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Antioxidant Power of Natural Product Supplements Highly Variable

By Judy McBride
August 9, 1999

Chances are you'll get more protection from eating fresh fruits and vegetables than from taking natural product supplements claiming to be potent antioxidants. That's according to analyses of 46 commercial preparations by researchers with the Agricultural Research Service, the chief scientific agency of the U.S. Department of Agriculture.

The total antioxidant capacity of 40 berry-based supplements ranged from 16 to 3985 ORAC units--a 249-fold difference. The supplements tested included bilberry, cranberry, chokeberry and elderberry extracts. Six other antioxidant products with grape seed or pine bark extracts or pycnogenol® ranged from 16 to 8392 ORAC units--a 525-fold difference.

ORAC--short for oxygen radical absorbance capacity--measures the ability of a chemical or biological sample to disarm oxygen free radicals, which can precipitate a cascade of oxidative damage in body cells. Theory holds that such damage is behind heart disease, cancer and other diseases of aging. So antioxidant supplements are gaining popularity.

The results remind consumers that there are no industry standards for the antioxidant capacity of natural product supplements and thus little assurance of a high quality product, according to ARS chemists Ron Prior and Guohua Cao at the USDA Human Nutrition Research Center on Aging at Tufts in Boston, Mass.

Prior and Cao report their findings in the summer issue of the Journal of the American Nutraceutical Association. An abstract of the article will appear on the Web at:

The researchers point out that a single serving of fresh or freshly cooked fruits or vegetables supplies an average of 300 to 400 ORAC units. Many fruits and vegetables--such as berries, plums, oranges, leafy greens and beets--provide much higher antioxidant levels. By contrast 28 of the 40 berry extracts tested and one of the six other products wouldn't provide 300 ORAC units in a day's suggested intake.

Scientific contact: Ronald L. Prior, phone (617) 556-3311, or Guohua Cao, phone (617) 556-3141, USDA Human Nutrition Research Center on Aging at Tufts, Boston, Mass., fax (617) 556-3299,,