For
centuries, people have enjoyed blueberries for their flavor and color.
In a new research study, animals fed a blueberry extract diet, rich
in naturally-derived antioxidants, showed fewer age-related motor
changes and outperformed their study counterparts on memory tests.
Indeed, blueberries and other foods containing antioxidants may act
to protect the body against damage from oxidative stress, one of several
biological processes implicated in aging and in the development of
a number of neurodegenerative diseases. The National Institute on
Aging (NIA) and the U.S. Department of Agriculture funded the study.
In the
study, three groups of older rats were fed an 8-week-long diet supplemented
with fruit or vegetable extracts with potential antioxidant effects.
A fourth group of animals did not receive the special diet. The group
of animals that received the supplements showed some improvement on
key indicators of age-related decline.
The
study was conducted by James Joseph, Ph.D. of the U.S. Department
of Agriculture, Human Nutrition Research Center on Aging at Tufts
University in Boston, and Paula C. Bickford, Ph.D. of the University
of Colorado Health Sciences Center and the Department of Veterans
Affairs Medical Center in Denver. The study results appear in the
September 15, 1999, issue of the Journal
of Neuroscience.
The
animals that received supplements were given either blueberry, strawberry,
or spinach extracts. Investigators found that the group of rats that
was fed blueberry supplements came out on top in tests of balance
and coordination. The two groups given strawberry or blueberry supplements
showed the most compelling evidence of protection against oxidative
stress in their brains. On tests of working memory, all three groups
receiving supplements outperformed their control counterparts. fn
addition, the groups receiving supplements all showed signs of the
presence of vitamin E, a key antioxidant, in their brains.
"The
exciting finding from this study is the potential reversal of some
age-related impairments in both memory and motor coordination, especially
with blueberry supplements," said Molly Wagster, Ph.D., a Health
Scientist Administrator with the NIA's Neuroscience and Neurospsychology
of Aging Program. "For these animals at least, investigators
were able to produce a noticeable improvement within a relatively
short period of time. A next important step in the research will be
to see if the improvements are long lasting."
When
a cell converts oxygen into energy, tiny molecules called free radicals
are made. When produced in normal amounts, free radicals work to rid
the body of harmful toxins, thereby keeping it healthy. When produced
in toxic amounts, however, free radicals damage the body's cellular
machinery, resulting in cell death and tissue damage. This process
is called oxidative stress.
"Whether
results found in this study will also prove true for humans remains
to be seen," says Marcelle Morrison-Bogorad, Ph.D., who directs
the NIA's Neuroscience and Neuropsychology of Aging Program. "The
only way to determine whether particular food ingredients actually
work to slow age-related cognitive decline in humans as well is to
conduct controlled clinical trials." The NIA has recently funded
additions to two ongoing clinical trials testing whether a number
of over-the-counter agents, including antioxidants such as vitamin
E, influence the rate of cognitive decline in older women.
Plant
chemicals, called phytochemicals, are present in fruits and vegetables
and may have additional beneficial propertie,5 beyond the antioxidant
activity. The authors believe that the phytochemicals present in blueberries,
strawberries, and spinach may have properties that increase cell membrane
fluidity, allowing important nutrients and chemical signals to pass
in and out of the cell, thereby reducing inflammatory processes in
tissues.
Recent
studies suggest that a diet rich in fruits and vegetables---natural
dietary sources of antioxidants--may have a beneficial anti-cancer
effect. Orange and yellow vegetables, fruits, and whole grains are
all rich in natural antioxidants. Several currently popular substances,
including vitamin E, beta carotene, vitamin C, and selenium, are also
thought to have antioxidant effects in the body, but how they actually
work is not entirely understood. Scientists are studying the effectiveness
of these and other agents for their antioxidant properties and for
their ability to protect cells against damage and death associated
with oxidative stress.
"When
we hear these promising results, we also may hear an echo of our wise
mothers' voices-Eat your fruits and vegetables," says Dr. Wagster.
The
National Institute on Aging, part of the National Institutes of Health
(NIH), located in Bethesda, Maryland, leads the Federal effort supporting
basic, clinical, epidemiological and social research on aging and
the special needs of older people.
Reference:
* Joseph,
J.A., Shukitt-Hale B., Denisova, N.A. Bielinksi D., Martin, A., McEwen,
J.J., and Bickford, P.C. "Reversals of Age- Related Declines
in Neuronal Signal Transduction, Cognitive, and Motor Behavioral Deficits
with Blueberry, Spinach, or Strawberry Dietary Supplementation."
Journal of Neuroscience, September 15, 1999, Vol. 19, No. 18, pp.
8114-812 1.
