ORAC and Antioxidants: Realizing the Potential

The idea of antioxidants and the abundance of antioxidant products on the market have become more widely accepted by consumers. People understand “the good guys vs. the bad guys”, so antioxidants vs. free radicals is a match-up they can tune in to. People also agree the jam-packed, average modern lifestyle has created a food culture of nutritional deficiencies and quick fixes. They realize their diet and genetic make-up is not sufficiently armed to deal with the increase in free radicals such lifestyles have created. Thus, they are willing, even eager, to supplement with antioxidants.

Little do they know, the world of antioxidants and oxidation is quite complex, and the marketplace for antioxidant supplements is riddled with misleading, inconsistent or inaccurate marketing and labeling. Sure, marketers’ hands are somewhat tied by federal regulations on what they can say about the benefits of dietary supplements and functional foods; but, consumers looking for results show no mercy when a product fails to deliver what they perceive should be the benefits.

To summarize this complex category: antioxidants can act generally and/or specifically, and the marketing of antioxidants using Oxygen Radical Absorbance Capacity (ORAC) and similar test scores is largely about potential.

In the mid-1990s, Ronald Prior, Ph.D., at USDA's Human Nutrition Research Center on Aging at Tufts University, Boston, joined forces with the team that first published the ORAC assay principles—physician and chemist Guohua Cao, M.D., Ph.D., and his colleagues at the National Institute on Aging (NIA), Bethesda, Md.—to apply the test to food evaluation. The test pits an antioxidant sample—an extract, for example—against free radicals in a test tube. The amount of oxidative stress/damage and inhibition of this oxidation is measured relative to a fluorescent tube, yielding a score that represents the antioxidant capacity of the sample.

To understand what ORAC scores really mean to human health and the diet, it is important to first grasp the differences between various antioxidant compounds and their mechanisms of action. “Consumers are not fully aware of the existence of both water-soluble antioxidants (vitamin C) and fat-soluble antioxidants (vitamin E),” said W.H. Leong, vice president of Carotech Inc. “Each category of antioxidants works best in different parts of cells, and they work synergistically to confer the optimum antioxidant protection.”

This is key because the original ORAC test was water-based; thus, a water-soluble antioxidant, such as vitamin C, would generate a higher ORAC score than a fat-soluble antioxidant, like vitamin E. This does not mean vitamin E is less worthy an antioxidant.

“What is important to understand is that each antioxidant has its own unique properties and works best in different parts of cells,” Leong stressed. “Vitamin C may be most effective in the cytosol of a cell (aqueous part), whereas vitamin E is most effective in the membrane bilayer and mitochondria (fat part) of a cell.”

Brunswick Labs, which has long worked with Prior on improving the ORAC test, has recently expanded the ORAC test to be suitable for both water- and fat-soluble antioxidants; however, the test still only measures activity against peroxyl radicals and hydroxyl radicals. There are at least four other harmful reactive oxygen species (ROS)—hydrogen peroxide, superoxide anion, singlet oxygen and peryoxynitrite—that cause oxidative problems to human lipids, proteins and DNA. However, Brunswick has recently developed versions of ORAC to test for peryoxynitrite (NORAC test) and hydroxyl radicals (HORAC). Also, it is currently developing an assay for singlet oxygen, under a recent federal grant. But until these new assays make their mark, the limitations of the main ORAC test permeate the market.

“Antioxidants such as carotenoids (which do not have high ORAC values) are excellent against singlet oxygen, but do not work well against peroxyl radicals, hence the low ORAC score,” noted Charles DePrince, president of Fuji Health Sciences. “A high ORAC value, by itself, only indicates part of the protection; Unfortunately, ORAC, from a marketing view, tends to simplify the otherwise complex biological antioxidant system needed for good human health.”

People like simple, but not misleading. What, then, is the simple value of ORAC to consumers? Susanne Mertens-Talcott, Ph.D., a researcher in the Nutrition and Food Science Dept., Texas A&M University, College Station, said ORAC is currently used to characterize and compare a multitude of antioxidant fruit- and vegetable-based products.

“The ORAC value tells us that a given amount of the tested product has the same radical scavenging capacity as a known amount of a water-soluble form of vitamin E, to which the assay is standardized,” she explained. “Because this assay is standardized to vitamin E, it enables us to compare among different products, and makes it a valuable indicator for its potential to promote wellness and prevention of disease.”