Chlorine levels recommended for swimming pools and water parks may
not be high enough to kill a parasite that causes diarrhea, according
to ARS experts in the parasite Cryptosporidium parvum. This single-celled
organism is transmitted in the feces of infected people and animals.
Infection occurs by ingesting oocysts. Because the oocysts are small
and resistant to chlorine, standard filtering and chlorination may not
be effective. Cryptosporidium has caused numerous recent outbreaks
in recreational water, such as swimming pools and water parks, often
visited by diapered children.
In collaboration with the Centers for Disease Control and Prevention
(CDC), ARS researchers tested water that had fecal matter added to simulate
conditions in a contaminated swimming pool. When the water contained
this organic matter, currently recommended levels of chlorine did not
kill the parasite, the researchers reported in Emerging Infectious
Diseases, 1999, (vol. 5). That's because organic material deactivates
some of the chlorine. Swimming pools are likely to contain hair, skin
cells, suntan lotion, algae or leaves, and sometimes urine and fecesall
of which can decrease the effectiveness of chlorine. Previous tests
showing that recommended chlorine levels are adequate had been conducted
in clean water.
Based on the ARS findings, CDC suggests changes in engineering of public
pools and water parks, such as improved filtering and more frequent
turnover of the water. It also suggests changes in pool policies, such
as requiring diapered children to wear rubber pants or "swim diapers."
And it recommends educating staff and visitors about the following simple
measures for preventing waterborne disease transmission:
- Stay out of the pool while ill with diarrhea and for several days
afterward
- Try not to swallow pool water
- Use safe diaper changing and hand washing practices
- Give young children frequent bathroom breaks
- Encourage swimmers to shower before entering a pool
For more information, contact Ronald Fayer, (301) 504-8750, or James
Trout, (301) 504-8496, Immunology
and Disease Resistance Laboratory, Beltsville, MD
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To guard against osteoporosis, people may be wise to eat more fruits
and vegetables as well as dairy products. Recent research finds a significant
association between intakes of potassium, magnesium and fruits and vegetableswhich
are good sources of the mineralsand a measure of bone strength
in elderly men and women.
Researchers at the ARS/Tufts center in Boston and at Harvard Medical
School analyzed data from 907 members of the original Framingham Heart
Study345 men and 562 women. They were looking for correlations
between the elders' intakes of each mineral and of fruits and vegetables
in general with bone mineral density measurements at the hip and wrist.
They found correlations across the boardwith potassium alone,
magnesium alone, potassium and magnesium together and fruits and vegetables
together. Men and women with high intakes had stronger bones, the researchers
reported in the American Journal of Clinical Nutrition, 1999
(vol. 69, pp. 727-736).
Bone is living tissue. Its density is constantly affected by diet and
exercise. Fruits and vegetables may help prevent the loss of bone minerals
by counteracting the acid environment generated during normal digestion.
When the body's environment is acidic, minerals are believed to be drawn
out of the bone to neutralize the acid, thereby reducing bone strength.
It is also possible that potassium and magnesium have direct effects
on bone cells, the researchers conjecture.
They also analyzed data from a smaller group229 men and 399 womenlooking
for changes in bone mineral density over time. In measurements four
years apart, they found a slowing of bone loss in men but not
womenlinked to potassium and magnesium levels, separately and
together, as well as fruits and vegetables.
Fruits and vegetables provide one-third of the potassium in the U.S.
diet and a little more than one-fifth of the magnesium. Good sources
of potassium include bananas, oranges, tomatoes, potatoes, broccoli
and melon. Good sources of magnesium include a variety of whole foods
including fruits and vegetables, milk, fish and whole grains.
For more information, contact Katherine Tucker, (617) 556-3351, Jean
Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston,
MA
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If you go on a low-fat diet, you will surely lower your cholesterol
count, right? Not necessarily, according to an ARS study. Among 11 healthy
men aged 20 to 35 who volunteered for the study, cholesterol levels
didn't change significantlyregardless of whether the men were
on a low-fat or high-fat regimen. Fat calories made up 39 percent of
the day's total calories in the high-fat menus, while accounting for
only 22 percent during the low-fat regimena cut of nearly half.
