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What is ORAC?
July 23, 2012
ORAC is an acronym for Oxygen Radical Absorbance Capacity. ORAC is one analytical method for measuring the ability of a given compound to neutralize free radicals. This method involves testing various foods in the laboratory (i.e., outside the body) to determine their antioxidant capacity. An antioxidant is a substance that helps to control oxidation, and antioxidant activity is defined as the ability to scavenge free radicals. The body uses a number of antioxidant molecules, some of which are produced in the body, such as glutathione and SOD (superoxide dismutase), and some that are consumed in foods, such as Vitamins A, C, and E. Many foods, especially fruits, vegetables, herbs, and spices are known for their antioxidant activity.
Free radicals are highly reactive molecules. Because they are so reactive, free radicals can damage any susceptible material, a process known as oxidation. One easily recognizable example of oxidation is that of rust forming on iron surfaces that are exposed to air. Free radicals also play an important role in biological processes. Some of these are necessary for life and play a positive role in cell physiology, including many normal metabolic functions like conversion of food into cellular energy. However, free radicals may also do great damage to cell membranes and DNA. When an imbalance develops between the effects of free radical damage and the body’s ability to cope with it, it is known as “oxidative stress.”
Scientists have long considered oxidative stress to be a significant contributor to cellular aging and an important factor in chronic disease. It is important to understand however, that multiple active types of free radicals and mechanisms of action are involved in the process of oxidative stress. Likewise, the body defends itself through various mechanisms to counteract it. Therefore, there is no simple universal method by which antioxidant capacity can be assessed accurately and quantitatively. However, laboratory assays such as ORAC provide one way of comparing relative activity.
A wide variety of foods has been tested via ORAC and the resulting values have been published in scientific journals and elsewhere. The results of these studies were compiled by the USDA (United States Department of Agriculture) and posted on their website as the ORAC Database for Selected Foods.
What happened to the USDA’s ORAC Database for Selected Foods from its website?
The USDA recently removed its ORAC database from their website. The USDA questions the relevance of ORAC values, which are measured outside of biological systems. This is because many “antioxidant” food constituents, such as polyphenols, have been found to have mechanisms of action inside the body that are unrelated to their antioxidant functions. Furthermore, it is evident that some polyphenols may have poor bioavailability or may be metabolized in the body to yield molecules with no antioxidant activity. The activities of these compounds and their metabolites are not well understood, although many have been associated with health benefits. The USDA therefore believes that consumers may misunderstand the ways in which these foods exert their health benefits by looking only at ORAC values. However, we believe that the USDA’s decision to remove the ORAC database is unfortunate and not in consumers’ best interests since no viable alternative is provided.
Does the withdrawal of ORAC database from USDA website mean that ORAC values were incorrect or meaningless? Does it mean that these foods or compounds have no beneficial role in health?
No. ORAC is only one measure of potential biological activity. It is a way of comparing different foods with respect to their ability to neutralize oxygen free radicals. Moreover, regardless of whether antioxidant food constituents have antioxidant activities in the body, scientists have established that many of them, polyphenols in particular, play important roles in human health, even if the roles they play involve mechanisms other than the quenching of free radicals. Although no substantial relationship between human health benefits or specific health conditions has been proven, many foods with high ORAC values have been shown to have potent positive activities in the body. Some examples of these are blueberries and green tea.
Are there other methods to measure antioxidant activity?
Yes. There are a number of methods used to measure antioxidant activity. TEAC (Trolox Equivalent Antioxidant Capacity), FRAP (Ferric Reducing Ability of Plasma), CUPRAC (Copper Reduction Antioxidant Capacity), and DPPH (2,2-diphenyl-1-picrylhydrazyl) are a few commonly used radical scavenging capacity assays. Each of these methods measures antioxidant capacity in a different way and some are more relevant to biological systems than others. ORAC is usually considered to be more relevant because it is reported to mimic antioxidant activity of phenols in biological systems. However, test results obtained by utilizing these other methods have not been compiled; therefore, no alternative third party database exists that consumers can use to help them compare the antioxidant activities of foods.
Is ORAC information still useful?
ORAC remains a valuable tool for consumers in determining the relative bioactivity of foods. In addition, ORAC values can be very important to the food industry because they provide information regarding shelf-life of foods. Another area of application of this technique is in the area of quality control because it helps set and maintain standards of freshness and overall food quality.
Will NOW foods continue to declare ORAC values on specific product labels?
Yes, NOW Foods will continue to provide this information for consumers.