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If you've been having trouble concentrating,
maybe you're not getting enough of certain essential elements. Studies are
revealing new clues about the roles iron and zinc apparently play in keeping
our mental capacities—or cognitive function—up to par. Much of the
research that links inadequate nutrition to mental performance has been done
with children. But these studies were done with adults and focused on marginal
deficiencies.
 In a 20-week study with eight healthy men, the
researcher looked at the relationship between iron and the volunteers' ability
to concentrate. She found that a low score for volunteers' attention span
corresponded with a subsequent decline in iron levels in the body.
In an earlier study with 14 obese but
otherwise healthy female volunteers, she and colleagues documented a similar
change in ability to focus. The 21-week experiment showed that volunteers with
borderline anemia, as measured by blood hemoglobin, were less able to
concentrate than volunteers with higher hemoglobin. The studies are the first
in healthy adults to link a decrease in iron with a decline in attention span
and suggest that decreased ability to concentrate may be an early indicator
that an individual's iron levels are declining.
The researchers also explored the interaction
of brainpower and zinc, using the same eight men who were volunteers in the
iron study. One of the tests evaluated the volunteers' ability to recall
specific words. Preliminary results showed that, after only three weeks on a
low-zinc regimen, the ability to recall the words slowed in many of the
volunteers. Those who slowed the most also had the greatest decrease in blood
levels of zinc.
For more information, contact
Mary J. Kretsch, (530) 752-4171,
Western Human Nutrition Research
Center, Davis, CA
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Fortification of grain products with the B
vitamin folate may help reduce memory loss in the over-60 set. That's the
implication from a careful look at recent data from the third national health
and nutrition examination survey, NHANES III.
The researchers had established that
homocysteine levels were higher in elderly people with low intakes of B
vitamins, especially folate. They had also validated reports that high
homocysteine increases risk of stroke, which is a major player in the loss of
cognitive function. But they wanted to see if high homocysteine levels or low B
vitamin status had a more subtle influence in memory loss among people over age
60. That's because B vitamins are involved in the synthesis of chemicals
crucial to brain function. Or, homocysteine itself might be toxic to nerve
cells. Homocysteine is a byproduct of our own amino acid metabolism.
Fortuitously, the NHANES III included a
sensitive test of recall after a short delay—one that can identify
individuals with a milder loss of recall. It has been reported that
homocysteine is related to Alzheimer's disease, as well as to poor cognitive
function in elderly both with and without dementia. Perhaps 75 percent of
dementia is due to stroke or Alzheimer's disease, which is now thought to
develop from minor strokes.
So the researchers excluded data from people
who had suffered a stroke. Their analysis showed elevated homocysteine levels
were associated with memory loss. But the survey subjects whose blood folate
levels were in the upper half appeared to be protected from memory loss even if
their homocysteine levels were high. Reported in the American Journal of
Clinical Nutrition, 2001 (vol. 73, pp. 927-933), the findings remind us to
keep our folate levels up. And that's easy now; virtually all grain products
have been fortified with the vitamin since 1998.
For more information, contact
Martha Savaria Morris, (617)
556-3302, Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts University, Boston, MA
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A protein that helps body cells store fat
could help physicians assess whether patients whose blood vessels contain fatty
deposits called plaque are at risk for a heart attack or stroke. Researchers
found evidence that the protein—perilipin–was more actively
synthesized in ruptured plaque than in stable plaque. When plaque ruptures, it
triggers formation of a plug—an internal scab—that can stop blood
flow in the artery or reduce it to a trickle. If the ruptured plaque is in the
heart, it could cause a heart attack; if in the neck or head, a stroke could
ensue.
A physician at the ARS-funded center in
Boston collaborated on the study with a group of researchers at the University
of Maastricht in The Netherlands. The researchers wanted to know if certain
genes are more active—that is, expressed as proteins—in ruptured
plaque. They cloned genes from ruptured and nonruptured plaque and looked for
differences in expression among the genes.
There was good evidence that the perilipin
gene was turned on and expressing the protein in the ruptured plaques, whereas
it was difficult to detect any expression in stable plaques, according to the
report in Circulation Research, 2001 (vol 89, pp. 547-554).
The team's findings could have several
applications. First, a test for the presence and amount of perilipin could be
developed to detect plaque in danger of rupture. For instance, a perilipin
antibody, which would attach to the protein, could be tagged with a radioactive
tracer and "seen" with imaging technology. Such a test could be used
to monitor the effectiveness of nutritional interventions—such as folate
or antioxidants—on risk for heart attack or stroke. Also, the discovery
will help researchers better understand how plaques become unstable and could
lead to preventative measures.
