A study of ferretswhich metabolize beta carotene very
much like humansshows that excess beta carotene stored in the lungs
becomes oxidized into products that turn the normal control of cell division
upside down. These oxidized metabolites decreased a tumor suppressor and
increased a tumor promoter in the animals' lungs. The finding explains why very
high doses of beta carotene appeared to increase lung cancer rates among
smokers in two large intervention trials reported in 1994 and 1996. One of
those trialsthe National Cancer Institute's CARET studywas cut
short because of this increase.
By contrast, there are no reports of harmful effects from
low-dose beta carotene supplements. And populations that eat more fruits and
vegetables rich in beta carotene and other carotenoids reportedly have a lower
incidence of cancer, particularly lung cancer. The ferrets got the human
equivalent of 30 milligrams of beta carotene dailythe dose given in the
human intervention trials. The average beta carotene intake from U.S. diets is
2 to 5 mg a day. The researchers encourage getting 8 to 10 mg daily through the
diet. That means eating plenty of carrots, dark green vegetables, cantaloupe,
sweet potatoes, pumpkin, peaches, mangos or other foods rich in this orange
pigment and other carotenoidssuch as lycopene and lutein.
Normally, body cells convert some of the beta carotene into a
vitamin A-like compound, retinoic acid. Retinoic acid is reported to dampen
cell division and is currently being used to treat skin cancer and leukemia.
But an excess of beta carotene exposed to the high oxygen levels in lung
cellsalong with the oxidizing effects of cigarette smokeapparently
wreaks havoc with this fine- tuned system. In the ferrets, the oxidized beta
carotene metabolites destroyed retinoic acid, thereby decreasing its
tumor-suppressing activity. At the same time, they turned up the volume on a
protein that activates cell division, promoting precancerous lesions, the
researchers reported in the Journal of the National Cancer Institute
(vol. 91, pp. 60-66).
Each day for six months, one group of ferrets was given the beta
carotene supplements and exposed to cigarette smokeequivalent to a person
smoking 1.5 packs a day. Two other groups got either the supplement or smoke
exposure for the same length of time, while a control group got neither. The
group getting both treatments had the strongest precancerous changes. The
products of genes that promote cell division were three- to fourfold higher in
these animals than in the control group.
For more information, contact
Robert Russell, (617) 556-3335, or
Xiang-Dong Wang, (617) 556-3130,
Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Back to Contents
In May 1997, a 3-year-old boy in Hong Kong died of the flu and
the world held its breath. Soon, this tragedy would spark new scientific
collaboration thousands of miles away at an ARS poultry research lab in Athens,
Georgia. What was so disturbing about the boy's death was that the culprit
virus had previously attacked only birdspoultry in particular. Why had
the "bird flu" changed hosts?
Understanding how and why influenza viruses mutate is critical
to avoiding disasters like the Spanish Influenza. In 1918 and 1919, the Spanish
flu killed nearly 22 million people in North America, Europe and Asia.
Similarly, Hong Kong and China have been starting points for world pandemics.
Fortunately, the 1997 "bird flu" known as H5N1 never came close to causing a
pandemic. But the episode became an important test of how the world will
respond to the next worldwide attack of avian influenza.
When the boy died in 1997, scientists at an ARS poultry research
lab in Athens, Georgia, already had a working H5 influenza vaccine for birds.
They had been studying a viral strain that attacks only poultry but is related
to H5N1, the Hong Kong bird flu strain. Based on this work, the scientists and
industry cooperators provided the Hong Kong government with the poultry
vaccine. The ARS scientists also provided the Centers for Disease Control and
Prevention with a temporary research facility. They worked extensively with CDC
to identify the virus and understand its frightening changes. A report of this
joint research appears in the Journal of Virology (vol. 72, pp.
6678-6688).
For more information, contact
David Swayne, (706) 546-3433,
Southeast
Poultry Research Laboratory, Athens, GA
Back to Contents
A new device from ARS research clears disease-causing organisms
from the air in poultry houses, protecting chicks the moment they hatch.
Airborne particles often give Salmonella bacteria a free ride to chicks'
feathers and lungs. One infected chick can quickly spread the bacteria
throughout an entire hatching cabinet. That increases the risk of
Salmonella for consumers as adult birds are grown for food.
The ARS researchers recently applied for a patent on their
system that uses a negative electrostatic charge to collect dust particles in
hatching cabinets. The system charges airborne dust and deposits it onto plates
that are automatically rinsed several times an hour. In laboratory tests, it
reduced Salmonella by 95 percent in week-old birds and in egg-laying hens.
Similar results were gotten in commercial hatching cabinets where hatchability
was improved an average of 2.7 percent, the researchers reported in the
Journal of Applied Engineering in Agriculture (vol. 14, pp. 551-555). In
other experiments with Salmonella-infected chicks, it reduced airborne
transmission by 99 percent. But the system may offer even more protection:
preliminary tests with the laying hens seem to show the charge kills bacteria
outright.
