Attention, college students cramming between
midterms and finals: Binging on soda and sweets for as little as six weeks may
make you stupid.
A new
UCLA rat study is the first to show how a diet steadily high in fructose slows
the brain, hampering
memory and learning — and how omega-3 fatty acids can
counteract the disruption. The peer-reviewed Journal of Physiologypublishes
the findings in its May 15 edition.
"Our
findings illustrate that what you eat affects how you think," said
Fernando Gomez-Pinilla, a professor of neurosurgery at the David Geffen School
of Medicine at UCLA and a professor of integrative biology and physiology in
the UCLA College of Letters and Science. "Eating a high-fructose diet over
the long term alters your brain's ability to learn and remember information.
But adding omega-3 fatty acids to your meals can help minimize the
damage."
While
earlier research has revealed how fructose harms the body through its role in
diabetes, obesity and fatty liver, this study is the first to uncover how the
sweetener influences the brain.
The
UCLA team zeroed in on high-fructose corn syrup, an inexpensive liquid six
times sweeter than cane sugar, that is commonly added to processed foods,
including soft drinks, condiments, applesauce and baby food. The average
American consumes more than 40 pounds of high-fructose corn syrup per year,
according to the U.S. Department of Agriculture.
"We're
not talking about naturally occurring fructose in fruits, which also contain
important antioxidants," explained Gomez-Pinilla, who is also a member of
UCLA's Brain Research Institute and Brain Injury Research Center. "We're
concerned about high-fructose corn syrup that is added to manufactured food
products as a sweetener and preservative."
Gomez-Pinilla
and study co-author Rahul Agrawal, a UCLA visiting postdoctoral fellow from
India, studied two groups of rats that each consumed a fructose solution as
drinking water for six weeks. The second group also received omega-3 fatty
acids in the form of flaxseed oil and docosahexaenoic acid (DHA), which
protects against damage to the synapses — the chemical connections between
brain cells that enable memory and learning.
"DHA
is essential for synaptic function — brain cells' ability to transmit signals
to one another," Gomez-Pinilla said. "This is the mechanism that
makes learning and memory possible. Our bodies can't produce enough DHA, so it
must be supplemented through our diet."
The
animals were fed standard rat chow and trained on a maze twice daily for five
days before starting the experimental diet. The UCLA team tested how well the
rats were able to navigate the maze, which contained numerous holes but only
one exit. The scientists placed visual landmarks in the maze to help the rats
learn and remember the way.
Six
weeks later, the researchers tested the rats' ability to recall the route and
escape the maze. What they saw surprised them.
"The
second group of rats navigated the maze much faster than the rats that did not
receive omega-3 fatty acids," Gomez-Pinilla said. "The DHA-deprived
animals were slower, and their brains showed a decline in synaptic activity.
Their brain cells had trouble signaling each other, disrupting the rats' ability
to think clearly and recall the route they'd learned six weeks earlier."
The
DHA-deprived rats also developed signs of resistance to insulin, a hormone that
controls blood sugar and regulates synaptic function in the brain. A closer
look at the rats' brain tissue suggested that insulin had lost much of its
power to influence the brain cells.
"Because
insulin can penetrate the blood–brain barrier, the hormone may signal neurons
to trigger reactions that disrupt learning and cause memory loss,"
Gomez-Pinilla said.
He
suspects that fructose is the culprit behind the DHA-deficient rats' brain
dysfunction. Eating too much fructose could block insulin's ability to regulate
how cells use and store sugar for the energy required for processing thoughts
and emotions.
"Insulin
is important in the body for controlling blood sugar, but it may play a
different role in the brain, where insulin appears to disturb memory and learning," he said.
"Our study shows that a high-fructose diet harms the brain as
well as the body. This is something new."
Gomez-Pinilla,
a native of Chile and an exercise enthusiast who practices what he preaches,
advises people to keep fructose intake to a minimum and swap sugary desserts
for fresh berries and Greek yogurt, which he keeps within arm's reach in a
small refrigerator in his office. An occasional bar of dark chocolate that
hasn't been processed with a lot of extra sweetener is fine too, he said.
Still
planning to throw caution to the wind and indulge in a hot-fudge sundae? Then
also eat foods rich in omega-3 fatty acids, like salmon, walnuts and flaxseeds,
or take a daily DHA capsule. Gomez-Pinilla recommends one gram of DHA per day.
"Our
findings suggest that consuming DHA regularly protects the brain against
fructose's harmful effects," said Gomez-Pinilla. "It's like saving
money in the bank. You want to build a reserve for your brain to tap when it
requires extra fuel to fight off future diseases."
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