For more information, contact
Andrew S. Greenberg, (617)
556-3144, Jean Mayer USDA Human Nutrition
Research Center on Aging at Tufts University, Boston, MA
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Fruits and vegetables contain a wide array of
compounds—or phytonutrients—reported to have anticancer activity in
cell cultures. Now, ARS and Clemson University scientists are probing an
assortment of berries, as well as muscadine grapes, for their ability to
inhibit the growth of breast and cervical cancer cell lines. Among U.S. women,
breast cancer is second only to lung cancer in cancer-related deaths.
The ARS scientists prepared extracts of the
berries and muscadine grapes using various solvents and different parts of the
fruit—such as juice, skin and seeds. A Clemson University colleague
assayed the extracts on the cancer cell lines. Their findings, though very
promising, are preliminary and will have to be validated in people through
clinical trials.
Various extracts from muscadine grapes,
raspberries and strawberries cut the growth of both breast and cervical cancer
cell lines by more than half. Extracts from blueberries and blackberries were
ineffective against the two cervical-cancer cell lines. But they suppressed
breast cancer cell growth—each fruit suppressing a different cell line.
Two breast cancer cell lines were used in these assays because their estrogen
requirements are different.
Specific muscadine grape extracts suppressed
a third breast cancer cell line much more than a line of healthy cells from the
same donor. That means it's more selective for cancer cells.
Cancer develops in stages. First, a normal
cell undergoes mutations. Then, mutated cells must be stimulated to keep
dividing as they get cut off from blood-delivered oxygen. Finally, more
mutations enable cells from a localized tumor to invade other tissues. The
findings reported here deal with suppression of the second stage. The
researchers are also assaying the berry and grape extracts for their ability to
prevent mutations.
For more information, contact
David E. Wedge, (662) 915-1137,
ARS Natural
Products Utilization Research Unit, Oxford, MS; or
Lyndon L. Larcom, (864) 656-7939,
Clemson University, Clemson,
S.C.
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 Potatoes are not only are tasty, they also provide a
good source of complex carbohydrates, potassium, vitamin C, folic acid and
iron. Now, studies are being conducted to examine additional health benefits of
dark-pigmented varieties not often found in the United States. That's because
brightly colored orange, red and purple potatoes might one day provide
health-promoting properties beyond those found in ubiquitous white- and
cream-colored spuds.
So far, the primary benefit likely to be
derived from boldly colored potatoes seems to be heightened antioxidant
activity. Indeed, orange-fleshed potatoes have been developed with up to four
times the antioxidants zeaxanthin and lutein as white potatoes. In addition,
the darker colored potatoes score well against other foods in a standard test
for antioxidant capacity named ORAC, or oxygen radical absorbance capacity. The
red- and purple-fleshed potatoes achieved ORAC scores comparable to
brussels-sprouts, kale, or spinach.
And the bright colors occur naturally. The
researcher identifies and selects test plants from mainstream potato breeding
programs. Still, more research must be conducted to learn about traits such as
composition and quantity of pigment, growing requirements, and yields before
colorful spuds such a these can be commercialized.
For more information, contact
Charles R. Brown, (509) 786-9252,
Vegetable and Forage Crops
Production Research Unit, Prosser, WA
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Researchers are identifying effective ways to
increase breastfeeding rates among low-income Hispanic mothers. The U.S.
Surgeon General has made increasing breastfeeding rates a public health
priority, but there has been little information about the best way to do
so—until now.
Proyecto Leche de Vida (Project Milk
of Life), a community-based pilot project, was designed to compare the
effectiveness of home visits with telephone consultations by trained
breastfeeding counselors in an area of Houston with a predominantly Hispanic
immigrant population. Preliminary results from the study, which involved 105
new mothers, are striking. A full 38 percent of mothers in the trial breastfed
exclusively for at least three months, compared to the typical five percent
rate for new mothers in that area. Breastfeeding exclusively for three months
helps reduce infant morbidity and health care costs during the first year of
life.
Researchers found that 41 percent of new
mothers who received home visits and 35 percent of those who received phone
calls still breastfed their child exclusively at three months, compared to 11
percent in the control group. First-time mothers often lack breastfeeding
knowledge and skills. Hispanic women also have limited access to
Spanish-language breastfeeding information and assistance in hospitals. So
bilingual, hands-on teaching during home visits was most effective.
After the study, the project was continued
with financial support from Episcopal Health Charities and private
philanthropists. Counselors have now provided over 2,700 breastfeeding
consultations to more than 450 women. Another 1,000 women participated in
prenatal breastfeeding classes.
For more information, contact
Judy Hopkinson, (713) 798-7000,
Children's Nutrition Research Center at
the Baylor College of Medicine, Houston, TX
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Understanding why some plants like spinach
store much of their calcium in a crystalline form could help scientists develop
more nutritious varieties of vegetables. One cup of cooked spinach contains
plenty of calcium—around 244 milligrams. But because most of the calcium
is in calcium oxalate crystals that we can't digest, humans absorb a mere 12
milligrams—or five percent.
