Soy protein may be an important ally in lowering cholesterol. New findings
indicate that it can enhance the effects of a diet designed to lower
cholesterolboth for men whose levels are in the safe cholesterol range
and for those above it.
The study involved 26 men, 20 to 50 years of age, half of whom had high
cholesterol. All consumed the National Cholesterol Education Program's Step I
diet to lower their cholesterolbut with a special twist. Half of the
subjects were getting their protein from soy; half from meat. Then, after a 10-
to 15-week "washout" period, the two groups switched diets; those
getting soy switched to meat and vice versa.
Men who began the study with elevated cholesterol had a 13 percent drop in
the artery-damaging LDL cholesterol while consuming the soy protein and only an
8 percent reduction while eating meat protein. Even the men who began the study
with cholesterol levels in the safe range differed in LDL reduction from the
two types of protein. With soy protein, their LDL dropped 11 percent compared
to 5 percent with meat. Both groups improved more with soy protein regardless
of their age or weight. The findings will be in an upcoming issue of the
American Journal of Clinical Nutrition.
The study's design may also explain why previous studies have produced
conflicting evidence concerning the merits of soy protein. Researchers
suggested that previous studies finding little benefit from soy may not have
included a washout period or adequately monitored subjects' diets. The men in
this study ate only prepackaged meals prepared at the center.
For more information, contact William
W. Wong, (713) 798-7168, Children's
Nutrition Research Center at Baylor College of Medicine, Houston, TX.
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Foodborne bacteria that were previously subjected to lower heating
temperatures may be tougher to kill, a new study shows. E. coli 0157:H7
bacteria that sustained a sublethal dose of heat were more heat- resistant than
bacteria that were not exposed to such heat. The results strongly suggest that
cooking regimes designed to kill E. coli and other foodborne pathogens
be based on the pathogen being in its most heat-resistant state.
The researchers heated beef gravy samples contaminated with E. coli
0157:H7 to 115 degrees F for 15 to 30 minutes. The heat was not sufficient to
kill the bacteria. But it was enough to stimulate an adaptation to the
stressful heating conditions. The researchers continued cooking the gravy to a
final internal temperature of 140 degrees F. Preheated E. coli survived
1.5 times longer at the higher temperature than E. coli not subjected to
sublethal temperatures. And the increased heat tolerance lasted for at least 48
hours.
The findings, published in the Journal of Applied Microbiology (vol.
84, pp. 677-684), have implications for food processors: Slowly heating foods
to the final cooking temperatures normally used may not kill bacteria. Such
conditions may occur in refrigerated, cook-in-bag foods such as filled pasta,
beef stew, roasts and soups. The slow heating rate and low heating temperatures
widely used to prepare these foods may make potential pathogens more heat
resistant.
For more information, contact Vijay K. Juneja, (215) 233-6500,
Eastern Regional Research Center,
Wyndmoor, PA.
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A new, rapid, easy-to-use test that detects E. coli 0157 in food
products is from 10 to 100 times more sensitive than other tests for the
sometimes deadly bacterium. And it works on hamburger meat. An ARS biochemist
developed the test using equipment and technology patented by IGEN
International, Inc., of Gaithersburg, Maryland.
The test uses magnetic beads coated with antibodies to E. coli
0157and antibodies labeled with ruthenium. This metal, through a chemical
reaction, emits light that helps detect the presence of E. coli. No
special training is necessary to conduct the inexpensive test. The equipment,
including a computer, can fit on a small table. And 50 samples can be tested in
an hour. Total time from sample to answer: only 6-8 hours. A graphic
presentation about the test is on the Internet at
http://craw.arserrc.gov/ecolitest/index.htm.
A large commercial meat supplier is evaluating the test. From the new assay,
IGEN hopes to develop a line of fast, highly sensitive tests that will help
food producers detect contaminants.
For more information, contact C.