Why didn't such a drastic drop in fat intake lead to a similar decrease
in cholesterol? The researchers contend that it was because they didn't
change the ratio of fatsthat is, saturated to polyunsaturated
to monounsaturated. The fat profile in both diets was 28 percent saturated
fatthe kind in butter or lard; 33 percent monounsaturated fat;
6 percent monounsaturated trans fats, as are found in some margarine;
and 29 percent polyunsaturated fatsthe kind in healthful cooking
oils. Other minor fatty acids made up the remaining 4 percent. The findings
are reported in Lipids, 1995 (vol. 30, pp. 969-976).
All volunteers ate the high-fat diet for 20 days, Then, six volunteers
ate low-fat meals for 50 days, while the other five volunteers ate the
high-fat foods: whole milk instead of nonfat, and cream cheese rather
than jelly, on their breakfast bagels, for example. After that, the
two groups crossed over to the opposite menus for the final 50 days
of the study.
For more information, contact Gary J. Nelson, (530) 752-5356, Western
Human Nutrition Research Center, Davis, CA
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Is depression in women of childbearing age linked to low iron reserves?
No, according to a recent study that found no relationship between mood
and marginal iron status. That's different from severe iron deficiency,
which can cause depression.
About one in five women of childbearing age has low iron stores, compared
to one in 60 men. Twice as many women as men are clinically depresseda
gender difference that begins in adolescence. Depression is more pronounced
among married women ages 25 to 45 with children. But earlier studies
on the subject produced conflicting findings. So a nutritionist and
a psychologist checked 384 women, ages 20 to 45, who were not diagnosed
as depressed.
Unlike some earlier studies, they used a standardized psychological
profile and mood checklist to test the volunteers. They also analyzed
the volunteers' blood samples by the most sensitive tests of iron stores.
They found no relationships between mood scores and three signs of iron
statusserum ferritin, serum iron and hemoglobin, the researchers
reported in Behavioral Medicine, 1999, (vol. 25, pp. 62-68).
Serum ferritin is the first indicator of iron status to drop, while
hemoglobin is the last and most resistant indicator to change. Iron
deficiency severe enough to cause depression and fatigue would show
up in a simple hemoglobin or hematocrit test, the researchers say.
For more information, contact Janet R. Hunt, (701) 795-8328, Grand
Forks Human Nutrition Research Center, Grand Forks, ND
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A variation in the gene that enables vitamin D to attach to cells
predicts differences in dietary calcium absorption and bone density
in healthy children, researchers recently found. Other studies have
shown that the variation, called the ff genotype, is associated with
lower bone mass in adults and children. The variation is in the Fok1
site of the vitamin D receptor gene. The new finding, showing that people
with certain genotypes absorb calcium less efficiently, is a step toward
understanding why some groups appear more likely to develop osteoporosis,
the researchers say.
They studied the relationship between the three genetic variations
of Fok1, known as FF, Ff and ff, and markers of calcium status in 72
healthy children between 7 and 12 years of age. The children were tested
for calcium absorption, bone mineralization and bone density.
Those with the FF genotype absorbed over 40 percent more calcium from
their diet than those with the ff genotype and 17 percent more than
those with the Ff genotype. The FF genotype children also had significantly
greater bone density measurements, the researchers report in the Journal
of Bone Mineral Research, 1999 (vol. 14, pp. 740-746). Peak bone mass
occurs in early adulthood and is considered an important determinant
of osteoporosis risk later in life.
For more information, contact Steven
A. Abrams, (713) 798-7124, Children's Nutrition Research Center at Baylor
College of Medicine, Houston, TX
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Extra iron is part of physicians' nutritional strategies for newborn
premature infants. But they disagree on whether their tiny patients
should get the iron along with their formula or between feedings. A
new study concludes iron-fortified formulas are a good option.
