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2006-02-01
Russell Martin
When
it comes to brain protection, there is nothing quite like
blueberries,” according to James Joseph, PhD, lead scientist in the
Laboratory of Neuroscience at the USDA Human Nutrition Research
Center on Aging at Tufts University. “Call the blueberry the brain
berry,” says Dr. Joseph.1
Dr. Joseph’s
claim was made with the publication of his landmark blueberry
research. It has since been bolstered by animal studies demonstrating
that daily consumption of modest amounts of blueberries dramatically
slows impairments in memory and motor coordination that normally
accompany aging. Moreover, a wealth of exciting new research clearly
establishes that in addition to promoting brain health, this
long-prized native North American fruit—whether consumed fresh,
frozen, canned, or as an extract—may confer a range of diverse
health benefits.
After
testing 24 varieties of fresh fruit, 23 vegetables, 16 herbs and
spices, 10 different nuts, and 4 dried fruits, the US Department of
Agriculture determined that blueberries scored highest overall in
total antioxidant capacity per serving. As most health-conscious
adults are aware by now, antioxidants are vital in countering free
radicals, the harmful byproducts of cellular metabolism that can
contribute to cancer and other age-related diseases.2
Separate
studies show that blueberries may help to lower blood cholesterol,3
promote urinary tract health, and reduce the risk of urinary
infections.4,5
Studies
in Europe have documented the relationship between consumption of
bilberries (the blueberry’s close European cousin) and eye health,
highlighting the berries’ ability to improve night vision, halt
cataract progression, and protect against glaucoma.6
New studies also support blueberries’ ability to reduce
age-associated lipid peroxidation,7
a contributor to cardiovascular disease, and to suppress the growth
of several types of cancer cells,8,9
suggesting that blueberry phytochemicals may well play a future role
in human cancer treatment. And you can add to the manifold health
benefits of blueberries at least one more reason to eat them daily:
virtually everyone agrees that they are delicious.
When
the Plymouth colonists arrived in what is now Massachusetts, native
American inhabitants shared with them the blue-tinged fruit of a low
woody shrub whose calyx forms a delicate five-point star. For
centuries, native American cultures had consumed “star berries”
not only as food but also as medicine, drinking blueberry juice to
relieve coughs, brewing a tea from blueberry leaves as a tonic, and
eating fresh, dried berries to sharpen their vision.10
Blueberries
and bilberries belong to the genus Vaccinium, which includes more
than 450 plants grown in all parts of the world. Members of the
Vaccinium genus possessing the darkest-colored fruits appear to
provide the greatest health benefits, a fact that scientists
attribute to the compounds that give the plants their dark
pigmentation. These bioflavonoids include anthocyanins and their
precursor, proanthocyanidins, both of which are voracious scavengers
of free radicals.11,12
Research demonstrates that blueberry consumption boosts serum
antioxidant status in humans.13
Elevated antioxidant levels in the body may protect against damage to
cells and cellular components, thus helping to reduce the risk of
many chronic degenerative diseases.13
How Blueberries Combat Brain Aging
In Dr. Joseph’s
groundbreaking work at Tufts, 19-month-old laboratory rats—the
equivalent of 60- to 65-year-old humans—were fed dried blueberry
extract at a dose the investigators calibrated to be the human
equivalent of one-half cup of blueberries per day. Three other groups
of rats received spinach extract, strawberry extract, or a control
diet. After eight weeks on the regimen, the investigators evaluated
the rats—now equivalent in age to 70- to 75-year-old humans—using
various tests of memory function.
Compared
to a control group fed only a standardized diet, each of the three
supplemented groups performed at least marginally better on memory
and learning tests.14
In tests of neuromotor function, however, the blueberry-fed rats
significantly outperformed the other groups. These rats were much
better able to walk the length of a narrow rod and balance on an
accelerating rotating rod compared to the other groups. This was
indeed a stunning finding, as scientists have for some time tended to
accept as established fact that age-related neuromotor dysfunction is
irreversible. Dr. Joseph’s findings appear to flatly contradict
this notion. Blueberry extract, he discovered, was clearly capable of
reversing this particular aging process as no other agent had ever
been demonstrated to do. Dr. Joseph concluded:
“This
is the first study that has shown that dietary supplementation with
fruit and vegetable extracts that are high in phyto-nutrient
antioxidants can actually reverse some of the
aging-relatedneuronal/behavioral dysfunction.” 14
Dr.