Gerald Crawford, (215) 233-6628, Eastern
Regional Research Center, Wyndmoor, PA.
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A natural compound in fish and meats improved two cardiovascular health
indicators in six study volunteers. When these volunteers ate foods enriched
with an omega-3 fatty acid called DHA, they had an increase in HDL
cholesterolthe kind known to protect against heart disease. And blood
fats known as triglycerides decreased by about 26 percent, the researchers
reported in Lipids (vol. 32, pp.1137-1146).
The volunteers on the high-DHA regimen also showed an increase of about 69
percent in apoprotein-E, a compound that carries cholesterol to the liver for
breakdown and excretion. An apo-E increase had not been reported in other DHA
studies with humans, according to the study leader. The study was designed to
distinguish the effects of DHA from those of another omega-3 fatty acid, EPA.
Both occur in fish oils thought to have cardiovascular benefits.
Ten healthy, non-smoking men age 20 to 39 lived at the research center for
the four-month investigation. Scientists added about a teaspoon of DHA-rich oil
to salad dressings or bean, salsa or guacamole dips served to six volunteers,
substituting safflower oil in the servings for other men. DHA is short for
docosahexaenoic acid.
For more information, contact Gary J. Nelson, (415) 556- 0899,
Western Human Nutrition
Research Center, Presidio of San Francisco, CA.
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A diet rich in leafy green and yellow-orange vegetables and fruits, whole
grains, raisins and nuts supplies plenty of antioxidants. Twelve women, ranging
from 34 to 84 in age, relaxed their own antioxidant defenses when they switched
to this diet from a typical western diet--high in refined foods and low in
fruits and vegetables.
ARS scientists collaborated on the study conducted at the private SPHERA
Foundation in Los Altos, California. To assess the antioxidant power of each
diet, they measured two enzymes that protect cells against oxidative damage. A
copper-containing enzyme, superoxide dismutase, dropped by two-thirds when the
women ate the plant-rich diet. The selenium-containing enzyme, glutathione
peroxidase, dropped by one-third.
For four weeks, the volunteers consumed all the white bread, pasta, pastry,
snack foods, convenience foods, meat, fish, poultry, eggs and dairy their
hearts desired. But they had to limit fruits and vegetables to two servings a
day, avoiding leafy green and yellow varieties altogether.
Then, for four weeks, they ate at least six servings daily of green and
yellow fruits and vegetables. They switched to whole grain bread and ate as
many other whole grains and legumes as they desired. In addition, every day
they downed two tablespoons each of almonds, hazelnuts, pecans, and sesame oil
(tahini); a tablespoon of wheat germ oil for cooking or dressing foods; three
small boxes of raisins; and a cup of ginger tea and two cups of green tea.
Refined products and reduced-calorie and fat-free products were verboten, as
were fried foods. Eggs were allowed, but meat, fish and poultry were limited to
a meager 3 ounces per week. Dairy products could have no more fat than 1
percent.
While most research is being done on the health benefits of a few plant
compounds, the researchers advise that the epidemiologic evidence for health
benefits is associated with diets rich in fruits and vegetables, not individual
compounds.
For more information, contact
Leslie M. Klevay, (701)
795-8454, Grand Forks Human Nutrition
Research Center, Grand Forks, ND; or Gene A. Spiller, (650) 941-7251, SPHERA
Foundation, Los Altos, CA.
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Processing improved the ability of wheat bran to reduce an indicator of
colon cancer in a study of rats. Wheat bran heated and shaped into short,
crispy strips for a commercial breakfast cereal was more effective than raw
wheat bran in reducing aberrant crypt foci, or ACF, which signal colon cancer
in people as well as laboratory animals. The animals fed processed wheat bran
had 33 percent fewer aberrant crypt foci in their colons than rats fed raw
wheat bran. All had been injected with a chemical that stimulates formation of
ACF.
