Research results 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.
Foods that score high in an antioxidant analysis called ORAC may protect cells and their components from oxidative damage, according to ORAC studies of animals and human blood at the USDA Agricultural Research Service's Human Nutrition Research Center on Aging at Tufts University 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.
"If these ORAC 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. By the year 2050, nearly one-third of the U.S. population is expected to be over age 65. If further research supports these early findings, millions of aging people may be able to guard against diseases or dementia simply by adding high-ORAC foods to their diets.
High-ORAC foods raised the antioxidant power of human blood 10 to 25 percent. High-ORAC foods prevented some loss of long-term memory and learning ability in middle-aged rats. High-ORAC foods maintained the ability of brain cells in middle-aged rats to respond to a chemical stimulus--a function that normally decreases with age. High-ORAC foods 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.
Drs Cao 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. They tested red wine because it has a high ORAC value - higher than white wine - and has been associated with a lower risk of cardiovascular disease
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 high ORAC 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 high-ORAC blueberry extract.
Neuroscientist James Joseph and psychologist Barbara Shukitt-Hale at the center tested middle-aged rats that had eaten diets fortified with high-ORAC 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."
Based on the evidence so far, Drs. Prior and Cao suggest that daily intake be increased to between 3,000 and 5,000 ORAC units to have a significant impact on plasma and tissue antioxidant capacity.
The antioxidant capacity of the blood seems to be tightly regulated, he says. Still, "a significant increase in antioxidants of 15 to 20 percent is possible by increasing consumption of fruits and vegetables, particularly those high in ORAC value."
The ORAC values of fruits and vegetables cover such a broad range, he adds, "you can pick seven servings with low ORAC values and get only about 1,300 ORAC units. Or, you can eat seven servings with high ORAC values and reach 6,000 ORAC units or more. One cup of blueberries alone supplies 3,200 ORAC units."
ORAC units per 100 grams (about 3½ ounces)
|
Fruits |
ORAC |
Vegetables |
ORAC | |
|---|---|---|---|---|
| Prunes |
5570 |
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 |
Egg plant |
390 | |
| Kiwi fruit |
602 |
|||
| Grapefruit, pink |
483 |
|||
By Judy McBride, Agricultural Research Service Information Staff. This research is part of Human Nutrition Requirements, Food Composition, and Intake, an ARS National Program.
Reprinted with permission of the USDA.
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.
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