
What is the ORAC scale, and can it be believed?
One of the things you may see on the labels of nutrients and supplements is their ORAC score. The Oxygen Radical Absorbance Capacity (ORAC) scale is a test tube analysis that measures the antioxidant efficiency of common foods. In theory, the higher the ORAC score given to a food or supplement, the more efficient it is as an antioxidant.
In reality, the ORAC score can be confusing. To legitimately compare two foods, you have to be certain that the same amounts of each food are measured, and that they have a similar consistency. For example, a handful of raisins will be listed as having a higher ORAC score than the same size handful of grapes, but the fresh grapes contain more water, so there are fewer nutrients for the same amount of weight. So the ORAC scores given to foods should be viewed as general guidelines, not as indisputable facts.
Nutrition experts recommend a daily intake of approximately 5000 ORAC units, composed of fruits, vegetables, and supplements. But the selection of which fruits, vegetables, and supplements is up to you. You could eat several fruits with low ORAC scores and total only 1300 ORAC units, or you could eat a smaller amount of blueberries and total 6000 ORAC units.
So when it comes to antioxidants, as with so many other foods or supplements, the information you find on package labels or in government charts should be thought of as suggestions to help you make wiser dietary choices. Use your own common sense. If you make sure that your diet contains the recommended amounts of fruits, vegetables, and dark greens, that should keep your body well supplied with antioxidant nutrients.