Turnip greens, on the other hand, are nearly
crystal-free, making them an excellent source of calcium. One cup of cooked
turnip greens provides us with about as much calcium as a cup of cow's milk.
To unlock the mystery of crystal formation
and function, an ARS molecular biologist is studying a small, fast-growing
plant called Medicago truncatula. His lab has inspected thousands of
genetic variations of this simple plant, which normally stores much of its
calcium in crystals. While the genetic variants look nearly identical to the
naked eye, some have leaf cells packed with calcium oxalate crystals while
others are nearly crystal-free, the researchers reported in Plant
Physiology, 2000 (vol. 124, pp. 1097-1104).
They hope to determine whether calcium
oxalate crystals play an important role in helping plants adapt to stressful
growing conditions or fend off attacks by pathogens and insects. And they are
looking for the genes that control crystal formation. Since the plants that
don't make crystals appear to thrive as well as those that do, the researchers
should be able to breed out or remove this characteristic from M.
truncatula. If successful, this would be a first step toward making calcium
oxalate-rich vegetables like spinach a better source of calcium for humans.
For more information, contact
Paul A. Nakata, (713) 798-7013,
Children's Nutrition Research Center at
Baylor College of Medicine, Houston, TX
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Specially grown broccoli--containing hundreds
of times more selenium than grocery store varieties--protected laboratory rats
against mammary tumors in a Buffalo, N.Y., laboratory. And high-selenium
broccoli sprouts protected rats against precancerous colon lesions in a Grand
Forks, N.D., laboratory.
Published in the Journal of Agricultural
and Food Chemistry, 2001, (vol. 49, pp. 2679-2683), the findings are the
combined work of researchers at ARS' Human Nutrition Research Center in Grand
Forks, Roswell Park Cancer Institute in Buffalo, and Oregon State University in
Corvallis. Whether the findings translate to humans will require further study.
The broccoli heads and sprouts used in these
studies were produced for experimental purposes and are not available
commercially. The rats were given only enough to approximate a human dose of
about 200 micrograms daily—about three times the Reference Daily Intake.
Several human studies have shown that taking a 200 mcg-selenium supplement can
reduce the incidence of several types of cancer. But it will not reverse tumors
once they develop.
The researchers enriched broccoli because it
stores selenium in a unique form—called SeMSC for short—that is easy
for people and animals to convert into the active anticancer agent. In earlier
studies, when the Grand Forks researchers challenged rats with known
carcinogens, the animals that had eaten the high-selenium broccoli had far
fewer precancerous colon lesions than the groups given selenium salts--selenate
or selenite.
In the latest studies, the Roswell Park
researchers found a similar protective effect of high-selenium broccoli against
mammary tumors, using a rat model for such tumors. The rats got about 30 times
more selenium from the specially grown broccoli than they would in a standard
diet.
Meanwhile, the Grand Forks lab tested
high-selenium broccoli sprouts in a rat model for colon cancer and saw the same
protective effect they had earlier gotten with high-selenium broccoli. Found in
many health food stores, broccoli sprouts are known to be rich in other
anticancer compounds, but they are not enriched in selenium.
For more information, contact
John W. Finley, (701)
795-8416, ARS Grand Forks Human
Nutrition Research Center, Grand Forks, ND; or
Clement Ip, (716) 845-8875,
Roswell Park Cancer
Institute, Buffalo, NY;
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Early results with experiments using
bacteriophages to reduce foodborne pathogens and treat various poultry diseases
are encouraging. Bacteriophages—or phages for short—are viruses that
infect and kill bacteria, and a particular phage can usually infect only one or
a few related species of bacteria.
ARS researchers isolated a number of phages,
that would target a particular strain of E. coli that causes an air sac
infection, called air saculitis, in broiler chickens. The disease leads to
death or condemnation of the carcasses during processing, and is very difficult
to treat.
When the scientists mixed a bacteriophage
with the E. coli strain—serotype 02—before they challenged
broiler chickens with the bacteria, the animals were completely protected from
respiratory infection. The researchers suspect other phage strains may be even
better suited to prevent air saculitis. And they recently began to investigate
the effectiveness of phages to treat the infection in poultry and perhaps
become an alternative to antibiotic use.
The scientists are also investigating the
efficacy of phages against other foodborne pathogens, such as Salmonella
and Campylobacter. In cooperation with the University of Arkansas, they
isolated phages effective against Salmonella. Phages were first
discovered in 1915, but research on their therapeutic use was largely abandoned
outside of Eastern Europe when antibiotic drugs became widely available in the
1940s.
For more information, contact
William E. Huff, (501) 575-2104,
Poultry Production and Product Safety
Research Unit, Fayetteville, AR
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