A generation of "TV-dinner" kids
might be learning their eating habits from Homer Simpson, according to a
one-week survey of 287 fourth-, fifth- and sixth-graders in the Houston area.
More than 42 percent of the dinners they ate at home were consumed while
watching television. Overweight children in the survey reported eating 50
percent of their dinner meals in front of the television, compared to just 35
percent by normal-weight children.
African-American and
Mexican-American children--two groups known to be at-risk for weight
problems--reported the greatest number of dinner meals eaten while watching
television: 62 and 43 percent, respectively. Asian-American children reported
the fewest--21 percent--while Euro-American kids reported eating 32 percent of
their dinner meals while watching television.
The researcher--a behavioral
nutritionist--finds this troubling because family meals are important for
children, from both a nutritional and a developmental standpoint. There's a
known association between the number of hours children spend watching
television and weight problems. Those who watch television while eating also
tend to be unaware of how much they eat, which encourages overeating. And
studies show children tend to request food products that are more frequently
advertised on television--most of which are low in nutritional value.
What's more, food commercials often
suggest the use of food for purposes like fun or "image" rather than to satisfy
hunger or be healthy, and seldom show how the advertised food fits into a
healthy diet. By contrast, research suggests that children who eat dinner with
their parents tend to eat healthier, consuming less saturated fat and more of
several important nutrients than their unsupervised peers. Positive family
mealtime conversations can also build children's self-esteem and foster
positive relationships that help children and parents talk through tough issues
when they arise.
For more information, contact
Karen W. Cullen, (713) 798-7000,
Children's Nutrition Research Center at
Baylor College of Medicine, Houston, TX
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Parents who tightly control what
their children eat actually might be promoting a preference for off-limit foods
and a less-than-healthy relationship with food. A recent study showed that
daughters of parents with the most restrictive food practices were more likely
to overeat when left free to chose tasty snacks than those whose parents had a
more relaxed approach. And the more a child felt restricted, the more negative
feelings she expressed about having eaten snacks.
The researcher studied nearly 200
5-year-old European-American girls and their parents to determine whether
restrictive child feeding practices affect the way children learn to evaluate
their own eating behavior. First, she measured parental restriction by
determining how much access each parent typically gave their child to the 10
snack foods used in the study. Children's perception of parental restriction
was also assessed and scored.
Next, each child was given a
filling lunch and was then left alone for 10 minutes in an observation room
with toys and large bowls of 10 desirable snacks--including chocolate bars,
potato chips, ice cream and fruit candies. Afterwards, the researcher asked
each child if the amount of snack foods she'd eaten was too little, just
enough, or too much and how she felt about her snack eating. She also measured
each child's actual consumption.
In the absence of hunger, the girls
ate an average of 123 calories in snack foods. Roughly half reported eating
"too much" and feeling bad about eating at least one or more of the snack
foods. Approximately one-third said that they would feel bad if their mother or
father found out about what they had eaten. The girls' negative evaluations
reflected their perception that their parents restricted these snacks rather
than how much they actually ate. The more restriction felt, the more a child
tended to eat, the researcher reported in the Journal of the American
Dietetic Association, 2000 (vol 100, pp. 1341-1346).
She concludes that, while parents
should be responsible for deciding what types of foods are appropriate to bring
home, allowing children to be active participants in their own eating decisions
is equally important. A less restrictive approach, which includes high-fat,
high-sugar foods as part of a well-varied diet, could be better for helping
young girls stay in touch with their own fullness cues and maintain a healthy
view of their own eating.
For more information, contact
Jennifer Fisher, (713) 798-7000,
Children's Nutrition Research Center at
Baylor College of Medicine, Houston, TX
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A comprehensive new study might
allay any lingering debate about why metabolism slows as people age. The
findings show that the gradual loss of body cells, especially those
high-energy- consuming muscle cells, can help explain why older people burn
fewer calories while at rest-- which so often leads to creeping weight gain.
Some scientists have suggested that
changes in hormones, immune function or other factors may depress resting
metabolism with aging. But this study---published in the Journal of
Gerontology: Medical Sciences, 2000 (vol. 55A, pp. M757-760)--showed a
direct association between metabolic rate and cell mass, also known as lean- or
fat-free mass. And that means that older people may regain some of their
youthful resting metabolic rate and get off the slow boat to obesity by regular
muscle-building exercises. Increasing muscle mass would help seniors, according
to the researchers.
They analyzed measurements of body
composition and resting metabolic rate for 131 healthy men and women taken over
a five-year period at the Boston center. The subjects ranged in age from 18 to
87, giving the researchers a broad sample for detecting small changes in cell
mass across the years. But they found that only one of the six methods used to
measure the subjects' body composition exposed the decline in cell mass
occurring with age. That was a high-tech method for measuring the body's total
potassium--a mineral found almost entirely inside of cells.