Colorectal cancer is the second deadliest cancer in the U.S., killing nearly
55,000 Americans every year. Researchers have known for more than a decade that
feeding raw wheat bran to lab animals reduces the occurrence of ACF. Bran is
the thin, fiber-rich outer layer of the wheat kernel.
Researchers with ARS and the University of California at Davis conducted the
6 1/2-month study, which was partly funded by Kellogg Co. They fed 120 white
lab rats a diet that included either processed or raw wheat bran. For the
study, the processed bran was heated and shaped in a food-processing machine
known as an extruder.
For more information, contact Wallace
H. Yokoyama, (510) 559- 5695,
Western Regional Research
Center, Albany, CA.
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A small study may help settle the controversy over whether HIV-infected
people can improve their natural antioxidant status by taking supplements of
the amino acid cysteine. The findings, soon to be published in the American
Journal of Physiology, indicate that they might.
People with HIV are known to develop lower levels of the antioxidant
glutathione (GSH). And those with low glutathione levels get more secondary
infections and cancers and have a higher mortality rate. Some studies have
shown that a form of cysteine called NAC (N-acetylcysteine) boosts GSH levels.
Others have suggested that NAC is ineffective. A large industry is built around
selling GSH and NAC supplements.
Researchers asked five HIV-infected volunteers with no symptoms of AIDS to
take NAC supplements for one week. Their glutathione-making efficiency
increased by 40 percent, equaling the synthesis rate in five normal, healthy
individuals. And the amount of glutathione in their blood cells increased by 15
percent in a week's time. This confirms other findings in the U.S. and in
Brazil, Mexico and Germany that NAC is helpful.
The study also explains why people with HIV have low glutathione. It appears
that the HIV-infected volunteers sometimes were producing the antioxidant too
slowlyrather than using it too quickly. The researchers reached this
conclusion after comparing GSH synthesis rates in the five HIV-infected
research volunteers and five healthy participants. They used amino acids tagged
with stable isotopeseasily traced, non-radioactive forms of
elementsto study how the body synthesizes GHA.
For more information, contact Farook
Jahoor, (713) 798-7084, Children's
Nutrition Research Center at Baylor College of Medicine, Houston, TX.
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It's easier to limit your intake of trans fats and soften their effect on
the heart with new margarines that have been hardened without partial
hydrogenation. The new spreads evolved from findings by ARS scientists and
others. In the ARS study, researchers looked at the effects of butter and two
margarinesone made without trans fatson blood lipids of 46
volunteers in a 15-week study.
Not surprisingly, butter evoked the highest total cholesterol and
artery-damaging LDL cholesterol levels. After consuming a margarine containing
trans fats for 5 weeks, the volunteers' total cholesterol was 3.5 percent
lowerand LDL was 5.4 percent lowerthan with butter. Five weeks of
eating the margarine without trans fats made an even bigger dent in blood
lipids. Compared to levels with butter, total cholesterol and LDL were 4.7 and
6.7 percent lower, respectively. The findings are reported in the American
Journal of Clinical Nutrition (vol. 68, pp. 768-777). The changes were
larger than could normally be expected, because the volunteers consumed three
to four times more of the spreads than the average American.
The researchers conclude that people would be wise to limit trans fats
wherever they can--as long as they don't replace these with heart-damaging
saturated fats. Trans fats make up an estimated 2 to 3 percent of total
calories in the U.S. diet. And most of that comes from partially hydrogenated
oils in margarines, shortening in baked goods, and restaurant-fried foods.
The study's trans-fat-free margarine had 21 percent saturated fat, compared
to 16 percent for typical margarine and 53 percent for butter. More than half
the saturated fat in the trans-fat-free margarine, however, was stearic acid,
which doesn't raise blood lipids.
For more information, contact Joseph Judd or
David Baer, (301) 504-9014,
Beltsville Human Nutrition
Research Center, Beltsville, MD.