For more information, contact
Bailey Mitchell, (706) 546-3443,
Southeast
Poultry Research Laboratory, Athens, GA;
Back to Contents
A simple three-step process can help poultry producers keep
Salmonella and other food pathogens out of poultryand may increase
profits. It all begins with the egg, according to ARS scientists. The steps
involve cleaning the eggs, treating chicks with a safe spray and using
beneficial microbes to protect growing birds.
First, farmers spray freshly laid eggs with a mild detergent and
a reliable farm disinfectant chemical. This lowers surface contamination from
bacteria. Next, hatcheries spray a fine mist of hydrogen peroxide or other
effective chemical in the cabinet while chicks are hatching. This protects the
newly hatched chicks from airborne Salmonella. And last, in the grow-out house,
workers give benign gut bacteria from healthy mature chickens to young chicks
to prevent colonization by Salmonella. Even if chicks come in contact with
Salmonella, they will not become carriers.
The researchers confirmed the effectiveness of the first step
with a producer, which is reported in the Journal of Applied Poultry
(vol. 6, pp. 298-305). This producer found cleaning and disinfecting eggs paid
for itself because more of the eggs could be sold at a higher price. A dozen
clean hatching eggs sell for about 30 cents. A soiled dozen sell for only about
7 cents for use in pasteurized egg products. ARS scientists estimate that a
large-scale farm selling millions of eggs annually could recover the cost of
the spraying equipment in two years.
For more information, contact
Mark Berrang, (706) 546-3551,
Richard B. Russell Agricultural
Research Center, Athens, GA
Back to Contents
There's now more evidence that cumulative oxidative damage to
brain cells causes the fuzzy memory, slow learning and loss of coordination
that often accompanies aging. Using young rats, researchers have developed a
model for the aging brain that will help them learn what counteracts the damage
to brain cells caused by naturally generated oxygen free radicals.
The researchers produced losses in cognitive and motor function
in young rats by first reducing levels of a natural antioxidant, glutathione,
in the animals' brains. Then they added the hormone dopamine, which rapidly
oxidizes, generating free radicals. By contrast, rats continued to function
like young animals when they were given extra dopamine while their antioxidant
(glutathione) levels were still high. The rat model and results of learning and
memory tests are reported in Free Radical Biology & Medicine (vol.
23, pp. 412-418, and vol. 24, pp. 1149-1158).
This further supports the case that antioxidants may prevent or
slow the loss of motor controlas well as memory and learning
abilityassociated with aging. The brain is rather deficient in natural
antioxidants, especially considering that it uses a lot of oxygen, which
generates free radicals. It also harbors high concentrations of irona
strong oxidizerand is rich in fatty acids, which are highly vulnerable to
oxidation. Studies show that antioxidant levels diminish with age. So the aging
brain appears to be an easy target for oxidative damage.
The researchers developed this young animal model because old
animals are very expensive and may have impaired visiona factor that
would confound the learning and memory test. They will use this model to test
the protective effects of antioxidant vitamins and other beneficial compounds
in plant foods, or phytonutrients, such as flavonoids. They will look for
antioxidants that cross the blood-brain barrier and compounds that stimulate
the cells to produce adequate levels of natural antioxidants.
For more information, contact
Barbara Shukitt-Hale, (617)
556-3118,
Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Back to Contents
African-American teen-age girls tend to be taller and heavier
and to mature faster than their peers in other ethnic groups. A new study
suggests one possible explanation: African-American girls in the study had
higher blood levels of leptin, a hormone that helps cue "fullness."
Manufactured in fat tissue, leptin is a biochemical cue for
curbing appetite and burning calories. It and another
hormoneneuropeptide-Y, which triggers hungerhelp control the cycle
of hunger and satiety. When blood leptin runs higher, however, the body may
require more to "hear" its biochemical message, according to the study leader.
The researchers conducted the study with 136 healthy
volunteers79 white and 57 African- American girlsall students in
the Houston, Texas, area. They ranged in age from 8 to 17 years. The findings,
published in the Journal of Clinical Endocrinology and Metabolism (vol.
83, pp. 3574-3577), help fill gaps in data on energy metabolism in the
African-American population.
Medical research has suggested that higher leptin levels may
speed sexual maturity and make the body better at conserving energy. Higher
energy efficiency could help explain why African- American girls grow faster
than peers in other ethnic groups. This metabolic efficiency can backfire in
adulthood by contributing to obesity and increased health risk. But the new
study adds further evidence that establishing healthy life styles in childhood
can have lasting beneficial effects into adulthood.
For more information, contact
William W. Wong, (713) 798-7168,
Children's Nutrition Research
Center, Houston, TX
Back to Contents
Prolina, a high-protein soybean originally bred for animal
feed, appears to have the right amino acid mix to make soy infant formula more
like mother's milk. Among Prolina's appealing qualities is an unusually high
concentration of cysteine, an amino acid that occurs naturally in human breast
milk. In fact, Prolina has several times more cysteine than regular soybean
varieties.