Related studies at the center
further support an age-related loss of cell mass. Researchers found a definite
decline in muscle mass of middle-aged and senior men and women over 10- and
12-year periods when they measured the subjects' leg muscles by computerized
tomography--or CAT scan. The shrinkage of muscle tissue explained at least half
of the subjects' loss of strength in those muscles.
For more information, contact
Ronenn Roubenoff, (617) 556-3172,
Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts University, Boston, MA
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Edible films made from pureed
fruits and vegetables can add shelf-life and tantalizing new flavors to lightly
processed foods such as cut produce. Some films also contain Food and Drug
Administration-approved oils and antioxidants.
An ARS food technologist developed
the films from produce like apples, oranges, carrots and strawberries. When
applied to cut apples, the thin, opaque films controlled browning and prevented
moisture loss better than several types of coatings.
An added benefit: The films could
provide new flavor combinations, such as a strawberry film on cut bananas or an
apple glaze on pork. Sheets of pureed fruit have long been available as snack
foods. But this researcher is the first to explore produce-based films to
enhance storage and flavor. ARS has applied for a patent on the edible
films.
For more information, contact
Tara McHugh, (510) 559-5864,
Process Chemistry
and Engineering Research Unit, Albany, CA
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A fast, gentle procedure called
bioimpedance spectroscopy, or BIS, may help physicians monitor treatments
designed to stop muscle loss, also called wasting. ARS nutrition researchers
have pioneered the use of BIS with healthy volunteers to measure body
composition--the amount of fat versus lean tissue, including muscle, in our
bodies. Fat-to-lean ratios are regarded as one of the best indicators of our
health, and are directly influenced by eating and exercise.
In a study led by researchers from
the University of California's San Francisco and Berkeley campuses, ARS
scientists showed that BIS can be used to gauge whether specific medication and
exercise regimens stop muscle loss in AIDS patients. BIS takes only a few
minutes and involves sending a harmless electrical current, at a range of
frequencies, from electrodes placed on the wrists and feet of the volunteer.
BIS was just as accurate, but
faster, easier, and less costly than two other approaches--DEXA (dual-energy
X-ray absorptiometry) and deuterium oxide dilution. The findings, reported in
AIDS, 1999 (vol. 13, pp. 241-248), suggest that BIS could also be used
to monitor muscle mass in other wasting diseases including cancer and
tuberculosis.
For more information, contact
Marta D. Van Loan, (530) 752-4160,
Western Human Nutrition Research
Center, Davis, CA
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The potential of different lines of
broccoli to stimulate a key enzyme that may protect against certain cancers can
vary greatly, according to a first-of-its kind study by ARS scientists in
Charleston, S.C., and researchers at Johns Hopkins University's School of
Medicine in Baltimore, Md. The scientists evaluated a diverse collection of
broccoli breeding lines.
Broccoli florets and young
seedlings are rich sources of glucoraphanin and its breakdown product,
sulforaphane. The latter compound is a potent inducer of an enzyme that
detoxifies cancer-causing compounds and inhibits early tumor growth in rodent
models. ARS scientists grew 71 USDA breeding lines of broccoli and five
commercial hybrids in the field and then took extracts from each one. Johns
Hopkins researchers measured glucoraphanin levels in these extracts and also
measured their ability to induce enzyme activity in a "test-tube"
assay.
Among the 76 broccoli varieties
evaluated, the scientists found a 30-fold variation in both glucoraphanin
levels and enzyme-induction potential. This suggests that enzyme induction may
be used to gauge a broccoli line's anti-cancer potential. At least some of the
observed variation is genetic in nature, the scientists concluded, and breeders
could exploit it to develop new varieties with greater levels of the protective
compounds. Eating such improved broccoli might stimulate an enhanced
chemoprotective response against cancer development.
Studies have shown that people who
eat cruciferous vegetables like broccoli have a lower incidence of colon and
rectal cancers. Occurring in two out of 1,000 people, these account for 15
percent of all cancer deaths.
For more information, contact
Mark Farnham, (843) 556- 0840,
U.S.
Vegetable Laboratory, Charleston, SC
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A process to make meat more tender
may also make it safer to eat. New studies show that the ARS-developed
Hydrodynamic Pressure Process (HDP) also reduces human pathogens in meat. In
the process, meat is placed in a container of water, then a small amount of
explosive is detonated to create a shock wave in the water. The shock wave
tenderizes meat by severing the stringy striations that can make meat
tough.
The scientists refined the process
using a metal, thick-walled tank imbedded in the ground. While that didn't
tenderize the meat as well as using disposable plastic containers, there seemed
to be fewer bacteria on the meat than before. So they conducted studies on
ground beef to determine the effect of HDP on naturally occurring spoilage, or
shelf-life, bacteria. The studies produced a "three-log" reduction in
shelf-life bacteria. This equates to reducing 30,000 colony-forming units
(cfu's) to 30 cfu's. A five-log reduction is the "gold standard" for bacterial
reduction, so tests are ongoing to further reduce bacterial levels.