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New findings suggest that African American women living in the northern
latitudes may benefit from increasing their vitamin D intake. The vitamin is
essential for absorbing calcium and thus is integral to strong bones. But the
African American women in an ARS study had about half as much 25-
hydroxyvitamin Dthe most sensitive measure of D statuscirculating
in their blood throughout the year as the white women. The African Americans
also had smaller increases in circulating vitamin D during summer. Sunlight
stimulates skin to make the vitamin, but pigmented skin makes less.
Researchers measured indicators of bone health in 90 healthy, young
women51 African American and 39 whiteliving in the Boston area. In
the winter when vitamin D levels are lowest, an important hormone called
parathyroid hormone was elevated only in the African American women. This
hormone signals that blood calcium is low, and it can stimulate loss of calcium
from the bones.
The African American women got nearly as much vitamin D and calcium from
food and supplements as the white women. So intake was not a major factor in
the racial differences, the researchers reported in the American Journal of
Clinical Nutrition (vol. 67, pp. 1232-1236). Apparently, African American
women living in northern latitudes don't manufacture enough vitamin D during
the summer to carry them through the winter months, the researchers concluded.
For more information, contact Susan Harris, (617) 556-3073, or
Bess Dawson-Hughes, (617) 556-3064,
Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts, Boston, MA.
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High blood pressure and teen pregnancy are the top health problems in the
U.S. Delta region, according to a survey of 500 community leaders there. The
survey, which covered 36 counties in Mississippi, Louisiana and Arkansas, also
showed that leaders in all three states think residents eat too many high-fat
foods. The leaders included ministers, public health officials, teachers and
other individuals with a knowledge of their towns. They were asked to rate the
top health and nutrition problems and speculate on their causes.
Arkansas leaders rated teen pregnancy as the top health problem; the other
two states cited high blood pressure. For nutrition, high-fat foods topped the
list, followed by too much fast food and a lack of nutritional information.
The survey was the work of the Delta Nutrition Intervention Research
Initiative (Delta NIRI). ARS and six universities in the three states joined
forces to create the project to identify nutrition and health problems in Delta
communities and find ways to help solve them. The survey of community leaders
is a first step. It tells Delta NIRI members what programs would be
well-received and effective. Residents are now answering diet and health
questions to validate the community leaders' perspectives.
Compared with national figures, average birth weight is lower in the Delta
region, and Delta families have higher rates of infant mortality and
cardiovascular disease. The Delta poverty rate averages 29 percent versus the
12-percent national average.
For more information, contact Margaret Bogle, (501) 954-8882,
USDA-ARS Delta NIRI, Little Rock, AR.
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A bacterium patented by ARS to reduce Fusarium dry rot in stored
potatoes has proven 50 percent more effective than a synthetic chemical now
used to control rot in commercial storage bins. The chemical, thiabendazole
(TBZ), is the only federally registered fungicide for potatoes destined for
human consumption. Dry rot fungi plague the potato industry worldwide, causing
a dark tissue discoloration on the potato that eventually forms a dry, crumbly
rot. Annual losses in stored potatoes in the United States are estimated at
more than $100 million.
Scientists with ARS, the University of Idaho and United Agri Products, Inc.,
of Greeley, Colorado, tested potentially protective bacteria on bin-stored
potatoes at four North Dakota and Idaho sites. A report on the studies is in
Phytopathology (vol. 87, pp. 177-183).
The most outstanding bacterium tested was a strain of Enterobacter
cloacae. It reduced dry rot an average of 21 percent in contrast to 14
percent by TBZ. And ARS scientists have shown the microbe can be produced in a
liquid culture system compatible with industrial fermentation practices. It is
one of 18 bacteria ARS patented as dry rot inhibitors. The agency is seeking to
license the microbes or form cooperative agreements to develop biocontrol
products.
For more information, contact
David A. Schisler or
Patricia J. Slininger, (309)
681-6567, National Center for Agricultural
Utilization Research, Peoria, IL.
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