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Foods that score high in an antioxidant assay called ORAC may protect
cells and their components from damage by oxygen radicals, according
to studies of animals and human blood. ORAC measures the total antioxidant
power of foods and other chemical substances. Early findings suggest
that eating plenty of high-ORAC fruits and vegetablessuch as spinach
and blueberriesmay help slow the processes associated with aging
in both body and brain.
Two human studies show that eating high-ORAC fruits and vegetables
or simply doubling intake of fruits and vegetablesboth naturally
high in antioxidantsraises the antioxidant power of the blood
between 13 and 25 percent. The studies are published in the Journal
of Nutrition (vol. 128, pp. 2383-2390) and the American Journal of
Clinical Nutrition (vol. 68, pp. 1081-1087).
Early evidence for the protective power of high-ORAC foods comes from
rat studies. Rats fed daily doses of blueberry extract for six weeks
before being subjected to pure oxygen suffered much less damage to the
capillaries in and around their lungs. In other tests, middle-aged rats
were fed 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 15-month-old
rats. Spinach also proved most potent in protecting different types
of nerve cells in two separate parts of the brain against the effects
of aging, the researchers reported in the Journal of Neuroscience
(vol. 18, pp. 8047-8055).
For more information, contact Ronald Prior or James
Joseph, (617) 556-3310, Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston,
MA
Top Antioxidant Foods
[ORAC* units per 100 grams**]
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Fruits
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Vegetables
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Prunes |
5770 |
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Kale |
1770 |
Raisins |
2830 |
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Spinach |
1260 |
Blueberries |
2400 |
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Brussels sprouts |
980 |
Blackberries |
2036 |
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Alfalfa sprouts |
930 |
Strawberries |
1540 |
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Broccoli florets |
890 |
Raspberries |
1220 |
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Beets |
840 |
Plums |
949 |
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Red bell peppers |
710 |
Oranges |
750 |
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Onions |
450 |
Red grapes |
739 |
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Corn |
400 |
Cherries |
670 |
|
Eggplant |
390 |
* Oxygen Radical Absorbance Capacity |
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**About 3.5 ounces |
Back to Contents
Ever wonder why you feel hungry a few hours after eating a big meal?
Chances are you ate carbohydrate-containing foods that caused a rapid
spike in your blood sugar. This musters extra insulin into the blood.
The high insulin, in turn, makes blood sugar crash and suppresses the
fat fuels as well. As a result, you get that famished feeling that leads
to overeating.
That's what happened in a study of obese teenage boys by researchers
at Children's Hospital in Boston and the USDA center in Boston. It's
the first solid evidence that carbohydrates with a high glycemic index
(GI)those that are rapidly digested and absorbedcontribute
to obesity.
On three separate days at least a week apart, researchers fed the boys
breakfast and lunch having either a high, medium or low glycemic index.
The boys ate almost twice as much after the high-GI meals compared to
the low-GI fare. The high-GI meals induced a sequence of hormonal and
metabolic changes that promoted overeating, the researchers reported
in the electronic edition of Pediatrics at: http://www.pediatrics.org/cgi/content/full/103/3/e26.
They suspect the findings apply to the middle-aged and elderly as well.
About one-fifth of U.S. children and one-third of adults are now significantly
overweight, despite a significant drop in fat intake over recent years.
Most starchy foods commonly eaten in North America, chiefly refined
grain products and potatoes, have a high GI. Moreover, many of the low-fat
foods that have flooded grocery shelves are also high in calories. Some
starchy foods have GI's up to 50 percent higher than table sugar. Sources
of concentrated sugars, such as sodas and fruit juices, also have a
high GI. By contrast, vegetables, legumes and fruits generally have
a low GI.
For more information, contact Susan B. Roberts, (617) 556-3238,
Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts, Boston, MA , or David
S. Ludwig, (617) 355-4878, Children's Hospital, Boston, MA
Back to Contents
Taxol, a powerful but expensive anti-cancer drug, could become more
plentiful in the future. Researchers have vastly improved the process
for producing taxol in cell culture. The new process is 100 times more
productive than the original cell-culture technique patented by ARS
in 1991. Taxol is a potent chemotherapy drug for breast, ovarian, lung
and other cancers. But it takes about 6,700 pounds of bark from increasingly
scarce Pacific yew trees to produce a pound of the taxol drug.
Researchers with ARS, Washington State University and Cornell Research
Foundation, Inc., screened some 2,000 cell lines from all five known
yew species and found about 20 that are good taxol producers. They also
optimized the growth media and other culture conditions for these top
producers, they report in Biotechnology and Bioengineering (vol.
62, pp. 97-105). Their efforts increased taxol output from about 1 milligram
per liter to more than 100 mg/L. The cultures also produce some taxol-related
compounds, called taxanes, that can be converted to the drug in a semi-synthetic
process.
ARS has applied for patent protection on the new process. If use of
this new source of taxol is approved by the U.S. Food and Drug Administration
and proves medically effective, anti-cancer drugs based on the process
could be available within a few years.
