ORAC (Oxygen Radical Absorbance Capacity)


What is ORAC - Oxygen Radical Absorbance Capacity ?

There are several methods which have been developed to measure the total antioxidant capacity of biological samples. But the ORAC (Oxygen Radical Absorbance Capacity) method is unique, acording to developer Guohua Cao.

ORAC measures the degree to which a sample inhibits the action of an oxidizing agent and also how long it takes to do so.
Then it integrates the two measurements into a single unit.
This provides an accurate and reproducible measurement for the different types of antioxidants having different strengths.

ORAC stands for Oxygen Radical Absorbance Capacity. This is it's capacity for fighting free radicals which are the cause of cancers, reduced immune system capabilities and other diseases.

One of the best ways to fight free radicals is by choosing the right foods.
This is where ORAC is important. ORAC is a way to measure how many free radicals a specific food can absorb. The more free radicals a food can absorb, the higher its ORAC score. The higher its ORAC score, the better it is at helping our bodies fight diseases like cancer and heart disease and other diseases.

Plant foods have the highest ORAC scores are are best at fighting disease.

Generally, brightly colored foods tend to be the ones with the highest ORAC scores. This means these are the foods that help fight disease the best by stopping free radicals from causing damage in our bodies. Think bright reds, greens, oranges, blues, purples, yellows, and oranges. What foods do these words describe? Strawberries, spinach, blueberries, blackberries, eggplant, yellow peppers, carrots, and oranges. Any brightly colored fruits and vegetables that you can think of are good for you to include in your diet EVERY DAY! As a matter of fact, research shows that people who eat more of these plant foods have lower risk of cancer!

Oxygen radical absorbance capacity (ORAC) assay for antioxidants.

Cao G, Alessio HM, Cutler RG.
Gerontology Research Center, National Institute on Aging, NIH, Baltimore, MD 21224.

A relatively simple but sensitive and reliable method of quantitating the oxygen-radical absorbing capacity (ORAC) of antioxidants in serum using a few microliter is described. In this assay system, beta-phycoerythrin (beta-PE) is used as an indicator protein, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) as a peroxyl radical generator, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox, a water-soluble vitamin E analogue) as a control standard. Results are expressed as ORAC units, where 1 ORAC unit equals the net protection produced by 1 microM Trolox. The uniqueness of this assay is that total antioxidant capacity of a sample is estimated by taking the oxidation reaction to completion. At this point all of the nonprotein antioxidants (which include alpha-tocopherol, vitamin C, beta-carotene, uric acid, and bilirubin) and most of the albumin in the sample are oxidized by the peroxyl radical. Results are quantified by measuring the protection produced by antioxidants. This solves many problems associated with kinetics or lag-time measurements. A linear correlation of ORAC value with concentration of serum. Trolox, vitamin C, uric acid, and bovine albumin is demonstrated. The coefficient of variation within a run is found to be about 2% and from run to run about 5%. Trolox, alpha-tocopherol, vitamin C, beta-carotene, uric acid, and bilirubin completely protect beta-PE from oxidation, while bovine albumin protects beta-PE only partially. On a molar basis, the relative peroxyl radical absorbance capacity of Trolox, alpha-tocopherol acid succinate, uric acid, bilirubin, and vitamin C is 1:1:0.92:0.84:0.52. Bovine albumin per unit weight has a lower peroxyl absorbing capacity than these antioxidants.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 8458588 [PubMed - indexed for MEDLINE]