Oxygen radical absorbance capacity (ORAC) is a method of measuring antioxidant capacities in biological samples in vitro.
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and legumes rated highly in extensive tables once published by the United States Department of Agriculture (USDA), but withdrawn in 2012 as biologically invalid, stating that no physiological proof in vivo existed in support of the free-radical theory. Consequently, the ORAC method, derived only in in vitro experiments, is no longer considered relevant to human diets or biology by the USDA.
Not all have been so unilaterally dismissive. Former ARS-USDA scientist Ronald Prior, Ph.D., sent a letter to the USDA in response to their removal of the database, writing that it had utility when taken in context of epidemiology and disease endpoints. Prior also disagreed that there was no evidence that the beneficial effects of polyphenol-rich foods can be attributed their antioxidant properties. He cited research using the ORAC database that found lower rates of endometrial cancer in those consuming the highest phenolics. Alternative measurements include the Folin-Ciocalteu reagent, and the Trolox equivalent antioxidant capacity assay.
Read more about Oxygen Radical Absorbance Capacity: Method, Regulatory Guidance, Physiological Context, Food Sources, Comparisons of ORAC Values
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