If older Americans consumed extra vitamin D along with extra calcium, it
might substantially reduce the enormous cost of treating broken bones in the
elderly--estimated to be $13.8 billion in1995. That's the finding of a 3-year
study of 389 men and women over age 65. The group that took calcium and vitamin
D supplements daily had less than half as many broken bones during the course
of the study as the group that got a placebo--11 fractures versus 26. The
supplements contained 500 milligrams of calcium and 700 International Units
(IU) of vitamin D.
This substantial reduction in fractures can't be explained by the small
changes in bone mineral density between the two groups, the researchers
concluded in the New England Journal of Medicine (vol. 337, pp.670-676).
By the end of the study, the supplemented group was only slightly ahead of the
placebo group in bone mineral density, according to total body measurements and
measurements of the hip and spine. Nonetheless, some 28 million Americans who
either have osteoporosis or are at high risk can benefit from the findings. The
study is the first to demonstrate that extra calcium and vitamin D can reduce
the effect of osteoporosis in men. And it supports findings of a French study
done on elderly nursing home residents.
During the study, participants consumed a little more than 700 mg of calcium
daily from their diets. That's at the high end of the typical intake for men
and women over 65, which falls between 500 and 700 mg. By adding the
supplements, they averaged close to the 1,200 mg now recommended for people age
51 and over. To get that amount from foods, a person would need to consume a
well-balanced diet, including three sources of dairy products daily.
For more information, contact Bess Dawson-Hughes, (617) 556-3064, or
Susan S. Harris, (617) 556-3073,
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston,
MA.
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Two strawberry varieties developed by ARS scientists are rich in ellagic
acid, a natural organic compound that has been shown to inhibit certain types
of cancer. Tribute and Delite strawberries had the highest ellagic acid levels
among 36 varieties evaluated, the scientists reported in HortScience
(vol. 26, pp. 66-68). They found the acid in the strawberries' seeds and fruit
pulp, but the highest concentration was in the leaves. This information will
help them breed strawberries with higher levels in the fruit pulp.
It's not yet known how much ellagic acid must be consumed to produce
beneficial effects. But studies with the National Cancer Institute and Ohio
State's Department of Preventive Medicine recommend a diet that includes
strawberries, raspberries, blackberries, cranberries, walnuts and pecans--all
sources of the compound.
Plants produce ellagic acid and glucose to form ellagitannins--water-soluble
compounds that are easier for people to absorb in their diets. This means small
amounts of ellagitannins may be more effective in the human diet than large
doses of ellagic acid. Strawberries produce at least five ellagitannins, but
their chemical structures and their effectiveness as anti-carcinogens have not
yet been determined.
For more information, contact John L. Maas, 301-504-7653, Fruit
Laboratory, Beltsville, MD
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As people age, they may be able to reduce their risk of accumulating body
fat by eating smaller, more frequent meals. That's the message from a study
comparing the fat-burning ability of eight women in their 20s with another
eight in their 60s and 70s. While the seniors kept pace with their juniors
after eating 250- and 500-calorie meals, they couldn't match the fat-burning
rate of the younger group after a 1,000-calorie meal. Fat oxidation was about
30 percent lower in the older women after the big meal. So when older people
overindulge, the dietary fat that doesn't get burned gets stored as body fat.
On average, U.S. women in their 60s and 70s consume about 1,400 to 1,500
calories a day, according to the latest USDA survey data. So 1,000 calories is
about two-thirds of a day's calorie intake for this age group. It simulates
going out to a restaurant and having a big meal, say the researchers. They
believe the drop in fat-burning ability may be due to hormonal changes. The
older women in the study had higher levels of glucagon. This hormone triggers
the release of sugar into the blood--the opposite effect of insulin. With more
sugar available to fuel body processes, the women burned less fat.
Reported in the American Journal of Clinical Nutrition (vol 66, pp.
860-866), the study is the first to measure fat oxidation after eating and
needs confirmation in further research. It was designed to get at underlying
causes behind the age-related increase in body fat, which typically doubles
between the ages of 20 and 50 to 60 years. That increase is linked to several
diseases, including cardiovascular disease and non-insulin dependent diabetes.
The researchers recommend that seniors eat fewer calories at a sitting, but
eat more often to ensure getting enough nutrients. They also suggested that
older people exercise to increase skeletal muscle and fitness. This may offset
the fat-burning deficiency by increasing their capacity to burn fat while
resting.
For more information, contact Susan R. Roberts, (617) 556-3237,
Jean Mayer USDA Human Nutrition Research Center on Aging, Boston, MA
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New findings support the U.S. government recommendation that pregnant women
should limit supplemental iron to 30 milligrams per day unless they have
iron-deficiency anemia. Researchers from the University of California at
Berkeley, California Public Health Foundation, and ARS collaborated in the
15-month study with 13 volunteers. They monitored zinc absorption rates before
and after pregnancy. Results suggest that a nursing mother who takes high doses
of iron might interfere with her body's ability to absorb zinc.