Joseph’s blueberry-supplemented rats also demonstrated improved
learning and memory skills as they navigated mazes and found—and
then remembered—the location of an underwater platform on which
they could rest from swimming. When Dr. Joseph and his colleagues
examined the brain tissues of these rats in vitro, they found that
dopamine levels were much higher than in the brains of rats in the
other groups. Dopamine is an essential neurotransmitter that enables
smooth, controlled movements as well as efficient memory, attention,
and problem-solving function. Dr. Joseph speculated that blueberry
extract might also increase brain cell membrane fluidity while
reducing levels of inflammatory compounds, thus slowing the brain’s
normal aging process.14
To
other researchers, Dr. Joseph’s study seemed especially promising
in its implications for aging humans. Older adults tend to fall or
stumble—sometimes with catastrophic consequences—because their
brains become less adept at monitoring and modulating swaying motion,
as conduction of neural signals in the brain slows with aging. Older
people likewise tend to suffer memory loss and an inability to learn
new behaviors in ways that can starkly limit their ability to lead
productive, satisfying lives. “People are told once you’re old,
there’s nothing you can do,” noted Dr. Joseph’s colleague and
study coauthor Dr. Barbara Shukitt-Hale. “That might not be
true.”15
New Studies Confirm Brain Benefits
Dr. Joseph’s
findings not only spurred scientific research into the health
properties of blueberries, but also greatly increased public
awareness of this remarkable fruit. Five important new studies
support and expand on Dr. Joseph’s original research.
In
a 2005 article published in the journal Neurobiology
of Aging,
Rachel Galli and her colleagues, also based at Tufts, reported
discovering a specific mechanism by which blueberries help reverse
the neurological aging process.16
The Galli study—which included Drs. Joseph and Shukitt-Hale as
co-investigators—sought to measure the heat-shock protein response
in the brains of both young and aged rats supplemented with blueberry
extract compared to a control group of aged rats. A protective
mechanism produced in the brains of most animals (and humans),
heat-shock proteins fight free radicals and inflammation-inducing
agents, acting similarly to antioxidants to support healthy brain
tissues. As people age, however, their ability to generate heat-shock
proteins in sufficient quantity declines,17
sometimes dramatically. The Tufts researchers sought to determine
whether blueberries could help restore the heat-shock protein
response in rats.16
After
10 weeks, the scientists subjected brain tissues from the rats to an
inflammatory challenge and then measured the subsequent heat-shock
protein response. As presumed, the brains of young rats that had
consumed blueberries produced a strong heat-shock protein response,
unlike the brains of the aged rats that did not consume blueberry
extract. The significant finding, however, was that the brains of
aged rats fed blueberries were as successful at initiating the
heat-shock protein response as the brains of young rats. The
blueberry extract proved capable of entirely restoring the heat-shock
protein response in the test animals, suggesting that blueberries may
protect against neurodegenerative processes associated with aging.16
Last
year, the journal Nutritional Neuroscience published an important new
study by scientists at the University of Barcelona. The Spanish
researchers previously had demonstrated blueberries’ effectiveness
in reversing age-related deficits in neuronal signaling. They now
sought to determine whether the active phytochemicals that give
blueberries their significant neurological benefits do indeed cross
the blood-brain barrier. Examining the brains of rats that had been
fed blueberry extract for 10 weeks, they were able to isolate
blueberry-specific agents in the rats’ cerebellum, cortex,
hippocampus, and striatum—brain areas that control memory and
learning processes. Most striking, the scientists were able to
correlate the presence of blueberry phytochemicals in the rat brain
cortices they examined with improved cognitive performance in tests
initiated at the end of the 10-week supplementation period.18
Blueberries
may also prove capable of helping humans whose brains have been
damaged by a loss of blood flow and the critical oxygen and nutrients
it provides, a condition known as ischemia (one of the two principal
causes of stroke). In a May 2005 study published in the journal
Experimental
Neurology,
researchers documented how three groups of rats whose diets were
supplemented with blueberries, spinach, and spirulina, respectively,
all suffered less brain cell loss and were better able to recover
lost function following artificially induced ischemia than rats in a
non-supplemented control group. At autopsy, the scientists observed
that the physical extent of ischemic damage to the brains of rats
that had been fed the three supplements was significantly less than
that suffered by the control group.19
Similarly,
the Tufts scientists who have been in the forefront of blueberry
research reported an additional study in the August 2005 issue of
Neurobiology
of Aging.