For more information, contact Donna
M. Gibson, (607) 255-2359, U.S.
Plant, Soil and Nutrition Research Laboratory, Ithaca, NY
Back to Contents
Now there's a technique to rapidly detect DT104, a potentially deadly
strain of Salmonella bacteria that resists many antibiotics. ARS researchers
found a key gene sequence, present in this virulent strain of Salmonella
typhimurium, that allows for quick identification. The new technique
cuts identification time from six weeks to two hours. It means scientists
can take samples, grow a culture, identify Salmonella DT104 and begin
treatment in three to five days.
The sooner physicians know that they are dealing with DT104, the sooner
they can begin the treatments needed to combat the bacteria. Delays
in identifying DT104 almost cost a Vermont dairy farmer her life in
1997 and killed 14 of her cows. The pathogen has killed people in Great
Britain and sickened children in Nebraska.
The new technique opens the door to development of test kits. Such
a kit might be able to detect the pathogen in blood samples or in runoff
water from animal production.
For more information, contact Paula
Fedorka-Cray, (706) 546-3305, Poultry
Microbiological Safety Research Unit, Athens, GA
Back to Contents
Some people love putting a dollop of horseradish on their steamy roast
beef. As it turns out, this natural taste-maker may also be a useful
food preservative. ARS studies show that both horseradish and mustard
oil pack a punch against Listeria monocytogenes, E. coli,
Staphylococcus aureus and other food pathogens you definitely
don't want in your sandwich.
That's because these condiments contain a pungent chemical with the
unsavory name of allyl isothiocyanate (AITC). Mustard oil is 93 percent
AITC but has a milder flavor than horseradish, which is 60 percent AITC,
researchers reported in the Journal of Food Science (vol. 63,
pp. 621-624).
In 1989, USDA issued a "zero tolerance" policy for L.
monocytogenes. But consumers now demand that foods rely less on
artificial preservatives. This research fits in with the trend of seeking
natural substitutes for chemical preservatives in the food industry.
If this work is borne out in further research, horseradish and mustard
oil could join the natural arsenal against malevolent microbes.
For more information, contact Henry Fleming, (919) 515-2979, Food
Science Research Unit, Raleigh, NC, or Brian Shofran, (405) 744-4115, Oklahoma
State University, Stillwater, OK ;
Back to Contents
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Recognizing that the elderly need fewer calories than
younger Americans, researchers have modified USDA's Food Guide Pyramid
for the over-70 generation, hoping to optimize their nutrient intake.
Published in the Journal of Nutrition (vol. 129, pp. 751-753),
the modified pyramid emphasizes nutrient- dense foods, fiber and water
and recognizes a possible need for supplements. Its base is narrower
than the original pyramid to reflect the decrease in energy (calorie)
needs. And it rests on a new base accenting the elderly's need for fluidsat
least 2 quarts, or 8 cups, of water per day. Older people often have
a reduced sense of thirst, and that can lead to dehydration.
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A fiber icon is scattered throughout to emphasize the need for a high-fiber
diet. The food groups and recommended servings are the same as in the
original pyramid with more emphasis on nutrient density and fiber. The
researchers recommend that elderly consumers choose foods from the bread
and cereal group that are whole-grain, enriched or fortified. Preferred
vegetables are dark green, orange or yellow, which contribute vitamin
C, vitamin A and folic acid, and the crucifers, such as beets, kale,
cabbage and broccoliall rich in antioxidants. Fruits should be
yellow, orange or red, and the whole food is preferable to fruit juice.
The researchers also recommend that dairy products be low fat.
A flag at the top of the pyramid reminds older people that they may
need to add supplements of calcium, vitamin D and vitamin B12 to bring
daily intakes up to recommended levels. Those who exclude dairy products
because of lactose intolerance, for instance, may need extra calcium.
If sun exposure is minimal, a vitamin D supplement might be in order.
And a vitamin B12 supplement may be necessary because many elderly don't
efficiently absorb the vitamin from meat and other foods.
For more information, contact Robert M. Russell, (617) 556-3133, or
Alice H. Lichtenstein,
(617) 556- 3127, Jean Mayer USDA
Human Nutrition Research Center on Aging at Tufts, Boston, MA
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Irradiating bagged salads after washing the vegetables in a chlorine
solution reduces harmful and harmless microorganisms without affecting
quality, studies show. And the irradiated lettuce has about the same
shelf life as untreated samples. That's good news for health-conscious
consumers who are eating more salads. U.S. sales of packaged lettuce
alone were more than $1.2 billion in 1997.
A chlorine wash doesn't eliminate all the organisms that can be present
on fresh-cut lettuce, like Shigella and E. coli O157:H7. This combination
treatment could help fresh-cut salads to be included in diets of people
with weakened immune systems who otherwise can't enjoy them.
Irradiation significantly reduced the microbial and yeast populations.
Eight days after zapping chlorine-washed lettuce with only 0.2 kilogray
(kGy) of irradiation, microbial counts were 290 colony-forming units
(CFU) and 60 CFU of yeast. That's compared to counts of 220,000 CFU
and 1,400 CFU of yeast on nonirradiated lettuce, the researchers published
in the Journal of Agricultural and Food Chemistry (vol. 45, pp.
