May Improve Cognition, Slow Aging
Eating certain foods can help protect you from heart disease,
some types of cancers and other illnesses. But can your diet also
help protect your brain if you should suffer a stroke or accidental
head injury? Or keep your thinking and memory skills strong as
Some scientists believe it might. They even think eating the
"right" foods --specifically, those high in antioxidants -- may
help defend astronauts from brain-damaging cosmic rays on future
manned missions to Mars.
New research also suggests that some of the environmental chemicals
that have gotten into many of our foods -- through the application
of herbicides and insecticides, for example, or from the leaching
of plasticizers from plastic food containers -- may be harmful
to children. This is because of the chemicals' effect on reproductive
development and their impact on brain areas involved in thinking
and learning. Still other studies are beginning to shed some light
on the neurological reasons why men tend to have an easier time
than women at losing unwanted weight.
"The role of diet in cognitive function is one of the vastly
understudied areas in the neurosciences," says Carl W. Cotman,
PhD, of the University of California-Irvine. "As these recent
studies show, significant new findings are appearing which highlight
the importance of this research on diet and cognitive function."
Eating an antioxidant-rich diet may help keep cognitive skills
strong during old age, according to a recent animal study conducted
at the University of Toronto. "We found that old dogs that were
on an antioxidant diet performed better on a variety of cognitive
tests than dogs that were not on the diet," says P. Dwight Tapp,
PhD, now of the University of California Irvine, "In fact, the
dogs eating the antioxidant-fortified foods performed as well
as young animals."
Antioxidants include vitamin E, vitamin C, and beta carotene
(a form of vitamin A), as well as other minerals and compounds
found in food. These nutrients have been shown to help reduce
oxidation, a process that can cause damage to cells and may contribute
to aging, including the reduced cognitive decline that typically
develops with age. Studies suggest that antioxidants may also
protect against certain cancers, heart disease and other non-neurological
Tapp and his colleagues used 39 beagles in their current study.
Dogs, like humans, develop a range of cognitive impairments as
they age. They lose some of their ability to learn new information,
for example, and experience more difficulty retaining information
in both short-term and long-term memory.
"Although we found that not all cognitive functions respond
to antioxidant treatment, our data suggests that antioxidants
play an important role in preventing or slowing age-related cognitive
impairments," says Tapp. Interestingly, although eating antioxidant-fortified
food improved the cognitive skills of the older dogs, we found
no improvement in the younger animals. This suggests, Tapp says,
that the diet is most effective in animals that already have some
degree of cognitive impairment. The study is currently ongoing
in the younger dogs to determine if the diet has a protective
effect on age-related cognitive decline in general.
Two years ago, researchers at the Universidad Nacional Autónoma
de Mexico (UNAM) and the University of Houston-Clear Lake (UHCL)
reported that a blueberry-enriched antioxidant diet may prevent
age-related deterioration of object recognition memory in aged
rats. Now, new findings from the same research group reveal that,
in the brains of the same rats, the diet also prevents an age-related
increase in a protein (NF-kappaB) that responds to oxidative stress,
a probable cause of brain aging.
"Our findings fit into an emerging pattern of data from many
laboratories that point to a buildup of oxidative damage as one
of the key factors in brain aging," says Pilar Goyarzu, a doctoral
student at UNAM under the direction of David Malin, PhD, and Francis
Lau. "The findings also suggest that diets rich in natural antioxidants
have the potential to slow down this damage."
For the current study, Goyarzu fed rats a blueberry-enriched
diet. NF-kappaB levels were then assayed in five different brain
regions involved in memory processes (the hippocampus, frontal
cortex, striatum, basal forebrain, and cerebellum). The aged rats
on the blueberry-enriched diet had lower NF-kappaB levels than
aged rats fed a control data. Young control rats also had lower
NF-kappaB levels than the aged control rats.
"We also found that among the aged rats, the higher the NF-kappaB
levels, the poorer their memory scores," says Goyarzu. The UNAM
and UHCL researchers are now studying the effects of aging and
diet on other proteins that mediate the effects of oxidative stress
in the brain.
At the National Institute on Aging's (NIA) Gerontology Research
Center in Baltimore, Maryland, scientists have found that blueberries
can help lessen some of the functional damage caused by a brain
injury. "Our results suggest that the consumption of blueberries
and perhaps other fruits and vegetables could have a positive
neurological impact on the aging brain, Alzheimer's disease, and
other neurological disorders," says Edward L. Spangler, the lead
author of the study.
Spangler and his colleagues fed one group of young rats a diet
supplemented with a 2 percent blueberry extract; another group
was fed the same diet, but without the extract. After two to three
months, all the animals received chemically-induced lesions in
their hippocampus, a region deep within the brain that plays an
essential role in learning and memory. Damage to the hippocampus
results in an inability to remember recent events. The researchers
then tested the animals' ability to learn a complicated maze task.
The rats that had been fed the blueberry extract were significantly
less impaired at performing the task than those that didn't receive
"We believe the blueberries contain a particular group of as-yet
unidentified bioactive chemicals that ameliorate the functional
consequences of brain damage, including a loss of the ability
to learn or remember recent events," says Spangler.
