Oxygen Radical Absorbance Capacity (ORAC)

ORAC is a standardised test adopted by the U.S. Department of Agriculture to measure the Total Antioxidant Potency of foods and nutritional supplements. This standardised test was developed by Dr. Guohua Cao, a physician and chemist at the National Institute on Ageing in Baltimore, Maryland. It provides a very precise way of establishing the Free Radical destroying or neutralising power of a particular food, supplement or compound. The ORAC unit has become one accepted industry standard for measuring antioxidants. The antioxidant test combines a measure of both the time an antioxidant took to react and also its antioxidant capacity in a given sample. The ORAC unit then combines them into one measure, making it the first in vitro assay method for measuring total antioxidant potential. It is easily expressed as per 100 grams of sample.

Antioxidant books     Books on ORAC foods

The recommended daily antioxidant dose should add up to 5000 ORAC units each day. Looking at Table 1 below, it is clear that one has to be quite selective in the foods chosen so as to easily achieve this. If you at bananas alone, you would need to eat 2.4 kilograms of bananas to get your daily ORAC dose! You would however, only need to eat 87 grams of prunes. In a study of 36 older people, boosting fruit and vegetable intake to reach 3,200 ORAC units a day increased the antioxidant potential of the blood by 10 to 15%; enough to have an impact on disease prevention (Holly, 2003).

AIM Barleylife is as effective as the Chinese wolfberries as an antioxidant, with an ORAC value of 25,500! For anybody who could handle the smell, a drop of clove oil would give the required ORAC dose. There are however doubts as to whether ingesting clove oil (Syzigium aromaticum) is safe. Wolfberries (Lyceum barbarum) is a fruit from the Ningxia Province, China, where some people have lived to over 120 years.

The ORAC is not the ultimate unit, however, as different antioxidants have different effects. Lycopene protects against prostate cancer and is found in tomatoes, strawberries and pink grapefruit. Lycopene is the predominate carotenoid in plasma, and various tissues including the prostate gland (Lucich, 2001). Research (ref.) has shown spinach to be more effective than strawberries (which score higher in the ORAC assay) when measured as blood antioxidant scores. The researchers conjecture that it may be due to specific compounds or a specific combination of them in the greens. Spinach caused the biggest change in a test between spinach, strawberries, and red wine (all high-ORAC foods) and 1,250 milligrams of vitamin C.

Other essential oils are also strong antioxidants with a high ORAC value:

Sandalwood (Santalum Album)  1,655 Roman Chamomile (Chamaemelum nobile) 2,446 Juniper (Juniperus osteosperma)  2,517  Rosemary (Rosmarinus officinalis)  3,309 Lavender (Lavendula angustifolia)  3,669 Spearmint (Mentha spicata)  5,398 Helichrysum (Helichrysum italicum) 17,420  Lemongrass (Cymbopogen flexuosus)  17,765 Orange (Citrus aurantium) 18,898 Eucalyptus (Eucalyptus globulus) 24,157  Rose of Sharon (Cistus ladanifer)  38,648  Cinnamon Bark (Cinnamamum verum)  103,448 Mountain Savory (Satureja montana)  113,071 Oregano (Origanum compactum) 153,007  Thyme (Thymus vulgaris) 159,590  Clove (Syzigium aromaticum)  10,786,875

Essential oils really potent antioxidants. A drop of Clove oil contains 400 times more antioxidant per unit volume than wolfberries, the most powerful of all know fruits.

Other antioxidant measurement units

Three assays metnods for the determination of total antioxidant capacity are found in published literature: the oxygen radical absorbance capacity (ORAC) assay, the Randox Trolox-equivalent antioxidant capacity (Randox-TEAC) assay, and the ferric reducing ability (FRAP) assay (Cao & Pior, 2002). The FRAP assay is simple and inexpensive but does not measure the SH-group-containing antioxidants. The ORAC assay has high specificity and responds to numerous antioxidants. The ORAC method is chemically more relevant to chain-breaking antioxidants activity, while the FRAP has some drawbacks such as interference, reaction kinetics, and quantitation methods. On the basis of the ORAC results, green pepper, spinach, purple onion, broccoli, beet, and cauliflower are the leading sources of antioxidant activities against the peroxyl radicals (Ou et al, 2002).