High ORAC Foods May Slow Aging

High-ORACFoods May Slow Aging

ByJudy McBride
February 8, 1999

USDAARS

WASHINGTON, Feb. 8--Foods that score high in an antioxidantanalysis called ORAC may protect cells and their components from oxidativedamage, according to studies of animals and human blood at the AgriculturalResearch Service's Human Nutrition Research Center on Aging at Tufts in Boston. ARSis the chief scientific agency of the U.S. Departmentof Agriculture.

ORAC, short for Oxygen Radical Absorbance Capacity, is a test tubeanalysis that measures the total antioxidant power of foods and other chemicalsubstances.

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

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

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

* Raised the antioxidant power of humanblood 10 to 25 percent

* Prevented some loss of long-term memoryand learning ability in middle-aged rats

* Maintained the ability of brain cells inmiddle-aged rats to respond to a chemical stimulus--a function that normallydecreases with age

* Protected rats' tiny bloodvessels--capillaries--against oxygen damage

Nutritionist Ronald L. Prior contends, "If we can show somerelationship between ORAC intake and health outcome in people, I think we mayreach a point where the ORAC value will become a new standard for goodantioxidant protection." (See table at end for ORAC values of fruits andvegetables.)

The thesis that oxidative damage culminates in many of the maladiesof aging is well accepted in the health community. The evidence has spurredskyrocketing sales of antioxidant vitamins. But several large trials have hadmixed results.

"It may be that combinations of nutrients found in foods havegreater 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 twostudies. In the first, eight women gave blood after separately ingestingspinach, strawberries and red wine--all high-ORAC foods--or taking 1,250milligrams of vitamin C. A large serving of fresh spinach produced the biggestrise in the women's blood antioxidant scores--up to 25 percent--followed byvitamin C, strawberries and lastly, red wine.

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

Early evidence for the protecting power of these diets comes fromrat studies by Prior, Cao and colleagues. Rats fed daily doses of blueberryextract for six weeks before being subjected to two days of pure oxygenapparently suffered much less damage to the capillaries in and around theirlungs, Prior said. The fluid that normally accumulates in the pleural cavitysurrounding the lungs was much lower compared to the group that didn't getblueberry extract.

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

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

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

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

More details on this research appear in an article in the Februaryissue of Agricultural Research, ARS'monthly magazine.

 

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.