2864-2868). The U.S. Food and Drug Administration has approved up to
1 kGy of irradiation for fresh produce.
Scientists also irradiated chlorine-washed, shredded carrots in modified-atmosphere
packaging. Nine days after irradiation, on the expiration date, microbial
count was 1,300, compared with 87,000 for nonirradiated, chlorinated
control samples, as reported in the Journal of Food Science (vol.
65, pp. 162-164).
For more information, contact Robert
D. Hagenmaier, (941) 293-4133, x123, U.S.
Citrus and Subtropical Products Research Laboratory, Winter Haven,
FL
Back to Contents
A profile of U.S. blood homocysteine levels confirms findings of earlier,
nonrepresentative studies: This recently recognized risk factor for
heart disease increases with age and is higher in males than females.
Homocysteine is produced during the conversion of one amino acid into
another. Incomplete conversion causes a buildup of homocysteine in the
blood where it is thought to irritate artery linings, encouraging formation
of plaquefatty deposits that cling to artery walls.
Researchers with the USDA center in Boston used sera from the latest
National Health and Nutrition Examination Survey to measure homocysteine
for 3,766 males and 4,819 females from age 12 up. Homocysteine levels
between the two genders were closest in the young and old, diverging
around puberty and converging after menopause. Researchers with the
Centers for Disease Control and Prevention collaborated on the study,
published in the American Journal of Clinical Nutrition (vol.
69, pp. 482-489).
One unexpected finding: Mexican-American females had the lowest homocysteine
levels. The researchers don't have an explanation for this finding yet.
As for higher homocysteine levels in older people, they suspect impaired
kidney function may contribute. And the difference between genders may
be due to body size, estrogen and vitamin status.
Low intake of folate, vitamin B12 or vitamin B6 can be a cause for
the homocysteine buildup. Orange juice and green leafy vegetables are
good sources of folate, which seems the most limiting of the three vitamins.
For more information, contact Paul
Jacques (617) 556-3322, Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston,
MA
Back to Contents
A consortium called the Delta Nutrition Intervention Research Initiative
promises to help low-income families of the lower Mississippi Delta
eat better food and lead healthier lives. Delta NIRI involves poor Delta
communities in deciding what their key nutrition problems are and empowers
them to find solutions, with help from nutrition scientists.
Compared to national statistics, Delta families are more likely to
lack prenatal care, have low-birth-weight newborns and high infant mortality.
Nutrition-related chronic diseases such as hypertension, cardiovascular
disease and diabetes are also above national averages.
Coordinated by ARS, Delta NIRI serves 36 counties or parishes in Louisiana,
Mississippi and Arkansas. Its members include seven nutritional research
centers in those states. Begun in 1995, Delta NIRI has an operating
budget of $3.1 million for 1999. The consortium hires and trains Delta
residents to survey area counties about health and nutrition problems.
Then researchers in the Delta NIRI program design and test nutrition
interventions based on these concerns. Ultimately, the community decides
if the programs are worthwhile and should continue.
For more information, contact Margaret L. Bogle, (501) 954-9152,
ARS Delta Nutrition
Intervention Research Initiative, Little Rock, AR
Back to Contents
Getting enough copper during pregnancy may be important for Baby's
brain development, according to a study of newborn rat pups. Slashing
the mother rats' copper intake during pregnancy and nursing reduced
the pups' brain levels of the enzyme PKC, important to development of
the nervous system. The findings may have implications for people in
the U.S. and other industrialized nations where copper intake is less
than desirable.
Throughout pregnancy and afterward, one group of rat mothers got only
1 microgram (mcg) of copper dailyone-sixth the level recommended
for pregnant rats. A second group got 2 mcg and a control group got
all they needed. PKC increased in all the pups' brains during the three
weeks after birth. But compared to the control group, the increase was
only about half as much in the group whose moms got 1 mcg of copper.
Pups from the 2-mcg group also had a smaller increase25 percent
less overallwith one form of PKC lagging by 50 percent in the
cerebellum, which controls motor function. This is significant because
poor muscle coordination is a well-known symptom of copper deficiency
in baby animals.
The brain has several enzymes that would suffer from a shortage of
copper. Some contain copper. Others, like PKC don't contain it but are
less active in its absence. Between 1.5 and 3 milligrams of copper daily
is currently suggested for all adults. The richest sources of copper
are oysters, liver and cocoa. Whole grains, nuts and seeds are good
sources.
For more information, contact W.
Thomas Johnson, (701) 795-8411, Grand
Forks Human Nutrition Research Center, Grand Forks, ND
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The United States Department of Agriculture (USDA)
prohibits discrimination in all its programs and activities on the basis of
race, color, national origin, gender, religion, age, disability, political
beliefs, sexual orientation, and marital or family status. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative
means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at 202-720-2600 (voice and
TDD). To file a complaint of discrimination, write USDA, Director, Office of
Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue, SW,
Washington, DC 20250-9410 or call 202-720-5964 (voice or TDD). USDA is an equal
opportunity provider and employer.
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