While the researchers found that premature infants had a very small
increase in iron that was given separately, it is not significant compared
to the extra effort required and the possible stomach irritation that
can come with a separate supplement. It is simpler and effective to
use iron-enriched formulas for premature infants when breast feeding
isn't an option. The findings are reported in Pediatric Research,
1998 (vol. 44, pp. 507-511).
Pediatric nutritionists have long agreed that extra iron can also push
up red blood cell production. As a result, many milk formulas designed
for preemies are fortified with iron. But the researchers wanted to
know if the high levels of calcium in preemie infant formulas interfere
with iron absorption. They traced red blood cell iron use in 13 premature
infants given both kinds of iron treatments. They used stable isotopes
of iron to compare the rate that the infants' bodies used the iron in
formulas versus separate supplements.
For more information, contact Steven
A. Abrams, (713) 798-7124, Children's Nutrition Research Center at Baylor
College of Medicine, Houston, TX
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ARS and University of Illinois scientists are combing through leftovers
from soybean oil and protein extraction, searching for components that
might help people stay cancer free. The idea is to add DNA-friendly
compoundsor chemoprotectantsto foods and pharmaceuticals.
Some natural and synthetic chemicals cause DNA breakage that can result
in malignancies, but chemoprotectants help prevent irreversible cell
damage.
The soy leftovers consist of a gooey molasses that has been used as
livestock feed. A light brown powder called phytochemical concentrate
(PCC), isolated from the molasses, contains a mixture of these potent
materials. About 30 percent of the PCC powder are isoflavonessome
of which are already known to inhibit cancer. In fact, specific isoflavones
are already being marketed as food additives. Saponinsfoaming
agents often found in detergentsmake up another 30 percent of
the PCC powder, while the remaining 40 percent is a mix of sugars and
other substances. ARS researchers are separating PCC into different
fractions for biological assays at the University of Illinois.
In one assay, they look for changes in DNA damage to individual hamster
ovary and lung cells. The saponins, they report in Teratogenesis,
Carcinogenesis and Mutagenesis, 1999 (vol. 19, pp. 121-135), are
proving to be quite effective at preventing DNA damage by a known carcinogeneven
more so than the isoflavones. A mixture of soy saponins, all derivatives
of soyasapogenol b, completely prevented DNA damage by the carcinogen,
which was a compound commonly found in charred meat at relatively low
levels.
In another assay, they look for changes in growth of human colon tumor
cells. So far, they have tested only the isoflavone fractions and found
genestein most effective at suppressing cell growth.
Chemoprotectants isolated from these leftovers could become, pound
for pound, more valuable than the main processed soy products, the researchers
say. They note, however, that at high doses some of these protectants
can have the opposite effectactually increasing DNA damage. So
care must be taken in gathering all the data needed to prevent public
exposure to harmful levels in foods or pharmaceuticals. This research,
supported in part by the United Soybean Board, may serve as a model
for research on other foods.
For more information, contact Mark
A. Berhow, (309) 681-6595, National
Center for Agricultural Utilization Research, Peoria, IL; or Michael Plewa, (217) 333-3614, Department of
Crop Sciences, University of Illinois, Urbana-Champaign
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A new USDA database on the World Wide Web will help scientists pinpoint
which of the estrogen-like compounds in soy foods may be responsible
for a lower risk of cancer, especially breast cancer. Some of these
compounds, known as isoflavones, have also been reported to benefit
the cardiovascular system or to reduce bone loss after menopause. The
new database is on the web at: http://www.nal.usda.gov/fnic/foodcomp/Data/isoflav/isoflav.html.
ARS scientists compiled the database, which gives values for the major
isoflavones in 128 soy foods and ingredients. Isoflavones, such as daidzein,
genistein and glycitein mimic the hormone estrogen. They also have antioxidant
capability and may perform other functions that enhance health.