In this study, they demonstrated that the auditory processing speed
of aged rats supplemented with blueberries nearly matched the
lightning-fast auditory processing speeds of young rats, while the
speeds of a control group of non-supplemented aged rats were
dramatically slower. According to the researchers, “These results
suggest that the age-related changes in temporal processing speed in
[the primary auditory cortex] may be reversed by dietary
supplementation of blueberry phytochemicals.”20
Another
recent study suggests that blueberries may have applications in the
developing field of neural transplants, which many neuroscientists
believe hold promise as a means of replacing vital brain structures
destroyed or damaged by brain injury or degenerative disease.
Unfortunately, the survival of transplanted tissue is often poor,
especially in older recipients. When researchers gave blueberry
supplements to middle-aged rats receiving neural implants, the growth
of their hippocampal grafts was markedly more vigorous than that of
identical grafts in a control group, and cellular organization was
comparable to that in tissue grafted into young laboratory animals.
Blueberries may someday play an important role in ensuring that
surgically grafted tissues thrive in the new host, where they may
help to restore lost motor and cognitive functions.21
Benefits
for Other Body Systems
Blueberries’
benefits for neurological health and vigor are so well
established as to make daily consumption of the fruit a
“no-brainer” for virtually everyone. Moreover, new studies
continue to confirm blueberries’ remarkable health-promoting
effects in other areas of the human body.
For
decades, researchers in Europe have documented evidence of the
ability of bilberries to combat a range of eye disorders. During
World War II, French researchers who examined bilberry extract’s
effects in pilots found that bilberry helped improve nighttime
visual acuity, adjustment to darkness, and recovery from glare.6
In another study, all eight patients with glaucoma who were given
a single oral dose of bilberry extract demonstrated improvements
based on electroretinography, a measure of electrical
responsiveness of the retinal cells. Bilberry’s antioxidant
properties may protect against glaucoma by supporting healthy
intraocular pressure.6
In a clinical study, the combination of bilberry extract with
vitamin E stopped the formation of senile cortical cataracts in
48 of 50 patients.6
Researchers believe that the anthocyanins and proanthocyanidins
found in blueberries might similarly offer benefits for eye
health.
In
an article in the Journal
of Agricultural and Food Chemistry
in 2004, researchers announced that they had isolated three
compounds in blueberries and other dark-pigmented berries known
to lower cholesterol levels.22
In a follow-up study, one of the three
phytochemicals—pterostilbene—showed a particularly potent
effect in stimulating a receptor protein in cells that plays an
important role in lowering cholesterol and other blood fats.3
“We are excited to learn that blueberries, which are already
known to be rich in healthy compounds, may also be a potent
weapon in the battle against obesity and heart disease,” lead
author Agnes Rimando told members of the American Chemical
Society.3,22,23
Blueberry
juice or extract may help avert urinary tract infections commonly
suffered by women. Scientists formerly hypothesized that
dark-pigmented berries such as cranberry help fight infection
through an antibacterial effect caused by the acidification of
urine.4
Current research suggests that berries, including cranberry and
blueberry, may fight bacterial urinary infections by preventing
E. coli and other forms of bacteria from adhering to cells lining
the walls of the urinary tract.4,5
Blueberries
also may slow the growth of cancer cells. In 2001, University of
Mississippi researchers conducting in-vitro tests found that
blueberry and strawberry extracts were remarkably successful in
slowing the growth of two aggressive cervical cancer cell lines
and two fast-replicating breast cancer cell lines, with the
blueberry extract performing best against the cervical cancer
cells.8
Last year, a University of Georgia study similarly demonstrated
blueberry extract’s ability to inhibit cell proliferation in
two separate lines of colon cancer cells, reducing by more than
50% the rate at which the cells otherwise multiplied.9
Further studies are indicated to determine whether phytochemicals
from dark-pigmented berries may affect very early growth of
malignant cells in the bodies of humans as well.
Conclusion
Although no
studies to date have compared the relative efficacy of fresh
blueberries versus frozen berries, canned berries, or berry
extracts, each form of the fruit has been shown to contain the
essential anthocyanins and proanthocyanidins that make
blueberries one of the most exciting nutraceuticals being
researched and consumed today. Blueberry extracts have the
advantage of delivering the fruit’s phytochemicals in a simple,
standardized dose, while consuming blueberries as food offers the
benefit of flavor.
Regardless
of how they are consumed, blueberries should be considered a
mainstay of every healthy diet. This remarkable fruit, known for
centuries for its medicinal properties, continues to prove itself
in research laboratories around the world, demonstrating a wide
array of dramatic, health-enhancing benefits.
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