While the word “antioxidant” has become pretty familiar to most of us, it’s much more than just an Internet buzzword for fitness gurus and food marketers. There is strong evidence that antioxidants can have a profound effect on our health and well-being. At the same time, researchers readily admit that our understanding of antioxidants and the way they work in the body is still very, very limited. With this caveat in mind, here’s a short—and relatively simple—briefing on antioxidants as well as the technique scientists use to measure the “antioxidant power” of various so-called “superfoods”.
What are antioxidants and what do they do anyway?
Antioxidants are substances that reduce the number of free radicals (or oxygen radicals) that form in the body as the result of physical activity or digestion, both of which increase oxidation. Just as iron rusts as a reaction to the presence of oxygen, the body reacts to the oxidation process by increasing the number of free radicals. And just as rust weakens iron, free radicals weaken the body by attacking its organs and cells, causing or contributing to diseases such as cancer, senile dementia and osteoarthritis.
How do you measure the “antioxidant power” of foods?
So now we know that antioxidants are good for us. But how do we know which foods contain the largest amounts of the most highly effective antioxidants? When it comes to this question, we have a bit of a measurement problem. With the exception of a few dietary supplements such as vitamins A, C and E, no foods have conclusively been proven to have high antioxidant efficiency in vivo (that is, in the bodies of human subjects). This means that regulatory agencies such as the FDA (and therefore consumers) must rely on in vitro (test tube) tests to compare the antioxidant capabilities of various foods.
The Oxygen Radical Absorbance Capacity (ORAC) test, developed by physician and chemist Guohua Cao, is a test tube analysis that measures the combined antioxidant efficiency of nutrients in common foods. Different fruits, vegetables and supplements have different ORAC scores. In theory, the higher the ORAC score a food or supplement receives, the more efficient it is as an antioxidant. At least in the test tube.
However, the ORAC score can be misleading. To legitimately compare two foods as antioxidants, you would have to be sure not only that the same amounts of each are measured, but also that the two foods have a similar composition. For example, raisins will have a higher ORAC score than grapes when comparing similar weights of each, but the difference is caused by the additional water in the fresh grapes. As a result, the ORAC scores of different fruits, vegetables, and supplements should be viewed as a general guideline, not as a hard-and-fast rule. And that’s BEFORE we get to the issue of comparing bioavailability—a factor that’s outside of the scope of the in vitro ORAC test.
There seems to be no question that adding antioxidant-rich foods to your diet can raise antioxidant levels in the blood by 10-25%. Experts recommend a daily intake of fruits, vegetables and supplements of around 5000 ORAC units. But the selection of which combination of fruits, vegetables and supplements to choose is up to you. You could potentially eat several fruits with low ORAC levels and achieve a total of only 1300 ORAC units, or you could eat a handful of blueberries and achieve a total score of 6000 ORAC units.
So in the final analysis, the ORAC scores you see on food labels or in charts should be considered a useful pointer in the direction of the more antioxidant-rich foods, enabling you to make more informed nutritional choices. Using your common sense about eating a balanced, varied diet with lots of colors is still the best policy. Eating several servings a day of fruits and vegetables (especially dark greens) should enable you to keep your body well supplied with healthy antioxidants—whether or not you add up their ORAC scores!