Four of the women took supplemental iron totaling 100 milligrams a day and
had no increase in zinc absorption during lactation when the need for zinc is
the greatest. The other nine did not take an iron supplement. Their ability to
absorb zinc increased 30 percent in the final three months of pregnancy and 75
percent after 7 to 9 weeks of nursing, the researchers reported in the
American Journal of Clinical Nutrition (vol. 66, pp. 80-88). The zinc
content of breast milk didn't differ between the two groups, suggesting that
the iron-supplemented women used zinc from other tissues, such as muscles or
bone, for breast milk synthesis.
Scientists already know from animal and human studies that the body's
ability to absorb zinc changes dramatically during and after pregnancy. The new
study was the first to document the changes at intervals from pre-conception to
about 2 months after birth. It also was the first, in humans, to suggest iron
supplements might interfere with zinc absorption during lactation.
Pregnant women need zinc for normal fetal growth and development. After
their babies are born, the mother needs zinc for producing breast milk. Severe
zinc shortages can retard growth, impair brain function and reduce the body's
ability to fight infection. Many women do not consume the recommended daily
intake during pregnancy (15 milligrams) or lactation (19 mg). The richest food
sources include red meat, liver, oysters, beans, whole grains, garbanzo beans
and poultry.
For more information, contact Janet
C. King, (415) 556-9697, Western Human Nutrition Research Center, San
Francisco, CA
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A post-harvest vapor heat treatment keeps leaves of kale and collards from
yellowing and reduces their loss of sugar and other nutrients in storage. Leafy
green vegetables--rich sources of important nutrients and dietary fiber--are
highly perishable after harvest. But kale treated at 113° F for 30 minutes
remained green and crisp after 7 days in storage at 59° F. Collards, which
are more heat sensitive, maintained their freshness for a week at the same
storage temperature when first held at 104 degrees F for 60 minutes.
Scientists don't know how the heat protects the produce. But they do know
that stress from heat promotes the build-up of certain proteins. These same
"heat shock proteins" may also provide resistance to deterioration
caused by cold storage, when produce later is stored at the lower temperatures.
Further research is planned to answer these questions.
For more information, contact Chien Y. Wang, (301) 504-6128,
Horticultural Crops Quality Laboratory, Beltsville, MD
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Leptin has become a hot area for obesity research since the discovery of a
mutation in the mouse leptin gene that increases the animal's appetite while
lowering its metabolic rate. New findings, however, dampen the prospect that
this hormone-like signal may explain differences in body fat among people.
Researchers found no relationship between the amount of leptin in the blood of
61 men and women and the total number of calories they burned each day or their
metabolic rate while resting or after eating. The study volunteers ranged in
age from 18 to 81, and none were obese.
The researchers concluded in Obesity Research (vol. 5, pp. 459-463)
that leptin doesn't influence energy regulation in adults by increasing their
energy expenditure. In a study by others, young children with higher leptin
levels reportedly burned more calories during physical activity. But the recent
study indicates adults apparently lose their responsiveness to this signal.
Because leptin is produced by fat cells, the volunteers who had more body fat
also had higher blood leptin levels. But that didn't prompt them to burn more
calories.
Maintaining a stable body weight is a matter of burning as many calories as
we consume. In people whose weight control mechanism is working properly, the
body's metabolic rate automatically revs up after periods of overeating and
slows down after periods of undereating to maintain this balance. Similarly,
appetite automatically adjusts by decreasing or increasing. This process of
energy regulation is controlled by a sequence of metabolic signals. But the
details of that sequence are still sketchy. To better understand leptin's role,
the researchers examined how leptin might affect metabolic rate in adults.
For more information, contact Susan R. Roberts, (617) 556-3237,
Jean Mayer USDA Human Nutrition Research Center on Aging, Boston, MA
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Leaner pork for consumers could be a benefit of research on human obesity.
ARS scientists have been intrigued by two hormones, neuropeptide-Y and leptin.
These hormones act as signals to regulate appetite. Neuropeptide-Y, found in
the brain, is a "green light" that stimulates appetite. Leptin,
released by the fat cell, is a "red light' that signals the brain that the
body is adequately nourished and, thus, suppresses appetite. The scientists
found that giving leptin to pigs increased growth hormone secretion and made
them eat less. Theoretically, the potential exists for leaner pork because
growth hormone stimulates lean muscle growth and suppresses adipose tissue
deposition.
The scientists caution that much more needs to be learned about leptin. A
group of researchers with ARS and the University of Georgia are trying to
understand how animals process this hormone. ARS scientists in Beltsville, Md.,
are working on treatments to counter leptin's appetite-suppressing effects. ARS
colleagues in Columbia, Mo., are looking at how growing piglets use leptin.
For more information, contact C.
Richard Barb, (706) 546-3584, Richard B. Russell Research Center, Athens,
GA;
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Protein-rich foods don't prompt the loss of body calcium through the urine,
in contrast to what some health professionals have believed. A new ARS
study--confirming two other studies--finds no support for the notion that diets
containing ample meat, fish and poultry increase the risk of osteoporosis. In
the ARS study, 14 postmenopausal women excreted no more calcium when eating 10
ounces of meat, fish or poultry daily for 7 weeks than when eating only 1-1/2
ounces of these high-protein foods. Researchers attribute this to the
phosphorus in these foods, which appears to save calcium.