Subsequent studies to reduce the
human pathogen Escherichia coli O157:H7 in fresh ground beef again
produced encouraging results. Ground beef that had been seeded with E.
coli O157:H7 had no detectable levels of the dangerous organism after HDP
treatment. HDP seems to inactivate most meat pathogens, such as E. coli,
but doesn't kill all bacteria, including the good Lactobacilli. Further
studies are needed to determine if HDP can be put to practical use in a
commercial setting.
For more information, contact
Morse Solomon, (301) 504-8463,
Food Technology and Safety
Laboratory, Beltsville, MD
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Do seniors maintain strong bones
after they stop taking calcium and vitamin D supplements? Researchers asked
this question after showing that men and women over 65 who took extra calcium
and vitamin D daily for three years either gained or retained bone throughout
the body and specifically in the spine and hiptwo areas prone to fracture
in elders.
Unfortunately, the benefits didn't
last. Two years after the volunteers stopped taking the required 500 milligrams
of calcium and 700 International Units of vitamin D daily, they had lost any
supplement-related benefits to the spine and hip, the researchers reported in
the American Journal of Clinical Nutrition, 2000 (vol. 72, pp. 745-750).
That's troublesome because fewer than one in 10 U.S. elders meet the current
recommendations for calcium and vitamin D. These are set at a total daily
intake of 1,200 milligrams of calcium from food and supplements and 400 to 600
I.U. of vitamin D.
Of the 389 volunteers in the
original study, 295 remained in the two-year follow-up, returning to the center
once a year for bone measurements and other tests. They no longer took calcium
and vitamin D provided by the studyalthough, for ethical reasons, they
were allowed to take their own supplements. Close to two-thirds of the women
and about half the men chose to take some supplemental calcium during the
follow-up. Vitamin D use was a little lower. But the self-selected supplements
had no impact on the results, perhaps because the amounts taken were less than
half the study levels, and use was not regular.
For more information, contact
Bess Dawson-Hughes, (617) 556-3064,
Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts University, Boston, MA
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A new kind of corn, developed by
an ARS researcher, may help ensure that people get more of the zinc they need
for good health. The new corn has about 65 percent less phytic acid, also known
as phytate, than conventional corn. That's a plus because phytate can interfere
with the body's ability to absorb certain nutrientsincluding zinc, an
essential mineral.
Physicians and scientists from the
University of Colorado Health Sciences Center in Denver, and an ARS geneticist
in Aberdeen, Idaho, collaborated on the study to test the body's ability to
absorb zinc from the low-phytate corn. Five healthy volunteers, age 23 to 39,
ate menus featuring polenta, a cooked, coarse cornmeal, for two days. Cornmeal
from the low-phytate corn was used to make the polenta one day, and cornmeal
from conventional corn was used the next. Both kinds of cornmeal were spiked
with a stable isotope of zinc that can be easily detected by laboratory
instruments.
Analysis of fecal samples showed
that the volunteers absorbed about 78 percent more zinc, on average, from the
low-phytate corn than from the conventional corn. The Colorado researchers used
the findings as the basis of a larger, follow-up study with Guatemalan
villagers.
For more information, contact
Victor Raboy, (208) 397-4162,
Small Grains and Potato
Germplasm Research Unit, Aberdeen, ID
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ARS scientists are making the job
of monitoring food, livestock feed and other materials less expensive for a
group of toxic chemicals called dioxins. The scientists have reduced the cost
of dioxin analysis from nearly $2,000 per sample seven years ago to about $600
to $800. And they are developing an even more efficient procedure that requires
minimal use of chemical solvents and is expected to reduce the current cost by
half.
Produced by both natural and
industrial processes, dioxins are chlorinated aromatic compounds that can build
up in the fat of humans and animals and may increase the risk of tumors and
have other undesirable health effects. The most likely exposure routes may
involve food products from animals that have eaten feed contaminated by the
fat-soluble chemical.
At the request of the U.S.
Environmental Protection Agency, USDA began a fact-finding mission to
investigate the extent of dioxin contamination in livestock from all sources.
ARS scientists researched dioxins in beef produced in 13 states. Nearly all the
samples were clean, with some outstanding exceptions in the kidney fat of some
individual carcasses. These came from animals raised in barns or pens
containing posts that had been treated with dioxin-containing pentachlorophenol
(penta) to prevent rotting.
Now, EPA regulations ban
penta-containing wood preservatives in fence posts or feeding troughs in barns.
And penta that is registered for sale in the United States for uses such as
preserving utility poles now must be manufactured under conditions that do not
produce the most toxic dioxin and minimize the concentration of a related
compound.
USDA's Food Safety and Inspection
Service is again surveying meats for dioxin contamination to get a better
picture of the background levels in the U.S. food supply.
For more information, contact
Janice K. Huwe, (701) 239-1288,
Animal
Metabolism-Agricultural Chemicals Research Unit, Fargo, ND
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