ORAC

Oxygen radical absorbance capacity (ORAC) is a method of measuring antioxidant capacities in biological samples in vitro.[1][2]

A wide variety of foods has been tested using this method, with certain spices, berries and legumes rated highly in extensive tables once published by the United States Department of Agriculture (USDA), but withdrawn in 2012 since no correlation between test results and biological activity could be determined,[3] stating that no physiological proof in vivo existed in support of the free-radical theory.

Food sources

Values are expressed as the sum of the lipid soluble (e.g. carotenoid) and water-soluble (e.g. phenolic) antioxidant fractions (i.e., “total ORAC”) reported as in micromoles trolox equivalents (TE) per 100 gram sample, and are compared to assessments of total polyphenol content in the samples.

These values are considered biologically irrelevant by the EFSA and USDA.[3][10]

Food ORAC scores – USDA
FOOD SERVING SIZE ORAC, TROLOX EQUIV., ΜMOL PER 100 G
Prune 1 cup 14,582
Small Red Bean ½ cup dried beans 13,727
Wild blueberry 1 cup 13,427
Red kidney bean ½ cup dried beans 13,259
Pinto bean ½ cup 11,864
Cranberry 1 cup raw (whole berries) 9,584
Blueberry 1 cup raw (cultivated berries) 9,019
Artichoke hearts 1 cup, cooked 7,904
Raw unprocessed Cocoa bean 1 oz 7.840
Blackberry 1 cup raw (cultivated berries) 7,701
Raspberry 1 cup 6,058
Strawberry 1 cup 5,938
Red Delicious apple 1 apple 5,900
Granny Smith apple 1 apple 5,381
Pecan oz 5,095
Sweet cherry 1 cup 4,873
Black plum 1 plum 4,844
Russet potato 1, cooked 4,649
Chokeberry 1 oz 4,497
Black bean ½ cup dried beans 4,181
Plum 1 plum 4,118
Gala apple 1 apple 3,903
Pomegranate 100 grams 2,860

With nearly all vegetables, conventional boiling can reduce the ORAC value by up to 90%, while steaming retains more of the antioxidants.[15]

Comparisons of ORAC values

The United States Department of Agriculture, previously a publisher of ORAC data, withdrew its web publication of ORAC values for common American foods in 2012 due to absence of scientific evidence that ORAC has any biological significance.[3]

When comparing ORAC data, care must be taken to ensure the units and food being compared are similar. Some evaluations will compare ORAC units per gram of dry weight of the intact food or its milled powder, others will evaluate ORAC units in fresh or frozen wet weight, and still others will look at ORAC units per serving. Under each evaluation, different foods can appear to have higher ORAC values. For example, although a raisin has no more antioxidant potential than the grape from which it was dried, raisins will appear to have a higher ORAC value per gram of wet weight than grapes due to their reduced water content. Likewise, the large water content in watermelon can make it appear as though this fruit is low in ORAC. Similarly, the typical quantity of food used should be considered; herbs and spices may be high in ORAC, but are applied in much smaller quantities compared to intact whole foods.[16]

Numerous health food and beverage companies and marketers have erroneously capitalized on the ORAC rating by promoting products claimed to be “high in ORAC”. As most of these ORAC values have not been independently validated or subjected to peer review for publication in scientific literature, they remain unconfirmed, are not scientifically credible, and may mislead consumers.

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