The belief that high-protein foods increase calcium loss came from earlier
studies in which people consumed pure protein. But it doesn't contain
phosphorus or other nutrients that may counterbalance the protein's effects,
say the researchers. The findings have an important implication for elderly
people, especially those with osteoporosis: They shouldn't limit their intake
of protein-rich foods for fear of this disease. In fact, low serum protein has
been associated with an increased risk of hip fractures. Many elderly consume
too little protein and could benefit from regularly consuming moderate amounts
of lean meat, poultry, or fish.
For more information, contact Janet R. Hunt, (701) 795-8328,
Grand Forks Human Nutrition Research Center, Grand Forks, ND
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People concerned about the safety of chromium supplements can breathe far
more easily. Every day during a 20-week study, rats consumed more than 2,000
times the estimated safe limit of chromium for people. The animals showed no
signs of toxicity as assessed by body weight, blood chemistry and tissue
analyses. Twenty weeks is about one-seventh of a rat's normal life span.
Researchers tested two widely used formulations of the mineral--chromium
picolinate and chromium chloride. While neither produced toxicity, the animals
stored more of the picolinate in their tissues, indicating that they absorbed
more. The findings, reported in the Journal of the American College of
Nutrition (vol. 16, pp. 273-279), support earlier reports of very low
toxicity in animals. And they question the relevance of a study done two years
ago using cultured human cells that reported DNA damage. Cultured cells are far
more vulnerable than body cells because they lack the body's normal protective
mechanisms.
For example, people generally absorb less than 2 percent of the chromium in
the diet; 98 percent passes in the stool. By contrast, the cultured cells were
given increasingly larger doses of chromium formulations until an effect was
observed. Years of ARS chromium studies with animals and people have not
identified any toxic symptoms, even when the chromium given was several times
above the suggested daily upper limit of 200 micrograms (mcg). In fact, the
highest daily exposure considered safe over the course of a lifetime is 350
times this upper limit. This reference dose was established by the
Environmental Protection Agency.
For more information, contact
Richard A. Anderson, (301)
504-8091, Beltsville Human Nutrition Research Center, Beltsville, MD
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The world's largest blackberry should be ready by next spring for planting
by home gardeners, pick-your-own operations and commercial growers in parts of
the West and South. Dubbed Black Butte, the berry could start showing up in
grocery store produce sections nationwide in the summer of 2000. Blackberries
are low in fat and sodium and a good source of fiber, potassium and vitamins A
and C.
Black butte's berries average 1 inch in diameter and 2 inches long and weigh
more than two-fifths of an ounce. That's almost twice the size of other
varieties of fresh blackberries, says the ARS researcher who developed the new
variety in cooperation with the Oregon Agricultural Experiment Station. Its
berries ripen in late June, four to six weeks earlier than some of the eastern
varieties. It should grow well in areas where winter temperatures stay above
10° Fahrenheit. The vines have been tested in Oregon, Arkansas,
California, North Carolina, Washington, Canada, England and New Zealand.
For more information, contact Chad
E. Finn, (541) 750-8760 or 750-8759, Horticultural Crops Research
Laboratory, Corvallis, OR
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Tomorrow's grapefruit, oranges, lemons and limes might have a powerful ally
to help them resist attack by microbes that cause costly decay. Scientists with
ARS and Texas A&M University have discovered a beneficial microbe that
fights green mold on citrus in laboratory tests. Researchers say the microbe--a
helpful strain of a fungus--is easy to raise and harvest in the laboratory, and
might someday reduce or eliminate the need for certain after-harvest
fungicides.
The fungus is named Geotrichum candidum, strain AVIR. It is a
beneficial, or avirulent, strain of the G. candidum fungus. In nature,
the wild, or virulent, fungus is the well-known cause of a fruit disease called
sour rot. Dipping, spraying or dusting fruit with a beneficial microbe to ward
off rot-causing organisms is not new, but it's a first for the avirulent G.
candidum strain. Researchers did the laboratory experiments with
grapefruits and oranges, and suspect the microbe could be employed safely and
effectively to protect other fruits as well, including apples, pears and
strawberries.
For more information, contact Cynthia G. Eayre, (209) 453-3162,
Horticultural Crops Research Laboratory, Fresno, CA
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Frazzled by the search for facts on Pfiesteria? ARS' National
Agricultural Library offers some help via the World Wide Web. The library has
produced a new web page devoted to Pfiesteria piscicida. That's the
toxic organism suspected of killing fish and generating health concerns in some
Maryland and North Carolina waterways.
The site provides links to North Carolina State University laboratories
conducting Pfiesteriaresearch, as well as other Pfiesteria
information sites. And it offers Pfiesteria fact sheets produced by
Maryland and North Carolina state agencies and a bibliography of scientific
literature on the organism. The address:
www.nal.usda.gov/wqic/pfiest.html
For more information, contact Brian
Norris, (301) 504-6778, National Agricultural Library, Beltsville, MD
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