Humans have a higher ratio of cysteine in their breast milk than
all other mammals. Scientists have speculated that high cysteine levels promote
brain and eye development because the body uses it to make taurine, a compound
highly concentrated in these organs.
Formula manufacturers have been looking for a way to more
closely match mother's milk with a vegetable-based formula. Prolina may just be
the formula for success. Breast feeding is preferable to formula for all
infants, but sometimes this isn't possible, particularly if the infant has
trouble digesting larger proteins found in breast milk. Soy formula can be an
alternative.
Prolina soybeans are high in 11S and 7S proteins, a special
class of proteins with enhanced functional properties. This means it's easier
to process these beans into a gel form for a fat-free whipped cream made from
soy or to blend them into a liquid emulsion like infant formula, according to
an ARS chemist. He has been working with food scientists at North Carolina
State University to develop new products, such as high-protein soyburgers,
based on Prolina's properties.
For more information, contact
Prachuab Kwanyuen, (919)
515-2734, Soybean and
Nitrogen Fixation Laboratory, Raleigh, NC
Back to Contents
Of more than 50 plant foods tested in an ARS laboratory,
blueberries score among the highest in antioxidant power. And animal studies in
this laboratory suggest that eating blueberries and other high-antioxidant
fruits and vegetables may retard the oxidative damage to tissues associated
with aging. Now the researchers have found a three-fold difference in
blueberries' ability to subdue oxygen radicals, depending on species and
maturity at harvest.
Using the ORAC assay for total antioxidant capacity, they
analyzed commercial blueberry varieties and less common species from the United
States and Canada. They also analyzed the closely related bilberry from
Germany. Results are published in the Journal of Agricultural and Food
Chemistry (vol. 46, pp. 2686-2693).
Overall, the German bilberry scored highest in antioxidant
capacity. However, lowbush blueberries from Nova Scotia and some other U.S.
cultivars were quite close to the bilberry in antioxidant capacity, depending
upon their stage of maturity.
Naturally ripened blueberries not only taste better than berries
picked before their prime, they may be more healthful than fruits picked early
for long shipments. Mature berries from two commercial rabbiteye
cultivarsBrightwell and Tifbluescored one and one-half to more than
twice as high as berries picked seven weeks earlier from the same bush. That's
due to the increase in antioxidant pigments, or anthocyanins, as the berries
mature.
Region did not affect the antioxidant score, based on analyses
of berries from the northern highbush variety, Jersey, grown in Oregon,
Michigan and New Jersey.
For more information, contact
Ronald L. Prior or
Guohua Cao, (617) 556-3310,
Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston,
MA
Back to Contents
Next to water, tea is the most consumed beverage worldwide. And
it's one of a few food products known to contain significant levels of potent
antioxidants known as catechins. So ARS scientists recently measured catechins
in various black tea products, including bags, instant iced tea mixes, bottled
and herbal teas. Catechins (pronounced CAT-eh-kins) belong to a loosely knit
family, known as the flavonoids, which have been noted for their antioxidant
activity.
Teas brewed from bags had the highest catechin content along
with the highest caffeine content. However, there was a twofold difference in
catechin content among the 12 black teas tested. It ranged from 122 micrograms
per milliliter (ug/ml) for a brewed decaffeinated tea to 250 ug/ml for a brewed
regular tea. Decaffeinated teas had lower levels of catechins. The highest
levels are equivalent to the levels in green tea, which has been touted for its
health-giving properties.
Instant (powdered) tea mixes, on the other hand, had little or
no catechinswith a couple of exceptions. Bottled and herbal teas had
none. These analyses were part of a larger effort in ARS' Food Composition
Laboratory to compile information on health-enhancing phytonutrients in foods.
For more information, contact
Gary Beecher, (301) 504-8356,
Beltsville Human
Nutrition Research Center, Beltsville, MD 20705
Back to Contents
Fresh tomatoes, tomato sauces and juices promise to have much
more beta carotene, thanks to new tomato breeding lines developed by an ARS
scientist. Three of the linesfor use in processing into paste, juices and
saucescontain about 10 to 25 times more beta carotene than typical
tomatoes. They have already been released to interested breeders.
High beta-carotene cherry and beefsteak type tomatoes will also
be released as specialty tomatoes for the fresh market. The United States is
number two in fresh and processed tomato production worldwide, with Florida and
California the top producing states.
Consumers soon may be able to get plenty of beta-carotene from
eating pizza, spaghetti and other tomato-based dishes. A major food producer is
already using the material derived from the ARS germplasm to develop
nutritionally enhanced products. The human body converts beta carotene into
vitamin A and other important compounds, such as tumor suppressing retinoic
acid.
For more information, contact
John Stommel, (301) 504-5583,
Vegetable Laboratory,
Beltsville, MD
Back to Contents
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.
Comments? |