Oxygen radical absorbance capacity

Oxygen Radical Absorbance Capacity (ORAC) is a method of measuring the antioxidant capacity of different foods and supplements. It was developed by scientists at the National Institutes of Health (NIH) and the Agriculture Research Service (ARS), the principal intramural scientific research agency of the United States Department of Agriculture (USDA).

History

The ORAC method was first described in a 1992 publication by Guohua Cao and colleagues at the NIH. The method was later refined by the ARS's Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts.

Methodology

The ORAC assay measures the degree to which a sample inhibits the action of an oxidizing agent, peroxyl radical. The peroxyl radical is one of the most common reactive oxygen species (ROS) in the human body. Antioxidants in the sample are oxidized by the peroxyl radical, and the loss of antioxidant activity is measured over a fixed period of time.

Applications

The ORAC value of a food or supplement can provide a measure of its antioxidant capacity, which is believed to play a role in the prevention of diseases such as cancer and heart disease. However, the relationship between ORAC values and health benefits is still under investigation, and the USDA removed its ORAC database from its website in 2012 due to concerns about the misuse of ORAC values in food and supplement marketing.

Criticisms

Critics of the ORAC method argue that it is not a true measure of antioxidant capacity, as it only measures the capacity of antioxidants to scavenge peroxyl radicals, and not other types of ROS. Furthermore, the ORAC method does not take into account the bioavailability of antioxidants, or the extent to which they are absorbed and utilized in the body.

See also

• Antioxidant
• Reactive oxygen species
• Free radicals
• Bioavailability