Natural Foods Merchandiser

The story behind the ORAC numbers

At Brunswick Laboratories in Norton, Mass., they're very busy testing the antioxidant levels of beans, chocolate, goji berries—you name it. The largest third-party tester of ORAC (oxygen radical absorbance capacity), Brunswick has increased its business 30 percent each year for the last two to three years. "A lot of people are becoming more conscious that ORAC is important, that antioxidants are important," says lab technician Jillian Theobald. "People are also becoming more familiar with the ORAC scores and what they mean."

Perhaps obsessed is a better word. Virtually any new product with an antioxidant-rich ingredient claims its superiority, splashing its ORAC value across the label and, often, the Internet. The idea is the higher the ORAC score, the more antioxidants—and thus, the more disease-fighting capabilities—a food has. One manufacturer of grape concentrate-based products is even pushing The ORAC Diet. But amid all the hype, people are wondering if all the claims are valid, and whether a high ORAC score is all it's cracked up to be. The answer to both, it turns out, is a qualified no.

"A lot of it is competition—everyone wants to have the highest score. We're more concerned with products being healthy," says Theobald. "Unfortunately," she adds, "a lot of companies post their results online. Sometimes they do put deceiving ORAC results on the Web and that's difficult. I tell our customers to request from our company a copy of the report—if they're being honest they should be willing to publish that."

Theobald says other labs are testing ORAC but Brunswick's procedure is patent pending. "We developed it in conjunction with Dr. Ron Prior."

Prior may as well be considered, if not the father of ORAC, at least the godfather. Dr. Guohua Cao developed the test in 1992 at the National Institute of Aging in Bethesda, Md., but the method was somewhat cumbersome for frequent use. So in 1995, Cao joined Prior at the Jean Mayer USDA Human Nutrition Research Center at Tufts University in Boston, where they substantially updated the procedure, allowing it to become partially automatized and easily adaptable to evaluate a wide range of foods.

The glow of good food
In 2004, Prior, now at the Arkansas Children's Nutrition Center and Agricultural Research Service of the U.S. Department of Agriculture, further expanded the ORAC assay by developing a method to test both the hydrophilic (water-soluble) and lipophilic (fat-soluble) components of antioxidants, rendering a total ORAC score. Prior and his colleagues put more than 100 types of fruits, vegetables, nuts, seeds, herbs and spices through the precise testing process. That resulted in the database that is now widely used and cited.

When conducting an ORAC test, scientists introduce a free radical, namely peroxyl, to the sample being tested. "Then we use a probe that fluoresces. When it's attacked by the oxidant or free radical source, then it loses its capability to fluoresce. When you put an antioxidant in there it protects the probe until the antioxidant is used up," Prior says. The longer the probe fluoresces, and the greater the intensity of the glow, the higher the antioxidant capacity.

The mystery of ORAC
But ORAC values can vary within the same type of product. A March study published in Phytotherapy Research found that wheatgrass grown under four different conditions yielded four different ORAC values.

"The genetic background can affect it, but also growing season [and] conditions of growth affect it as well," Prior says. "A lot of compounds in the flavonoids tend to be produced in response to a stress on the plant, whether that's an insect infestation, drought or anything that might stress a plant. Time of harvest also impacts it because these [factors] tend to change with the maturity of the plant."

Other variables can also influence a food's antioxidant properties. In 2004, Prior and his colleagues found that cooking significantly affected antioxidant capacity, raising it in some foods but lowering it in others.

Other research shows that fresh produce may have a slight edge over frozen. "Four of six frozen vegetables showed lower phenolic and ORAC values than the fresh vegetables, whereas in the other two cases, values were significantly higher compared to fresh samples," authors Ninfali and Bacchiocca wrote in their 2003 article in the Journal of Agriculture and Food Chemistry.

What about when it comes to organic versus conventional produce? "Organic … could tend to be higher just because if you aren't using pesticides you could have insects that affect the plant and it might increase the [antioxidant] levels," Prior says.

Laboring over lab integrity
Prior also stresses that any given published ORAC value will depend on how the sample was collected. In his research, he and his colleagues sampled produce from stores in 12 U.S. cities representing four regions (West, Central, South and Northeast) in two different seasons, purchasing about 3 pounds of each item at any given store. But not everyone does this.

Theobald says some companies send in single samples of product while others send in hundreds to assure consistency from lot to lot. Brunswick charges $200 per sample for companies that want just the hydrophilic testing, and $450 for both hydrophilic and lipophilic. "I have heard of companies doing their own [testing] because they have to do so many tests … but when it comes to results that they can use for marketing, it would be really difficult to use their internal results and [have consumers] consider them reliable.

"Unless [a company] really comes out and says so, there is no absolute way to know who performed the testing," Theobald says. "I do have customers who put our name on their packaging."

It's also important that companies compare, um, apples to apples. Some common spices have high ORAC scores (ground cloves weigh in at 3,144) but people would rarely consume a "serving" of cloves as they would with apples (one Fuji nets an ORAC score of 3,578).

"We're in the process now of putting the procedure through a multi-lab validation … so it can become an industry standard. It's needed—there's an awful lot of other methods out there," Prior notes.

More than a score
"Having the largest number doesn't necessarily mean the best," Prior says. "It depends on the food and what phytochemicals are in there and what happens during the absorption and metabolism process. We're finding some of these compounds are metabolized extensively or not absorbed effectively and so not much gets into the blood or absorbed into the tissue."

Even if an antioxidant is effectively metabolized, it may not be sufficient. Each has its own strengths in terms of which free radicals it most effectively scavenges. So, in striving to meet the USDA's recommended level of 3,000 to 5,000 ORAC units daily, people need to consume a variety of types of antioxidants.

In a study published in the February 1999 issue of Agricultural Research, scientists at the Human Nutrition Center on Aging at Tufts University in Boston found that spinach, with an ORAC value of 1,260, was more neuroprotective in rats than strawberries, which rate 1,540 on the ORAC scale.

In other cases, the critical factor appears to be which particular antioxidant is present in a food and which free radical it's fighting. "Some of those that are highest [in ORAC]—particularly the berries—the compounds that are primarily responsible for their antioxidant activity are anthocyanins, which are the color compounds. Those are rather unstable and not that much gets absorbed. To get the same effectiveness you've really got to consume more than just the average," Prior says.

"There's nothing wrong with selecting foods that are higher on the list, but one's gotta realize that there are differences in the absorption process."

ORAC values per serving of common foods

Fresh Fruits (serving size: 1 cup)

Wild blueberry






Dried Fruits (serving size: 1/2 cup)



Dates (Deglet Noor)





Small red bean (1/2 cup)


Artichoke (1 cup hearts)


Russet potato (1 potato)


Nuts (serving size: 1 oz)







Spices (no serving size established)







Source: Journal of Agricultural and Food Chemistry, Vol. 52, No. 12, 2004

Natural Foods Merchandiser volume XXVII/number 7/p. 24, 28

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