Researchers at the University of Maryland, Baltimore County
(UMBC) and the U.S. Department of Agriculture in Boston have found
that an antioxidant-rich diet may help stave off the harmful,
immediate effects of certain cosmic radiation. "These findings
may help protect future astronauts from the dangerous physical
and mental effects produced by extended radiation exposure on
long-term space missions," says UMBC's Bernard M. Rabin, PhD.
One of the biggest obstacles facing a future manned mission
to Mars is the hazard that an extended, three-years-long space
flight poses to the human nervous system. Highly radioactive,
subatomic particles known as cosmic rays can cause severe damage
to an astronaut's brain and central nervous system.
To see if antioxidants might provide future space travelers
some protection, Rabin and his colleagues fed one group of rats
a control diet and another group a diet containing either a 2
percent blueberry or a 2 percent strawberry extract for two months.
Then, using facilities at the Brookhaven National Laboratory (the
NASA Space Radiation Laboratory), the researchers exposed the
rats to the equivalent of space radiation -- 1.5 Gy of 56Fe particles.
Afterwards, the rats were put back on the antioxidant diet for
one more week before being shipped to UMBC and trained to press
a lever to receive food.
Seven months later, all the radiated animals were tested to
determine whether they were able to respond appropriately to increases
in work requirements. The control rats and those fed the antioxidant-rich
diets responded similarly. When tested again at 12 months, however,
the radiated rats that had been fed either the control or the
blueberry extract diet performed less well than those fed the
strawberry extract diet. In fact, the "strawberry" rats performed
as well as non-irradiated rats.
"These results suggest that certain antioxidant diets can prevent
some of the cognitive changes that occur with exposure to cosmic
rays," says Rabin. He and his colleagues are now studying the
effect of different antioxidant diets on other tasks and behaviors.
New studies from Florida State University (FSU) in Tallahassee,
Florida, may help explain why women are more prone to weight gain
and shed fewer pounds through exercise than men. In studies involving
male and female rats, Lisa A. Eckel, PhD, and graduate student
Shelley Moore found that females were much more susceptible than
males to overeating when presented with a sweet-tasting diet.
They also discovered that exercise helps males overcome their
urge to overeat such foods, but not females.
"When given access to running wheels, only the male rats decreased
their food intake," says Eckel. "The female rats continued to
overeat. This suggests that females are more vulnerable than males
to over eating a palatable, sweet-tasting diet."
In the past, few animal studies of overeating have involved
females, although obesity is greater in women than in men. According
to the Centers for Disease Control (CDC), 33 percent of women
in the United States are overweight compared to 28 percent of
men. For both sexes, however, obesity has become a growing and
serious health problem. CDC statistics released in 2002 showed
that the number of obese people in the United States has doubled
over the past two decades. Obesity has been linked to a host of
potentially deadly health problems, including heart disease, stroke,
diabetes and certain cancers.
One of the next steps in this research, says Eckel, is to determine
the hormonal basis for why female rats are more susceptible to
overeating than their male counterparts. "We intend to investigate
the sex differences in the release of neurotransmitters and neuropeptides
that regulate appetite and the preference for sweet tastes," she
Researchers at Mississippi State University have found that
early exposure to environmental chemicals that mimic or block
the action of the sex hormones estrogen and testosterone may disrupt
normal differences in the brain between males and females -- differences
that affect thinking and learning as well as sexual behavior.
These findings add more scientific support to the growing concern
that exposure to environmental chemicals is harmful, particularly
In recent years, scientists have increasingly linked environmental
chemicals to certain reproductive abnormalities, particularly
premature or delayed sexual development. "In the last decade,
we've also come to understand that sex hormones play an important
role in the maturation of other, non-reproductive systems," says
Russell Carr, PhD. "It's now known that estrogen is a key player
in the development of the nervous system, and that the presence
or absence of estrogen during development causes significant differences
in the brains of both male and female animals." These gender-related
differences are connected to areas of the brain involved in cognitive
as well as reproductive functions.
In their recent study, Carr and his colleagues administered
several environmental chemicals orally to newborn rats for two
weeks, beginning one day after the animals' birth. The chemicals
selected for the study were the sex hormone estradiol (E2); the
synthetic estrogen diethylstilbesterol (DES); the plasticizer
bisphenol A (BPA), which has been shown to leach out of plastics
into food; the herbicide atrazine (ATR), which has been suggested
to be estrogenic; and the insecticide methoxychlor (MC), which
mimics estrogen once it's metabolized in the body. During and
after the exposure period, the researchers measured the effects
of the chemicals on the animals' brain development. They specifically
looked for changes in the levels of the neurotransmitters dopamine,
serotonin and norepinephrine, as well as some of their metabolites,
in various regions of the brain. These levels were then compared
to levels in control animals.
At one week following the end of exposure, no significant changes
were detected in the overall levels of neurotransmitters between
the treated and the control groups. The scientists did, however,
make a startling discovery: In the control animals, there was
a significant difference between males and females in the levels
of neurotransmitters observed in two areas of the brain, the cerebellum
and hippocampus. In the treated animals, no such differences were
These findings support earlier studies from MSU that had shown
a similar gender-dependent effect of an environmental chemical
(the plasticizer BPA) on cognitive function. "This suggests that
the main effect of developmental exposure to these chemicals is
the disruption of the normal differences between males and females,"
says Carr. "It's a subtle effect because exposure to these chemicals
doesn't produce any significant effects on brain neurochemistry
within each sex."
SOURCE: Society for NeuroScience
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