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High-ORAC Foods May Slow Aging / February 8, 1999 / News from the USDA Agricultural Research Service

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High-ORAC Foods May Slow Aging

By Judy McBride
February 8, 1999

WASHINGTON, Feb. 8--Foods that score high in an antioxidant analysis called ORAC may protect cells and their components from oxidative damage, according to studies of animals and human blood at the Agricultural Research Service's Human Nutrition Research Center on Aging at Tufts in Boston. ARS is the chief scientific agency of the U.S. Department of Agriculture

ORAC, short for Oxygen Radical Absorbance Capacity, is a test tube analysis that measures the total antioxidant power of foods and other chemical substances.

Early findings suggest that eating plenty of high-ORAC fruits and vegetables--such as spinach and blueberries--may help slow the processes associated with aging in both body and brain.

"If these findings are borne out in further research, young and middle-aged people may be able to reduce risk of diseases of aging--including senility--simply by adding high-ORAC foods to their diets," said ARS Administrator Floyd P. Horn.

In the studies, eating plenty of high-ORAC foods:

  • Raised the antioxidant power of human blood 10 to 25 percent
  • Prevented some loss of long-term memory and learning ability in middle-aged rats
  • Maintained the ability of brain cells in middle-aged rats to respond to a chemical stimulus--a function that normally decreases with age
  • Protected rats' tiny blood vessels--capillaries--against oxygen damage

Nutritionist Ronald L. Prior contends, "If we can show some relationship between ORAC intake and health outcome in people, I think we may reach a point where the ORAC value will become a new standard for good antioxidant protection." (See table at end for ORAC values of fruits and vegetables.)

The thesis that oxidative damage culminates in many of the maladies of aging is well accepted in the health community. The evidence has spurred skyrocketing sales of antioxidant vitamins. But several large trials have had mixed results.

"It may be that combinations of nutrients found in foods have greater protective effects than each nutrient taken alone," said Guohua (Howard) Cao, a physician and chemist who developed the ORAC assay.

He and Prior have seen the ORAC value of human blood rise in two studies. In the first, eight women gave blood after separately ingesting spinach, strawberries and red wine--all high-ORAC foods--or taking 1,250 milligrams of vitamin C. A large serving of fresh spinach produced the biggest rise in the women's blood antioxidant scores--up to 25 percent--followed by vitamin C, strawberries and lastly, red wine

In the second study, men and women had a 13- to 15-percent increase in the antioxidant power of their blood after doubling their daily fruit and vegetable intake compared to what they consumed before the study. Just doubling intake, without regard to ORAC scores of the fruits and vegetables, more than doubled the number of ORAC units the volunteers consumed, said Prior.

Early evidence for the protecting power of these diets comes from rat studies by Prior, Cao and colleagues. Rats fed daily doses of blueberry extract for six weeks before being subjected to two days of pure oxygen apparently suffered much less damage to the capillaries in and around their lungs, Prior said. The fluid that normally accumulates in the pleural cavity surrounding the lungs was much lower compared to the group that didn't get blueberry extract.

Neuroscientist James Joseph and psychologist Barbara Shukitt-Hale at the center tested middle-aged rats that had eaten diets fortified with spinach or strawberry extract or vitamin E for nine months. A daily dose of spinach extract "prevented some loss of long-term memory and learning ability normally experienced by the 15-month-old rats," said Shukitt-Hale.

Spinach was also the most potent in protecting different types of nerve cells in two separate parts of the brain against the effects of aging, said Joseph.

"These cells were significantly more responsive when the animals ate diets fortified with high-ORAC foods--especially spinach--compared to unfortified diets," Joseph said. "The spinach group scored twice as responsive as the control animals."

Why spinach is more effective than strawberries--which score higher in the ORAC assay--is still a mystery. The researchers conjecture that it may be due to specific compounds or a specific combination of them in the greens.

More details on this research appear in an article in the February issue of Agricultural Research, ARS' monthly magazine. The story is also available on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/feb99/aging0299.htm


Top-Scoring Fruits & Vegetables
ORAC units per 100 grams (about 3 ½ ounces)
Fruits Vegetables
Prunes 5770 Kale 1770
Raisins 2830 Spinach 1260
Blueberries 2400 Brussels sprouts 980
Blackberries 2036 Alfalfa sprouts 930
Strawberries 1540 Broccoli flowers 890
Raspberries 1220 Beets 840
Plums 949 Red bell pepper 710
Oranges 750 Onion 450
Red grapes 739 Corn 400
Cherries 670 Eggplant 390
Kiwi fruit 602
Grapefruit, pink 483

Scientific contact: Ronald Prior, James Joseph, Guohua Cao or Barbara Shukitt-Hale, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, Mass., phone (617) 557-3310, fax (617) 556-3299, prior@hnrc.tufts.edu; joseph_ne@hnrc.tufts.edu; cao_am@hnrc.tufts.edu; hale_ne@hnrc.tufts.edu.

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