The researchers evaluated and compiled some 30 scientific reports of
the isoflavone content of foods. And they relied heavily on analyses
by a collaborator at Iowa State University in Ames. Commercial products
were analyzed to arrive at isoflavone values for some types of foods
or food additives. The database gives isoflavone values for some individual
brand names.
The database springs from a larger effort by the researchers to compile
information on health-enhancing phytonutrients in foods. It follows
on the heels of a database of carotenoidssuch as beta and alpha
carotene, lycopene and luteinin 215 foods launched last fall.
Future plans include a database for food flavonoids, such as catechins
in tea, naringin and taxifolin in citrus, and quercitin in onions, apples
and red wine.
For more information, contact Gary Beecher, (301) 504- 8356, or
David Haytowitz, (301) 734-5635, Beltsville Human Nutrition Research
Center, Beltsville and Riverdale, MD; beecher@bhnrc.usda.gov. dhaytowitz@rbhnrc.usda.gov
Back to Contents
Treating alfalfa seeds and sprouts with a combination of irradiation
and chlorine effectively safeguards them against E. coli O157:H7
and Salmonella, researchers found. Not only did the dual treatment
kill both organisms, it extended the shelf life of sprouts from about
five days to more than a week. This is good news for sprout growers.
Since 1995, raw alfalfa sprouts have been recognized as a source of
foodborne illness in the United States, with several outbreaks of both
E. coli O157:H7 and Salmonella. Since sprouts can't withstand
abrasive physical washing because of their fragility, cleaning the seed
has become the primary focus.
Along with irradiation, the researchers subjected alfalfa seeds to
three concentrations of calcium hypochloritea chlorine source.
A 3-percent weight-per-volume concentration equals about 20,000 parts
per million of available chlorine. When the pH is neutral, the 2.5-
and 3-percent concentrations reduced E. coli O157:H7 by 99.99
percent. The pH level is important because when the solution is more
alkaline, such as pH 10, the chlorine would change to a form that would
be less effective against bacteria.
According to the scientists, the best way to eliminate pathogens would
be a combination of irradiation and sanitation treatments. That's because
sprouts and seeds may be contaminated internally, which would prevent
a surface disinfectant from working effectively. In the tests, the scientists
used the irradiation dose approved for meat. The U.S. Food and Drug
Administration has approved ionizing radiation as a safe and effective
food preservation tool. The research is part of an effort by a task
force of representatives from several federal agencies and industry
to find ways to control microbial contamination of sprouts .
For more information, contact Donald
W. Thayer on irradiation, (215) 233-6582 and William
F. Fett on chlorination, (215) 233-6418, Eastern
Regional Research Center, Wyndmoor, PA
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Changing the levels of a key hormone in tomatoes could lead to fruit
that tastes better and lasts longer. Such a tomato could be on the market
in about three years, the scientists estimate. The scientists genetically
altered the levels of auxin, a hormone that causes a tomato to grow
and ripen. It's also known as the youth hormone because it keeps plants
in a more youthful state.
Scientists have been studying auxin for more than 120 years. They've
been able to change auxin levels, but the changes were expressed throughout
the plant, not just in the fruit. The aim is to control the hormone
production so that it can be introduced into specific targeted tissuessuch
as the fruit without affecting the growth processes in other parts
of the plant.
The researchers inserted a backward copy of a corn geneiagluinto
a tomato. In its normal sequence, the iaglu gene reduces free auxin
levels. The reversed gene, however, counteracts the tomato iaglu gene,
thereby increasing auxin levels. This slows the ripening process and
keeps tomatoes "youthful" longer. Because the gene was put
in with a fruit-specific promoter, only the tomato fruit was affected.
For more information, contact Jerry
D. Cohen, (703) 306-1442, Horticultural
Crops Quality Laboratory, Beltsville, MD
(on detail to the National Science Foundation until October 1999)
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