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A Mouthful of Science:
Oxygen Radical Absorbance Capacity (ORAC) - What Is It?

In a number of Dr. Gourmet articles I have talked about various foods that are high in antioxidants. Understanding antioxidants and oxidation can be a bit challenging and we get mail from readers asking about just what this means.

Download a USDA guide to the ORAC in foods. (PDF document)

Antioxidants are molecules that have the power to help prevent oxidation. What happens is that various molecules in your body will give up an electron to another molecule, the oxidizing agent. That oxidation can produce molecules known as free radicals which can set up a chain reaction of oxidation that damages cells. Antioxidants can not only stop that chain reaction, they can also prevent the initial oxidizing step, hence the name anti-oxidants. There's a wide variety of antioxidants, including vitamin C (ascorbic acid), vitamin E and its isomers (tocopherols and tocotrienols) and selenium. There are also carotenoids, isoflavones, flavonoids and proanthocyanidins.

Recent research has established links between oxidation and the development of many chronic and degenerative diseases, such as cancers and heart disease, as well as neurologic conditions like Alzheimer's and Parkinson's disease. So-called "oxidative stress" has also been linked to the aging process and it's felt that this is through the damage done to the body's proteins, fats and DNA.

Fruit, nuts, vegetables, seeds, seed oils, tea and coffee have long been considered to be excellent sources of antioxidants.

One way to look at the relative value of these ingredients is the ORAC assay. The method developed by Prior, et al evaluates both hydrophilic (water soluble) as well as lipophilic (fat soluble) antioxidants. In a study commissioned by the USDA and the Produce for Better Health Foundation, values were calculated and reported for both hydrophilic-ORAC (H-ORAC) and lipophilic-ORAC (L- ORAC) as well as total-ORAC.*

ORAC values allow one to compare the relative value of antioxidants for tested foods. The one consideration is that people will focus on the ORAC value itself and believe those foods with the highest value as being naturally good for them, but be cautious. All of the ORAC values are reported for 100 grams by weight (about 3 1/2 ounces) of the ingredient measured. There is, however, a vast difference between 3 1/2 ounces of apple and the equivalent measure of alcohol or coffee.

For example, curry powder seems very high in antioxidants at an ORAC value of about 25,000. That said, the jar of curry powder in my spice drawer is only 1.4 ounces. It contains about 1/2 cup or 24 one teaspoon servings which comes to an ORAC value of 417 per serving. That's not bad, but when comparing apples with oranges with coffee with chocolate with curry powder it's crucial to consider the serving size. 100 grams of coffee is essentially calorie free, but the same weight of chocolate will set you back over 500 calories. Dark chocolate may have a very high ORAC value, but it comes with sugar and a lot of added calories.

Recently we've had folks write in about eating dark chocolate for their health, and while choosing chocolate as your treat is a great idea, remember that there are many other foods that are really high in antioxidants. Choosing fruits and veggies and nuts and great quality oils and coffee or tea along with some chocolate is a great strategy.

Timothy S. Harlan, M.D.
Dr. Gourmet
December 27, 2010

* Note that when only an H- ORAC value was available for a particular food item low in fat, H-ORAC value was also utilized for the Total ORAC value. In some cases values for H-ORAC, L-ORAC and Total-ORAC may come from different sources, and the sum of the average values for H- ORAC and L-ORAC may not equal the value for Total-ORAC.